METAL ALLOY COMPOSITION, METHOD OF FABRICATING THE SAME, AND PRODUCT COMPRISING THE SAME
Disclosed are a metal alloy composition including an amorphous or crystalline metal matrix and metal particles having hyperelasticity by a phase transition dispersed in the metal matrix, wherein the metal alloy composition includes at least one early transition metal (ETM), at least one late transition metal (LTM), and silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %, a fabricating method thereof, and a product including the same.
This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0040326 filed in the Korean Intellectual Property Office on Mar. 29, 2017, and Korean Patent Application No. 10-2018-0035248 filed in the Korean Intellectual Property Office on Mar. 27, 2018, the entire contents of which are incorporated herein by reference.
BACKGROUND 1. FieldA metal alloy composition, a method of fabricating the same, and a product including the same are disclosed.
2. Description of the Related ArtRecently, a metal material as an exterior material for an IT device such as a smart phone and a laptop has drawn much attention. In particular, a plastic material was mainly used as an IT device exterior material for a mobile in the early years in consideration of flexibility and weight of the device, but it is currently being replaced with a lighter metal material in order to differentiate a product and improve an aesthetic appearance thereof.
An aluminum alloy and a magnesium alloy currently used for a metal case have a light weight but low strength, and a limit in molding through plastic deformation. In addition, the aluminum alloy may realize various colors but is difficult to surface-modify up to a micro- or nano-scale and particularly, has remarkably deteriorated scratch resistance characteristics and bending resistance characteristics and thus may be easily damaged by an external impact such as falling.
The above metal case is mostly produced through die casting or a computer numerical control (CNC) process. The die casting has high productivity and high dimensional precision, but has a drawback of low product strength and difficulty of surface treatment. The CNC process may be advantageously used to process a complex shape but requires a plurality of steps, for example, greater than or equal to 20 steps, and thus has very low productivity, and accordingly, development of a material and a process capable of minimizing the number of molding steps is required.
SUMMARYA metal alloy composition having shape-controlling ability and glass-forming ability, and a method of fabricating the same are disclosed.
In addition, a product having improved mechanical characteristics using the metal alloy composition is provided.
According to an embodiment, a metal alloy composition includes: an amorphous or crystalline metal matrix; and a metal particle having hyperelasticity by phase transition dispersed in the metal matrix, wherein the metal alloy composition includes at least one early transition metal (ETM), at least one late transition metal (LTM), and silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %.
A supercooling liquid region of the metal alloy composition may be about 40 K to about 100 K.
The early transition metal may be selected from titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), hafnium (Hf), molybdenum (Mo), tantalum (Ta), chromium (Cr), yttrium (Y), and tungsten (W).
The late transition metal may be selected from nickel (Ni), iron (Fe), copper (Cu), cobalt (Co), copper (Cu), and manganese (Mn).
A ratio of the atomic number of the late transition metal relative to a sum of the atomic numbers of the early transition metal and the late transition metal may range from about 0.4 to about 0.6.
The metal alloy composition may be represented by Chemical Formula 1.
(TixZr1-xNiyCu1-y)100-a-bSiaAb [Chemical Formula 1]
In Chemical Formula 1, A is at least one element selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga), 0.25≤x≤0.45, 0.3≤y≤0.5, 0<a<2, and 0≤b≤2.
A martensitic transformation stress of the metal particle may be about 1000 MPa to about 2300 MPa.
A maximum recovery stress of the metal particle may be about 1500 MPa to about 2500 MPa.
A maximum recovery strain of the metal particle measured under an 8% strain condition may range from about 5% to about 8%.
The metal particle may have an austenite phase at about 0° C. to about 50° C.
The austenite phase may be transited into one phase of a B19 phase, an R phase, and a B19′ phase by stress application.
The austenite phase may be transited into a B19′ phase by stress application, and may be recovered to the austenite phase by removal of the applied stress.
A temperature corresponding to a crossing point of the metal particle between a plastic deformation critical stress curve and a martensite phase induction critical stress curve depending on temperature changes may be greater than about 50° C., and
the martensite transformation starting temperature, martensite transformation finishing temperature, austenite transformation starting temperature, and austenite transformation finishing temperature may be less than about 0° C.
A product composed of the metal alloy composition is also provided.
A thickness of the product may be greater than or equal to about 100 micrometers.
A method of fabricating the metal alloy composition includes fusing a parent alloy including at least one early transition metal (ETM), at least one late transition metal (LTM), and silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %, solidifying the melted parent alloy at a supercooling liquid region between a glass transition temperature and a crystallization temperature to produce an amorphous metal alloy, and heat treating the amorphous metal alloy to form an amorphous or crystalline metal matrix and a metal particle dispersed in the metal matrix and having hyperelasticity characteristics.
While producing the amorphous metal alloy, an amorphous fraction of the produced amorphous metal alloy may be greater than or equal to about 70 volume %.
The amorphous fraction of the produced amorphous metal alloy may be about 100 volume %. That is, the produced amorphous metal alloy may be completely amorphous.
While fusing the parent alloy, elements of the parent alloy may be melted using an arc melting method.
The parent alloy may further include at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga).
Before heat treating the amorphous metal alloy, the produced amorphous metal alloy may be further molded into a predetermined shape.
A metal alloy composition having shape-controlling ability and glass-forming ability and a method of fabricating the same may be provided. A product having improved mechanical characteristics by including the metal alloy composition may also be provided.
Exemplary embodiments of the present disclosure will hereinafter be described in detail, and may be easily performed by a person having ordinary skill in the related art. However, this disclosure may be embodied in many different forms, and is not to be construed as limited to the exemplary embodiments set forth herein.
In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.
As used herein, “amorphous” refers to a solid phase in a disordered state similar to a liquid phase, since internal metal atoms are not regularly aligned when a melted metal is being quenched at a speed that is higher than or equal to a threshold cooling speed and is thus solidified to form an amorphous phase.
As used herein, “self-healing” refers to recovery of original properties of a material, as a part of the material damaged by external heat and mechanical impact is recovered by itself without any external interference or through external triggering.
As used herein, “glass-forming ability (GFA)” is a reference showing how easily an alloy of a particular composition becomes amorphous.
Hereinafter, a schematic structure of a metal alloy composition according to an embodiment is described.
Referring to
The metal alloy composition 10 may be a bulk type. The metal alloy composition 10 may be molded into a ribbon shape, a rod shape, or a sheet shape, or may be molded into various other shapes as needed regardless of such shapes.
The metal alloy composition 10 may be a metal alloy wherein a whole or a part thereof is sintered at a supercooling liquid region between a glass transition temperature and a crystallization temperature.
The metal matrix (MM) may be amorphous or crystalline. That is, the metal matrix (MM) may be completely amorphous, partly crystalline, or completely crystalline.
The properties of the metal matrix (MM) may be controlled by a fabricating process of an amorphous metal alloy or a heat-treatment process which will be described later. For example, the metal matrix (MM) is completely amorphous and crystalline metal particles (MD) are dispersed therebetween as shown in
The metal matrix (MM) according to an embodiment may have an amorphous fraction of greater than or equal to at least about 60%, greater than or equal to at least about 70%, greater than or equal to at least about 80%, or greater than or equal to at least about 90%, or for example, as shown in
As described above, when the completely amorphous metal matrix (MM) is formed first and the crystalline metal particle (MD) is grown by the subsequent heat-treatment, a degree of formation of the crystalline metal particle (MD) inside the metal matrix (MM), a crystal lattice structure of the crystalline metal particle (MD), and properties thereof may be precisely controlled.
In addition, a product wherein formation of the crystalline metal particle (MD) is precisely controlled through such a method may express hyperelasticity characteristics completely, even if the product has a thickness of several micrometers or greater, scores of micrometers or greater, or even hundreds of micrometers or greater.
However, an embodiment is not limited thereto, and during the metal matrix formation, the metal matrix (MM) may be filled with metal particles (MM) having complete crystallinity as shown in
On the other hand, the metal particle (MD) according to an embodiment may be crystalline. The metal particle (MD) may include a crystalline phase having hyperelasticity characteristics so that metal alloy composition 10 according to an embodiment may exhibit a hyperelasticity behavior.
A phase having the hyperelasticity behavior may be an austenite phase. In an embodiment, the metal particle (MD) may have an austenite phase at a temperature of about 0° C. to about 50° C.
The crystalline phase having hyperelasticity characteristics may undergo phase transition between a martensite phase and an austenite phase at a temperature of around room temperature, or about 0° C. to about 50° C., and may be a phase having self-healing characteristics in the phase transition at room temperature.
In an embodiment, the metal particle having a hyperelasticity phase by the phase transition is dispersed in the metal matrix (MM), and thereby when a deformation or scratch occurs at at least one part of the metal matrix (MM), the amorphous metal alloy composition 10 may self-heal the deformation or scratch based on the hyperelasticity phase of the metal particle (MD).
The austenite phase may be a parent phase of the metal particle (MD), and according to kinds of alloys of the metal particle (MD), it is determined whether it is a martensite phase or an austenite phase.
For example, in the case of a Ti—Ni based metal alloy composition, the B2 phase that is an austenite phase is a parent phase, and an R phase, a B19′ phase, or a B19 phase may be a martensite phase. That is, the austenite phase may be transited into one phase of a B19 phase, an R phase, and a B19′ phase by application of a stress.
For example, the austenite phase may be transited into the B19′ phase by stress application and may be recovered to the austenite phase as removal of the applied stress.
The phase transition may occur by applying a stress to the austenite phase at around room temperature.
The metal particle (MD) may have a sphere shape, a needle shape, or a wire shape, but an embodiment is not limited to such a shape.
The metal particle (MD) may be completely isolated from adjacent metal, or adjacent metal particles may contact each other or be agglomerated with each other by growth of grains to provide a grown crystal. As described above, a metal alloy composition 10″ wherein the metal matrix (MM) is filled with the metal particle (MD) may be obtained.
Hereinafter, the hyperelasticity behavior of the metal particle (MD) is briefly described.
For example, in the case that the metal alloy composition 10 according to an embodiment is a Ti—Ni based alloy, the metal alloy composition 10 may have a phase transition 100 from a B2 phase into a B19 phase, a phase transition 200 from a B2 phase into a B19′ phase, a phase transition 300 from a B2 phase into an R phase, a phase transition 400 from an R phase into a B19′, and a phase transition 500 from a B19 phase into a B19′ phase. Among them, the phase transition 200 from the B2 phase into the B19′ phase has a relationship with a shape memory effect and a hyperelasticity effect.
In
The martensite transformation starts at Ms, and the martensite transformation is finished at Mf, that is, a phase transition from the austenite phase (B2 phase) to the martensite phase (B19′ phase) may be completed, and the austenite transformation starts at As, and the austenite transformation is finished at Af, that is, a phase transition from the martensite phase (B19′ phase) to the austenite phase (B2 phase) may be completed.
Referring to
Next, during cooling 511 of the austenite phase 501, the austenite phase 501 is phase-transited into a twinned martensite phase 512, the twinned martensite phase 512 is phase-transited into a detwinning martensite phase 514 in response to a stress 513 applied to the twinned martensite phase 512, the detwinning martensite phase 514 is phase-transited into a twinning martensite phase 516 if the stress applied to the detwinning martensite phase 514 is removed 515, and during heating 517 of the twinning martensite phase 516, the twinning martensite phase 517 is transformed into the austenite phase 501 to have the austenite phase 501. The flows of 511 to 517 are referred to as a shape memory effect.
If the room temperature (T2) is relatively far greater than the austenite transformation finishing temperature (Af), a stress to induce plastic deformation is lower than a stress to induce a martensite phase when a stress is applied, and thus a deformation behavior occurs through plastic deformation (e.g., slip deformation) and a martensite transformation does not occur.
On the other hand, when the room temperature (T2) is relatively only a little greater than the austenite transformation finishing temperature (Af), the metal particle (MD) may have the martensite phase 503 through a martensite transformation when a stress is applied. Thereafter, when the stress is removed, it may be reversed into the B2 phase through a reversible reaction because the B2 phase is stable at room temperature. Such a deformation behavior may be defined as hyperelasticity.
Accordingly, so that such a metal particle (MD) may have hyperelasticity characteristics, a temperature (Md) corresponding to a crossing-point (P) of a plastic deformation critical stress curve (A) and a martensite phase induction critical stress curve (B) depending on temperature changes of the metal particle (MD) may be greater than about 50° C. or greater than or equal to about 60° C., and the martensite transformation starting temperature (Ms), the martensite transformation finishing temperature (Mf), the austenite transformation starting temperature (Af), and the austenite transformation finishing temperature (Af) may be less than about 0° C. or less than or equal to about −10° C.
As described above, an initial state may be determined to be a B2 phase or a B19′ phase according to the temperature of martensite phase transformation (e.g. Af, As, Mf, or Ms) relative to room temperature. A shape memory effect may occur when the room temperature is lower than Mf and may be a phenomenon wherein the initial state is the B19′ phase, then the B19′ phase is deformed by a stress application, and is phase-transited into the B2 phase through heating, thereby being recovered to an original shape.
On the other hand, the hyperelasticity characteristics may occur when a use temperature range of about 0° C. to about 50° C. is higher than Af and an initial state is a B2 phase, and may be a phenomenon wherein the B2 phase is phase-transited into a B19′ phase by a stress application through martensite transformation and the B19′ phase is again phase-transited into the B2 phase because the B2 phase is stable at about 0° C. to about 50° C., thereby being recovered to an original shape. Therefore, so as to have hyperelasticity characteristics, a phase transition temperature such as Mf and Af needs to be controlled to be room temperature or less, for example less than or equal to about 0° C.
In an embodiment, a martensitic transformation stress of the metal particle (MD) may be, for example, greater than or equal to about 1000 MPa, greater than or equal to about 1100 MPa, greater than or equal to about 1200 MPa, greater than or equal to about 1300 MPa, greater than or equal to about 1400 MPa, or greater than or equal to about 1500 MPa, and for example, less than or equal to about 2300 MPa, less than or equal to about 2200 MPa, less than or equal to about 2100 MPa, or for example about 1000 MPa to about 2300 MPa, about 1400 MPa to about 2200 MPa, or about 1500 MPa to about 2100 MPa.
Herein the martensitic transformation stress refers to a stress at which an austenite phase is deformed into a martensite phase exceeding an elastic deformation of the austenite phase itself, when a stress is applied to the austenite phase.
A maximum recovery stress of the metal particle (MD) may be, for example, greater than or equal to about 1500 MPa, greater than or equal to about 1600 MPa, greater than or equal to about 1700 MPa, or greater than or equal to about 1800 MPa, and for example, less than or equal to about 2500 MPa, less than or equal to about 2400 MPa, less than or equal to about 2300 MPa, or less than or equal to about 2200 MPa, or for example, about 1500 MPa to about 2500 MPa, about 1700 MPa to about 2300 MPa, or about 1800 MPa to about 2200 MPa.
Herein, the maximum recovery stress refers to a stress at which a martensite phase that is plastic-deformed by a stress is not recovered to an austenite phase when the stress is removed.
On the other hand, the maximum recovery strain of the metal particle under an 8% strain condition may be, for example, greater than or equal to about 5%, greater than or equal to about 6%, greater than or equal to about 7%, or greater than or equal to about 8%.
Herein the 8% strain condition refers to a recovery degree when a compression stress is applied to the metal particle until an 8% strain is reached and then the stress is removed, and under the 8% strain condition, a measurement value may be about 0% to about 8%.
When the recovery strain is less than or equal to about 5%, deformation performance may be limited.
In this way, the metal particle (MD) may exhibit an excellent hyperelasticity behavior within the ranges of the martensitic transformation stress and the maximum recovery stress. The metal particle (MD) may also exhibit excellent recovery characteristics when the strain is greater than or equal to about 5% under the 8% strain condition.
Accordingly, when a product is fabricated using the metal alloy composition 10, the product also has excellent hyperelasticity due to the metal alloy composition 10.
Hereinafter, a specific composition wherein a product fabricated using the metal alloy composition 10 has excellent hyperelasticity is described.
The metal alloy composition 10 may include at least one early transition metal (ETM) and at least one late transition metal (LTM). The early transition metal may include at least one selected from titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), hafnium (Hf), molybdenum (Mo), tantalum (Ta), chromium (Cr), yttrium (Y), and tungsten (W), and the late transition metal at least one selected from nickel (Ni), iron (Fe), copper (Cu), cobalt (Co), copper (Cu), and manganese (Mn).
In this way, when the metal alloy composition 10 is a multi-component composition including at least one early transition metal and at least one late transition metal, glass-forming ability of the metal alloy composition 10 may be improved.
In an embodiment, the at least one early transition metal may be selected from titanium (Ti) and zirconium (Zr), or may be selected from titanium (Ti), zirconium (Zr), and hafnium (Hf).
In an embodiment, the at least one late transition metal may be selected from nickel (Ni) and copper (Cu).
However, an embodiment is not limited thereto, and as long as the metal particle (MD) exhibits the hyperelasticity characteristics, various combinations of the early transition metal and the late transition metal may be included.
In an embodiment, an atomic ratio of the late transition metal relative to a sum of the early transition metal and the late transition metal in the metal alloy composition 10 may be, for example, greater than or equal to about 0.3 or greater than or equal to about 0.4, and for example, less than or equal to about 0.7 or less than or equal to about 0.6, or for example about 0.4 to about 0.6, or about 0.5.
For example, when the atomic ratio of the late transition metal relative to a sum of the early transition metal and the late transition metal in the metal alloy composition 10 is 0.5, an atomic ratio (atomic %) of the early transition metal to the late transition metal may stoichiometrically be about 1:1.
When the atomic ratio of the late transition metal relative to a sum of the early transition metal and the late transition metal in the metal alloy composition 10 is out of the range, a different phase that is not an austenite phase to control a hyperelasticity behavior may be formed in the metal particle (MD).
In an embodiment, the metal alloy composition 10 may include silicon (Si) in an amount of greater than 0 atomic % and less than about 2 atomic %. The silicon is an additional element for improving the glass-forming ability of the metal alloy composition 10. In an embodiment, the metal matrix (MM) may be completely amorphous by the additional element during formation of the metal alloy composition 10.
In order to form a completely amorphous metal matrix, the additional element may constitute a multi-component of three or more components along with the early transition metal and the late transition metal, or may satisfy a specific heat of mixing and atomic size relationships in a relationship with the early transition metal and/or the late transition metal.
For example, sizes of the early transition metal and/or the late transition metal of the metal alloy composition 10 may be greater than or equal to about 10%, or for example, greater than or equal to about 12%, relative to the size of the additional element.
On the other hand, heat of mixing (ΔHmix) of the additional element with each of the early transition metal and the late transition metal of the metal alloy composition 10 may be less than or equal to about 0, or may have, for example, a negative value.
Interactions between the early transition metal and/or the late transition metal may be suppressed by controlling sizes and/or heat of mixing of each element during formation of the metal matrix. Accordingly, a completely amorphous metal matrix is prepared and thereby unintentional crystallization may be suppressed before the subsequent heat-treatment.
Specifically, the silicon (Si) may have a difference of heat of mixing with the late transition metal element or the early transition metal element in the metal alloy composition 10, which is less than or equal to about −20 KJ/mol, except copper (Cu). The silicon (Si) may have a smaller atomic radius than the late transition metal element and/or the early transition metal element.
For example, titanium (Ti) has an atomic radius of 147 pm, zirconium (Zr) has an atomic radius of 160 pm, nickel (Ni) has an atomic radius of 124 pm, and copper (Cu) has an atomic radius of 128 pm, but silicon (Si) has an atomic radius of 118 pm that is somewhat small. In addition, heat of mixing (ΔHmix) of silicon (Si) with titanium (Ti) has a negative value of −49 KJ/mol, heat of mixing (ΔHmix) of silicon (Si) with zirconium (Zr) has a negative value of −67 KJ/mol, heat of mixing (ΔHmix) of silicon (Si) with nickel (Ni) has a negative value of −23 KJ/mol, and heat of mixing (ΔHmix) of silicon (Si) with copper (Cu) has a negative value of −2 KJ/mol.
Accordingly, silicon (Si) according to an embodiment may suppress unintentional crystallization during cooling of the melted parent alloy during the formation of the completely amorphous metal matrix.
When the metal alloy composition 10 according to in an embodiment includes silicon (Si) in an amount of greater than or equal to about 2 atomic %, silicon solubility by the early transition metal and the late transition metal in the austenite phase may be exceeded. In this case, the metal particle may have different phases separate from the austenite phase in addition to the austenite phase during formation of the metal particle through subsequent heat-treatment of the metal matrix.
These different phases work as a pinning site of a grain boundary motion, and thus may hinder recovery of a metal alloy composition after deformation. Accordingly, when the metal alloy composition includes these different phases, it may fail to show desired hyperelasticity characteristics.
However, the metal alloy composition 10 according to an embodiment includes silicon within above range and thus may have a high fraction of the austenite phase and even the austenite phase as a single phase.
On the other hand, a metal is required to have a thickness of greater than or equal to about 100 micrometers, for example, greater than or equal to about 300 micrometers, in order to be used as an IT device exterior material for a mobile. Herein, as early transition metals are unintentionally crystallized with late transition metals during cooling of a melted parent alloy, a crystalline phase may be unintentionally formed inside a metal matrix. The unintentional crystallization may more highly occur as a thickness increases, and the reason is that a cooling speed difference between the surface and the center during cooling of the melted parent alloy increases.
The unintentionally formed crystalline phase hinders a viscoelastic behavior of the metal matrix in a supercooled liquid region during the subsequent heat-treatment. Accordingly, shape-controlling ability of the metal alloy composition may be deteriorated.
In addition, even though a completely amorphous metal matrix is formed by adding the above additional element, the additional element may have an influence on forming a different phase from the austenite phase in the subsequent heat-treatment. Accordingly, shape-controlling ability of the metal alloy composition may be deteriorated.
Therefore, the present inventors found that the metal alloy composition 10 according to an embodiment may have excellent glass-forming ability and simultaneously shape-controlling ability as described above by controlling an amount of silicon (Si) in a range of greater than about 0 atomic % and less than about 2 atomic %.
As a result, a product fabricated to have a thickness of greater than or equal to about 100 micrometers by using the metal alloy composition 10 according to an embodiment may show an excellent hyperelasticity behavior.
The metal alloy composition according to an embodiment may further include at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga). These elements, like silicon (Si), may similarly suppress the crystallization of early transition metals and late transition metals during cooling of the melted parent alloy or expand a supercooled liquid region of an amorphous matrix and thus perform a function of adjusting molding in the supercooled liquid region.
The supercooled liquid region of the metal alloy composition 10 according to an embodiment may have a range of about 40 K to about 100 K. When the metal alloy composition 10 has a supercooled liquid region of less than about 40 K, a sufficient viscoelastic behavior for molding or casting the composition into a desired shape is difficult to secure, but when the metal alloy composition 10 has a supercooled liquid region of greater than about 100 K, a temperature and time for dispersing a crystalline phase having hyperelasticity characteristics in the metal alloy composition 10 become larger, and thus process efficiency may be deteriorated.
The metal alloy composition 10 according to an embodiment may be represented by Chemical Formula 1.
(TixZr1-xNiyCu1-y)100-a-bSiaAb [Chemical Formula 1]
In Chemical Formula 1,
A is at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga),
0.25≤x≤0.45, 0.3≤y≤0.5, 0<a<2, and 0≤b≤2.
Recently, an amorphous alloy as a material capable of minimizing molding steps has been introduced. The amorphous alloy shows a viscoelastic behavior in a supercooled liquid region between a glass transition temperature at which viscosity starts to sharply decrease and a crystallization temperature at which an amorphous state starts to be crystallized, and thus may be easily molded into a desired shape.
Accordingly, a manufacture process of the amorphous alloy in a supercooled liquid region may have higher dimensional precision than with die casting and higher productivity than in a CNC process.
However, glass-forming ability of this amorphous alloy needs to be improved in order to secure a commercializable thickness of greater than or equal to about 100 micrometers.
Accordingly, the metal alloy composition 10 according to an embodiment improves glass-forming ability of an amorphous metal matrix by precisely controlling an amount of silicon (Si) as described above, and in addition, provides a method of improving shape-controlling ability by increasing an austenite phase-forming ratio in a subsequent heat-treatment process. The metal alloy composition 10 according to an embodiment may be prepared to have a thickness of hundreds of micrometers, but the metal alloy composition 10 itself and a product formed thereof may still show an excellent hyperelasticity behavior.
When the metal alloy composition 10 according to an embodiment is partially deformed or scratched, metal particles (MD) adjacent to at least the deformed or scratched region have a phase transition from an austenite phase to a martensite phase to suppress a spread of the deformation or the scratch.
Since this scratch or deformation in the metal alloy composition 10 is recovered through the self-healing function, a life-span of a material may not only be remarkably expanded, but also many economic and environmental advantages may be obtained.
Hereinafter, a product composed of the metal alloy composition is briefly described.
According to an embodiment, a product composed of the metal alloy composition 10 may be provided. The product may be formed by molding the metal alloy composition 10 into a ribbon shape, a rod shape, or a sheet shape, or into various shapes as needed, regardless of such shapes as described above.
The product according to an embodiment may have one of a ribbon shape, a rod shape, and a sheet shape. According to an embodiment, the product may have a sheet shape.
A product according to an embodiment may exhibit an improved hyperelasticity behavior even if the thickness is greater than or equal to about 100 micrometers, for example greater than or equal to about 200 micrometers, greater than or equal to about 300 micrometers, greater than or equal to about 400 micrometers, or greater than or equal to about 500 micrometers, as described above.
The hyperelasticity behavior of the product may depend on a glass-forming ability during initial formation of the metal alloy composition 10 and an austenite phase fraction according to a subsequent heat-treatment as described above. Among them, the shape of the product may have an effect on the glass-forming ability and the subsequent heat-treatment.
For example, when the product has a two-dimensional shape, for example, a sheet-shape, the product is cooled down at a slow speed compared with when it has a one-dimensional shape, and thus glass-forming ability of a metal alloy composition forming the product is relatively deteriorated.
In addition, as a thickness of the product is increased, there may be a cooling speed difference between on the surface and the center of the product, which may deteriorate the glass-forming ability of the metal alloy composition forming the product, and simultaneously reduce a fraction of an austenite phase formed through the subsequent heat-treatment in the metal alloy composition.
In other words, glass-forming ability of the metal alloy composition may vary depending on a desired shape of the product, and particularly, when the product has a sheet-shape (two-dimensional shape) with greater than or equal to a predetermined thickness (e.g., greater than or equal to hundreds of micrometers), glass-forming ability and/or shape-controlling ability may be deteriorated by the above factors.
However, even though a product according to an embodiment has a sheet-shape having a thickness of hundreds of micrometers, it may be manufactured by using a metal alloy composition having excellent shape-controlling ability and glass-forming ability as described above. As a result, an embodiment may provide a product having excellent hyperelasticity regardless of a thickness and/or a shape.
Accordingly, the product may be applied or used for various metal products requiring a self-healing function without a limit regarding a thickness and/or a shape, for example, an exterior material for an IT device such as a mobile phone, a smart phone, and a tablet PC, a hot water-controlling valve, a spring for a house, a fire door, a cantilever valve for preventing a burn, a shower valve for preventing a burn, a fire damper, a joint of a high pressure oil pipe, an orthopedic bone fixation device, a stent for general surgery, a guide wire, a robot actuator, a muscle wire, a satellite antenna, an electrical connector of a missile navigation system, various wire couplings, and a DMB antenna, and for various industries such as a sliding actuator of a sliding phone, a neckband, a headset, a glasses frame, a bra wire, a neurosurgical spinal fixation device, an orthodontic brace wire, and a fishing rod. However, use of the product is not limited to the above applications.
In addition, the product may be used for an environmentally meaningful technological leap along with the active worldwide research tendency on improvement of fuel efficiency and development of an environment-friendly means of transportation according to regulation strengthening with respect to greenhouse gas emission and fuel efficiency.
Hereinafter, a method of fabricating the metal alloy composition according to an embodiment is described.
A method of fabricating the metal alloy composition may include fusing a parent alloy including at least one early transition metal (ETM), at least one late transition metal (LTM), and silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %, solidifying the melted parent alloy by rapid cooling at a temperature of less than or equal to a glass transition temperature to produce an amorphous metal alloy, and heat treating the amorphous metal alloy to form an amorphous or crystalline metal matrix and a metal particle dispersed in the metal matrix and having hyperelasticity characteristics.
The parent alloy may further include at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga), in addition to the early transition metal, the late transition metal, and silicon (Si).
In an embodiment, the elements in the parent alloy may have purity of about 90% to about 99.99% within a weight range of 10 g to 30 g.
In an embodiment, the melting process may be performed using an arc melting method. That is, in an embodiment, elements of the parent alloy may be melted using an arc melting method.
The arc melting may be, for example, performed under a highly pure argon atmosphere of about 90% to about 99.99%. However, this is merely exemplary, and melting methods using other known heat sources may also be used.
The solidifying process of the melted parent alloy may be performed using a suction casting or melt-spinning method.
The suction casting may be used to prepare an amorphous metal alloy solidified into a rod shape or a sheet shape by putting the parent alloy on a copper mold to remelt it through arc melting under a highly pure argon atmosphere, and then opening a valve switch beneath the copper mold under vacuum to instantly inject the melt solution into the copper mold. The rod shape-solidified amorphous metal alloy may have a diameter of about 2 mm and a length of about 45 mm. The sheet-shape solidified amorphous metal alloy may have a thickness of about 300 micrometers.
In another exemplary embodiment, the melt-spinning method obtains a ribbon shape-solidified amorphous metal alloy by injecting the parent alloy into a transparent quartz pipe, remelting it with high frequency inductive heat at a vacuum degree ranging from about 10 torr to about 0 torr under an argon atmosphere ranging from about 7 kPa to about 9 kPa, injecting argon gas into the quartz pipe while the quartz pipe is simultaneously dropped, and then ejecting the melt solution onto the surface of a copper roll. Herein, a cooling speed may be controlled by a rotation speed of the copper roll and an argon gas pressure of the quartz pipe, and depending on this cooling speed, a solidified amorphous metal alloy having glass-forming ability may be prepared. The ribbon shape-solidified amorphous metal alloy may have a thickness of about 20 micrometers.
On the other hand, the amorphous metal alloy solidified through the process may have an amorphous fraction of, for example, greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or even 100% (completely amorphous). In an embodiment, a solidified amorphous metal alloy satisfying the above silicon amount may be completely amorphous.
When the amorphous fraction in this solidified amorphous metal alloy is controlled within the range or into a completely amorphous state, formation of other different phases except for the austenite phase through the subsequent heat-treatment in the metal alloy composition 10 may be minimized.
On the other hand, in the heat treatment, an isothermal heat treatment may be performed with respect to the solidified amorphous metal alloy. During the isothermal heat treatment, a heat treatment time may be controlled to control a fraction ratio of a crystalline phase having hyperelasticity characteristics and an amorphous phase in the metal alloy composition.
On the other hand, before the heat treatment, a step of molding the amorphous metal alloy into a desired shape may be further included.
Accordingly, the prepared metal alloy composition 10 may have improved dimensional precision and strength as well as secure high productivity in a simpler method than the above die casting or CNC process, and in addition, may be easily surface treated.
In addition, a product formed to have a thickness of greater than or equal to about 100 micrometers by using the metal alloy composition 10 may show an excellent hyperelasticity behavior as described above.
Hereinafter, the embodiments are illustrated in more detail with reference to examples. These examples, however, are not in any sense to be interpreted as limiting the scope of the disclosure. Furthermore, what is not described in this disclosure may be sufficiently understood by those who have knowledge in this field and will not be illustrated here.
Fabrication of Sheet-Shaped Amorphous Metal Alloy According to Examples 1 to 4 and Comparative Examples 1 and 220 g of each parent alloy according to Examples 1 to 4 and Comparative Examples 1 and 2 has a composition shown in Table 1, and is prepared by melting each element having purity of 99.99% in an arc melting method under a highly pure argon (99.999%) atmosphere. In addition, a sample obtained therefrom is repeatedly melted at least 4 times, while being turned over, in order to reduce segregation of the alloy components during the arc melting. In addition, the parent alloy is prepared into a specimen by using suction casting.
For example, the parent alloy is put on a copper mold and remelted in an arc melting method under a highly pure argon atmosphere. Then, the melt solution is instantly injected into a copper mold to obtain a solidified amorphous metal alloy by opening a valve switch beneath the copper mold under vacuum.
The prepared amorphous metal alloy has a disk shape having a diameter of 30 mm and a thickness of 300 micrometers.
20 g of a parent alloy having the same composition as that of Example 1 is prepared in an arc melting method among the above methods of fabricating a sheet-shaped amorphous metal alloy by using each element having purity of 99.99% under a highly pure argon (99.999%) atmosphere. In addition, the sample is repeatedly melted at least 4 times, while being turned over in order to reduce segregation of the alloy components during the arc melting.
Subsequently, the parent alloy is inserted into a transparent quartz pipe and then remelted by high frequency inductive heat after setting a vacuum degree in a range of 10 torr to 0 torr under an argon atmosphere of 7 kPa to 9 kPa to prepare a melted metal alloy having a high amorphous fraction. Then, argon gas is simultaneously injected into the quartz pipe while the quartz pipe is sharply dropped, to eject the melt solution onto the surface of a spinning copper roll and obtain a solidified amorphous metal alloy according to Example 5.
The amorphous metal alloy of Example 5 has a composition of (Ti0.3Zr0.2Ni0.35Cu0.15)98.5Si1.5 and a ribbon shape having a thickness of 30 micrometers.
Fabrication of Rod-Shaped Amorphous Metal Alloy According to Examples 6 to 8 and Comparative Examples 3 and 420 g of a parent alloy is prepared to respectively have compositions (Example 6: (Ti0.3Zr0.2Ni0.35Cu0.15)98.7Si1.3, Example 7: (Ti0.3Zr0.2Ni0.35Cu0.15)98Si2, Example 8: (Ti0.3Zr0.2Ni0.35Cu0.15)99Si1, Comparative Example 3: Ti0.3Zr0.2Ni0.35Cu0.15, Comparative Example 4: (Ti0.3Zr0.2Ni0.35Cu0.15)98Si2 by melting elements having high purity of 99.99% under a highly pure argon (99.999%) atmosphere in an arc melting method. In addition, the parent alloy is repeatedly melted at least 4 times during the arc melting in order to reduce segregation of the alloy components while being turned over. In addition, the parent alloy is prepared into a specimen by using suction casting.
For example, the parent alloy is put on a copper mold and remelted under a highly pure argon atmosphere through arc melting, and the melt solution is gradually injected into the copper mold by opening a valve switch beneath the copper mold (Cu mold) under vacuum to prepare a solidified crystalline metal alloy.
The metal alloys according to Examples 6 to 8 and Comparative Examples 3 and 4 are respectively 100% crystallized by controlling the above cooling speed and have the same composition as the above parent alloy and a rod shape having a diameter of 2 mm.
Evaluation 1: Structure and Thermal Analysis of Amorphous Metal AlloyAn endothermic reaction may occur for movement or motion of atoms in the supercooled liquid region between the glass transition temperature (Tg) and the crystallization temperature (Tx), while an exothermic reaction may occur when crystallization proceeds above the crystallization temperature (Tx), so the sample undergoes phase transformation from an unstable amorphous phase to a stable crystalline phase, for example, to a crystalline phase having hyperelasticity characteristics.
Referring to
Referring to
The result shows a glass-forming ability parameter of a Ti—Ni-based metal alloy such as Tg, Tx, and ΔTx, may be controlled by using an additional element such as silicon (Si), tin (Sn), and/or the like.
Evaluation 2: XRD Analyses of Amorphous Metal Alloy and Crystalline Metal AlloyReferring to
Particularly, the rod-shaped crystalline metal alloy of Example 6 shows no other peaks except for the above peak and thus has a single austenite phase.
Evaluation 3: Mechanical Characteristic Analysis of Rod-Shaped Crystalline Metal AlloyFor each rod-shaped crystalline metal alloy of Examples 7 and 8 and Comparative Examples 3 and 4, points corresponding to a martensitic transformation stress (σ1), a maximum elastic recovery ability (σ2), a maximum recovery strain (@ 8%, ε2) of a product, a maximum destruction stress (σ3), and a maximum destruction strain (ε3) are separately selected and shown in Table 2.
The maximum destruction stress denotes a stress that ultimately destroys a material, and the maximum destruction strain denotes a strain at the maximum destruction stress.
First, referring to Table 2, the rod-shaped crystalline metal alloy including 2 atomic % of silicon (Si) according to Comparative Example 4 shows no hyperelasticity behavior, unlike those of Examples 7 and 8 and Comparative Example 3.
On the other hand, referring to
While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims
1. A metal alloy composition comprising:
- an amorphous or crystalline metal matrix; and
- a metal particle having hyperelasticity by phase transition dispersed in the metal matrix,
- wherein the metal alloy composition includes at least one early transition metal (ETM),
- at least one late transition metal (LTM), and
- silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %.
2. The metal alloy composition of claim 1, wherein a supercooling liquid region of the metal alloy composition is about 40 K to about 100 K.
3. The metal alloy composition of claim 1, wherein the early transition metal is selected from titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), hafnium (Hf), molybdenum (Mo), tantalum (Ta), chromium (Cr), yttrium (Y), and tungsten (W).
4. The metal alloy composition of claim 1, wherein the late transition metal is selected from nickel (Ni), iron (Fe), copper (Cu), cobalt (Co), copper (Cu), and manganese (Mn).
5. The metal alloy composition of claim 1, wherein a ratio of an atomic number of the late transition metal relative to a sum of atomic numbers of the early transition metal and the late transition metal is about 0.4 to about 0.6.
6. The metal alloy composition of claim 1, wherein the metal alloy composition is represented by Chemical Formula 1:
- (TixZr1-xNiyCu1-y)100-a-bSiaAb [Chemical Formula 1]
- wherein, in Chemical Formula 1,
- A is at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga),
- 0.25≤x≤0.45, 0.3≤y≤0.5, 0<a<2, and 0≤b≤2.
7. The metal alloy composition of claim 1, wherein a martensitic transformation stress of the metal particle is about 1000 MPa to about 2300 MPa.
8. The metal alloy composition of claim 1, wherein a maximum recovery stress of the metal particle is about 1500 MPa to about 2500 MPa.
9. The metal alloy composition of claim 1, wherein a maximum recovery strain of the metal particle measured under an 8% strain condition ranges from about 5% to about 8%.
10. The metal alloy composition of claim 1, wherein the metal particle has an austenite phase at about 0° C. to about 50° C.
11. The metal alloy composition of claim 10, wherein the austenite phase is transited into one phase of a B19 phase, an R phase, and a B19′ phase by stress application.
12. The metal alloy composition of claim 10, wherein the austenite phase is transited into a B19′ phase by stress application, and may be recovered to the austenite phase by removal of the applied stress.
13. The metal alloy composition of claim 1, wherein
- a temperature corresponding to a crossing point of the metal particle between a plastic deformation critical stress curve and a martensite phase induction critical stress curve depending on temperature changes is greater than about 50° C., and
- the martensite transformation starting temperature, martensite transformation finishing temperature, austenite transformation starting temperature, and austenite transformation finishing temperature is less than about 0° C.
14. A product composed of the metal alloy composition of claim 1.
15. The product of claim 14, wherein a thickness of the product is greater than or equal to about 100 micrometers.
16. A method of fabricating the metal alloy composition, comprising:
- fusing a parent alloy including at least one early transition metal (ETM), at least one late transition metal (LTM), and silicon (Si) in an amount of greater than about 0 atomic % and less than about 2 atomic %;
- solidifying the melted parent alloy at a supercooling liquid region between a glass transition temperature and a crystallization temperature to produce an amorphous metal alloy; and
- heat treating the amorphous metal alloy to form an amorphous or crystalline metal matrix and a metal particle dispersed in the metal matrix and having hyperelasticity characteristics.
17. The method of claim 16, wherein, while producing the amorphous metal alloy, an amorphous fraction of the produced amorphous metal alloy is greater than or equal to about 70 volume %.
18. The method of claim 17, wherein an amorphous fraction of the produced amorphous metal alloy is about 100 volume %.
19. The method of claim 16, wherein, while fusing the parent alloy, elements of the parent alloy are melted using an arc melting method.
20. The method of claim 16, wherein the parent alloy further includes at least one selected from boron (B), phosphorus (P), indium (In), lanthanum (La), aluminum (Al), silver (Ag), tin (Sn), germanium (Ge), and gallium (Ga).
21. The method of claim 16, wherein, before heat treating the amorphous metal alloy, the produced amorphous metal alloy is further molded into a predetermined shape.
Type: Application
Filed: Mar 29, 2018
Publication Date: Oct 4, 2018
Inventors: Dohyang KIM (Seoul), Minyoung NA (Gwangju-si), Jeongsoo KIM (Daegu-si), Woochul KIM (Seoul), Yeongseong KIM (Seoul), Wontae KIM (Seoul)
Application Number: 15/940,210
