Method for Making a Strong Aluminum Alloy

Abstract

A method is used to make an aluminum alloy with excellent tensile strength, low density and excellent radiation. The method includes the steps of providing a base material, adding 0.06 wt % to 0.30 wt % of zirconium and 0.06 wt % to 0.30 wt % of vanadium to the base material, and melting the basic material with the zirconium and vanadium to provide an aluminum alloy. The base material includes 92.55 wt % to 97.38 wt % of aluminum, 0.9 wt % to 1.8 wt % of silicon, less than 0.5 wt % of iron, 0.6 wt % to 1.2 wt % of copper, 0.4 wt % to 1.1 wt % of manganese, 0.6 wt % to 1.4 wt % of magnesium, less than 0.40 wt % of chromium, less than 0.25 wt % of zinc and less than 0.20 wt % of titanium.

Description

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a method for making a strong aluminum alloy and, more particularly, to a method for providing an aluminum alloy with excellent tensile strength, hardness and radiation and low density.

2. Related Prior Art

Al—Si—Mg (6000 series) alloys have been used in the defense industry, automobile industry and sports industry for being light weight. Al—Si—Mg alloys however exhibit inadequate strength and need improvement.

To improve the strength of commercially available Al—Si—Mg alloys, they may be added with Sc as a grain refiner. The concentration of the Sc is about 0.03% to 0.20% to increase the tensile strength and hardness of the Al—Si—Mg alloys to about 450 MPa.

Sc is rare and therefore expensive. Accordingly, the Al—Si—Mg alloys added with the Sc are expensive.

The present invention is therefore intended to obviate or at least alleviate the problems encountered in conventional alloy.

SUMMARY OF INVENTION

It is the primary objective of the present invention to provide a method for making an aluminum alloy with excellent tensile strength, low density and excellent radiation.

To achieve the foregoing objective, the method includes the steps of providing a base material, adding 0.06 wt % to 0.30 wt % of zirconium and 0.06 wt % to 0.30 wt % of vanadium to the base material, and melting the basic material with the zirconium and vanadium to provide an aluminum alloy.

The base material includes 92.55 wt % to 97.38 wt % of aluminum, 0.9 wt % to 1.8 wt % of silicon, less than 0.5 wt % of iron, 0.6 wt % to 1.2 wt % of copper, 0.4 wt % to 1.1 wt % of manganese, 0.6 wt % to 1.4 wt % of magnesium, less than 0.40 wt % of chromium, less than 0.25 wt % of zinc and less than 0.20 wt % of titanium.

In another aspect, the step of melting the base material with the zirconium and vanadium includes the step of providing an induction furnace for melting the base material with the zirconium and vanadium in argon.

In another aspect, the method further includes the steps of degassing and slag-removing the aluminum alloy melt, turning the aluminum alloy melt into an aluminum alloy nugget by direct chill casting, and pressurizing the aluminum alloy nugget to turn the aluminum alloy nugget into another shape.

In another aspect, the step of pressurizing the aluminum alloy nugget includes the step of extruding the aluminum alloy nugget. The step of extruding the aluminum alloy nugget may include the step of providing an extruding machine.

In another aspect, the step of pressurizing the aluminum alloy nugget includes the step of providing a rolling machine for rolling the aluminum alloy nugget. The step of rolling the aluminum alloy nugget may include the step of providing a rolling machine.

Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described via detailed illustration of the preferred embodiment referring to the drawings wherein:

FIG. 1 is a flow chart of a method for providing an aluminum alloy with excellent tensile strength, hardness and radiation and low density according to the preferred embodiment of the present invention;

FIG. 2 is a table of compositions of alloys made by the method shown in FIG. 1 and a conventional alloy;

FIG. 3 is a table of several mechanical properties of the alloys shown in FIG. 2 after extruding; and

FIG. 4 is a table of several mechanical properties of the alloys shown in FIG. 2 after T6 heat treatment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a method for providing an aluminum alloy with excellent mechanical properties. The excellent mechanical properties include tensile strength, hardness and radiation and low density.

At first, there is provided a base material 10. The base material 10 includes 92.55 wt % to 97.38 wt % of aluminum 101, 0.9 wt % to 1.8 wt % of silicon 102, 0.5 wt % of iron 103, 0.6 wt % to 1.2 wt % of copper 104, 0.4 wt % to 1.1 wt % of manganese 105, 0.6 wt % to 1.4 wt % of magnesium 106, less than 0.4 wt % of chromium 107, less than 0.25 wt % of zinc 108 and less than 0.20 wt % of titanium 109. Then, the basic material 10 is added with zirconium 111 and vanadium 112, and molten in argon in an induction furnace, thus providing aluminum alloy melt 11.

Secondly, the aluminum alloy melt 11 is subjected to degassing and slag-removing before it is subjected to extruding b in the form of chill casting to provide an aluminum alloy nugget 12.

Thirdly, the aluminum alloy nugget 12 is subjected to pressurizing c, thus providing an aluminum alloy product 1. The aluminum alloy nugget 12 is made into the aluminum alloy product 1 by extruding or rolling. For example, the aluminum alloy nugget 12 may be made into the aluminum alloy product 1 in the form of a rod or plank with an extruding machine. Alternatively, the aluminum alloy nugget 12 may be made into the aluminum alloy product 1 in the form of a board or sheet with a rolling machine.

Referring to FIG. 2, aluminum 101, silicon 102, magnesium 106, copper 104, manganese 105, zirconium 111 and scandium may be used to provide a first specimen. Aluminum 101, silicon 102, magnesium 106, copper 104, manganese 105, zirconium 111 and vanadium 112 may be used to provide second and third specimens. Aluminum 101, silicon 102, magnesium 106, copper 104 and manganese 105 may be used to provide a conventional alloy.

Referring to FIGS. 3 and 4, the first specimen, which is added with scandium, is made with a tensile strength of 240 MPa and a percentage elongation of 19.4%. The second and third specimens, which are added with zirconium 111 and vanadium 112, are respectively made with tensile strengths of 212 MPa and 225 MPa and percentage elongations of 18.5% and 17.9%.

After T6 heat treatment, the tensile strength of the first specimen, which is added with scandium, is increased to 478 MPa, and the percentage elongation is reduced to 11.5%. The fourth specimen, which is added with zirconium 111 and vanadium 112, is made with a tensile strength of 202 MPa and a percentage elongation of 19.5%. After the T6 heat treatment, the tensile strengths of the second and third specimens, which are added with zirconium 111 and vanadium 112, are respectively increased to 455 MPa and 475 MPa, and the percentage elongations are reduced to 13.1% and 12.5%. It is learned that the tensile strengths of the alloys 1 and 3 are similar to one another after the T6 treatment. The second specimen exhibits the best percentage elongation. The second specimen exhibits a lower tensile strength than the first and third specimens for including less manganese 105, a strength phase. After the T6 heat treatment, the tensile strength of the fourth specimen, which is added with zirconium 111 and vanadium 112, is increased to 400 MPa, and the percentage elongation is reduced to 14.7%.

The grain-refining of aluminum alloys is mainly done by addition of grain refiners such as scandium (“Sc”) and zirconium 111 (“Zr”) to grow precipitates such as Al₃Sc at grain boundaries to interfere with the growth of the grains. Alternatively, a strengthening phase may be distributed in the grains. When the grains are refined and strengthened, the grain boundaries are effective obstacles against slip, concentration of stress in front of the grain boundaries activate a lot of slip systems, and deformation of the alloys become even. Thus, the strength and tenacity of the alloys are increased. The relation of the yield strengths of the alloys to the sizes of the grains can be expressed in a Hall-Petch equation, i.e., σ_yield=σ₀+kd^−1/2, wherein σ₀ stands for the yield strength of a single grain, k stands for a slope in the Hall-Petch equation, and d stands for the size of the grain.

The T6 heat treatment of Al alloy is a well-known technique of the 6000 series, which is the artificial aging after the solution treatment. In the solution treatment, the material is heated above the solution line to become a single solution phase; and, then, is quenched at a high temperature. Thus, the single solution phase is quickly cooled down to get an oversaturated solution. In the artificial aging, the oversaturated solution is put in a furnace with a certain temperature kept for gradually precipitating precipitate with changed characteristics. For example, in one preferred embodiment, the heat treatment of Al alloy in the present invention is as follows: a solution treatment at 530° C. with the temperature kept for 1 hour; a quenching at 25° C., which is a water quenching; and an artificial aging at 177° C. with the temperature kept for 8 hours.

Based on the 6066-T6 alloy, the present invention preferably adds small amounts of V and Zr with a ratio of Si/Mg between 1.2 and 1.5 to form a strengthening phase of Mg₅Si₄. In a preferred embodiment, the T6 of the present invention has a tensile strength of 475 MPa and a yield strength of 417 MPa, which is better than the tensile strength of the prior art.

Applicant notes that the recited prior art typically includes expensive rare earth elements, while Applicant's recited composition preferably avoids the costly rare earth elements. Applicant further notes that the recited invention is based on 6066-T6 alloy melted with a particular amount of V and Zr. In one preferred embodiment, the anti-stretching strength of the alloy after T6 is 475 MPa, the yield strength is 417 MPa and the extensibility is 12.5%. All these are clearly better than those of conventional 6066-T6, which are 395 MPa of anti-stretching strength, 359 MPa of yield strength and 12% of extensibility. In addition, the mechanical characteristics exceed those of the mechanical characteristics of the conventional 6066-T6 alloy modified with addition of expensive Sc in alloy. Thus, the recited invention not only has better mechanical characteristics than traditional 6066 alloy, but also has a reduced cost of alloy.

Further, the present invention improves the mechanical strength of the Al—Si—Mg alloy for broadening the application fields of the device. Without adding the rare earth metal Sc, the present invention adds small amounts of Zr and V as grain refiners to strengthen the tensility of the alloy to, in a preferred embodiment, about 450 MPa or, in another preferred embodiment, 400 MPa.

The method of the present invention provides aluminum alloys without the drawbacks of the prior art. For example, the aluminum alloys of the present invention exhibit high tensile strengths, excellent plastic deformations, low densities, radiations and hardness. Hence, the aluminum alloys of the present invention can be used in shells in the defense industry, the aerospace industry, the automobile industry, the appliance industry and the OA industry for example.

The present invention has been described via the detailed illustration of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.

Claims

1. A method for making a strong aluminum alloy including the steps of providing a base material consisting essentially of 92.55% to 97.38% of aluminum, 0.9% to 1.8% of silicon, less than 0.5% of iron, 0.6% to 1.2% of copper, 0.4% to 1.1% of manganese, 0.6% to 1.4% of magnesium, less than 0.40% of chromium, less than 0.25% of zinc and less than 0.20% of titanium; adding 0.06% to 0.16% of zirconium and 0.06% to 0.30% of vanadium to the base material, the above all percentages being by weight, and melting the basic material with the zirconium and vanadium to provide an aluminum alloy having a strength of 400 Mpa after a T6 heat treatment.

2. The method for making a strong aluminum alloy according to claim 1, wherein the step of melting the base material with the zirconium and vanadium includes the step of providing an induction furnace for melting the base material with the zirconium and vanadium in argon to provide an aluminum alloy melt.

3. The method for making a strong aluminum alloy according to claim 2, further including the steps of subjecting the aluminum alloy melt to degassing and slag-removing; turning the aluminum alloy melt into an aluminum alloy nugget by direct chill casting; and

pressurizing the aluminum alloy nugget to turn the aluminum alloy nugget into another shape.

4. The method for making a strong aluminum alloy according to claim 3, wherein the step of pressurizing the aluminum alloy nugget includes the step of extruding the aluminum alloy nugget.

5. The method for making a strong aluminum alloy according to claim 4, wherein the step of extruding the aluminum alloy nugget includes the step of providing an extruding machine.

6. The method for making a strong aluminum alloy according to claim 3, wherein the step of pressurizing the aluminum alloy nugget includes the step of providing a rolling machine for rolling the aluminum alloy nugget.

7. The method for making a strong aluminum alloy according to claim 6, wherein the step of rolling the aluminum alloy nugget includes the step of providing a rolling machine.