HYPER-EUTECTIC ALLOY WITH IMPROVED ELONGATION AND IMPACT STRENGTH

Info

Publication number: 20200190633
Type: Application
Filed: Jun 18, 2019
Publication Date: Jun 18, 2020
Applicants: HYUNDAI MOTOR COMPANY (Seoul), KIA MOTORS CORPORATION (Seoul)
Inventor: A-Reum Kwon (Gunpo-si)
Application Number: 16/444,919

Abstract

A composition of a hyper-eutectic alloy related to the production of an intermolecular compound phase and primary Si. The hyper-eutectic alloy includes 1.0 to 3.0 wt % of copper (Cu), 0.1 to 0.3 wt % of magnesium (Mg), 13.5 to 15.5 wt % of silicon (Si), 0.1 wt % or less of nickel (Ni), and a balance of aluminum (Al). Thus, it is possible to have improved abrasion resistance as compared to ADC12 alloy and to have improved elongation and impact resistance as compared to K14 alloy.

Description

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2018-0160172, filed on Dec. 12, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates to a composition of a hyper-eutectic alloy, and more particularly, to a composition related to the production of an intermolecular compound phase and primary Si.

2. Description of the Related Art

Currently, ADC12 alloy and K14 alloy, which are commercially available aluminum alloys, have a problem in that it is difficult to apply those alloys to thin-walled transmission parts requiring abrasion resistance and elongation. The reason is because, in the case of ADC12 alloy, which is an eutectic alloy, abrasion resistance is poor. As a result, the wear occurring phenomenon due to an opponent steel part is obvious when the alloy is applied to thin-walled clutch parts of a transmission. In the case of K14 alloy, which is a hyper-eutectic alloy having excellent abrasion resistance, elongation and breakage strength are reduced by primary Si, which serves as an abrasion resistant particle. Furthermore, there have been various attempts to enhance abrasion resistance characteristics of ADC12 alloy, for example, such as by shot peening or heat treatment, but there is a problem in that these attempts are not effective for improving abrasion resistance characteristics.

SUMMARY

An object of the present disclosure is to simultaneously improve elongation and impact resistance in an alloy as compared to K14 alloy while improving abrasion resistance as compared to ADC12 alloy.

To achieve the object, the present disclosure provides a hyper-eutectic alloy including 1.0 to 3.0 wt % of copper (Cu), 0.1 to 0.3 wt % of magnesium (Mg), 13.5 to 15.5 wt % of silicon (Si), 0.1 wt % or less of nickel (Ni), and a balance of aluminum (Al).

In one embodiment, the hyper-eutectic alloy may further include 0.5 wt % or less of iron (Fe).

In one embodiment, the hyper-eutectic alloy may further include 0.1 wt % or less of manganese (Mn).

In one embodiment, the hyper-eutectic alloy may further include 0.1 wt % or less of zinc (Zn).

In one embodiment, primary Si particles may have an average size of 30 um or less.

According to the present disclosure, it is possible in an alloy to have improved abrasion resistance as compared to ADC12 alloy and to have improved elongation and impact resistance as compared to K14 alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate intermetallic compound phases in Examples 1 and 2, respectively, of the present disclosure.

FIGS. 2A and 2B illustrate intermetallic compound phases in Comparative Examples 1 and 2, respectively, of the present disclosure.

FIG. 3 illustrates an intermetallic compound phase in Comparative Example 3 of the present disclosure.

FIG. 4A is a photograph of an intermetallic compound phase of a hyper-eutectic alloy including 2.5 wt % of copper (Cu) as an example of the present disclosure.

FIG. 4B is a photograph of an intermetallic compound phase of a hyper-eutectic alloy including 3.5 wt % of copper (Cu) as a comparative example of the present disclosure.

FIGS. 5A-5D are photographs illustrating the sizes of primary Si according to the content of magnesium (Mg), and in FIGS. 4A and 4B, 0.2 wt %, 0.3 wt %, 0.5 wt %, and 0.8 wt % of magnesium (Mg) are included, respectively.

FIG. 6 illustrates average particle sizes of primary Si according to the content of magnesium (Mg).

FIG. 7A is a photograph of the structure when the content of silicon (Si) is more than 15.5 wt %.

FIG. 7B is a photograph of the structure when the content of silicon (Si) is less than 13.5 wt %.

FIG. 8 illustrates breakage strengths of Conditions 1 to 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present disclosure are described in detail. However, the present disclosure is not limited or restricted by the disclosed embodiments. Objects and effects of the present disclosure will be naturally understood or become apparent from the following description, and the objects and effects of the present disclosure are not limited by only the following description. Further, in the description of the present disclosure, when it is determined that the detailed description for the publicly known technology related to the present disclosure can unnecessarily obscure the gist of the present disclosure, the detailed description thereof has been omitted.

TABLE 1 Classification Cu Mg Si Fe Mn Zn Ni Al Present 1.0~3.0 0.1~0.3 13.5~15.5 max. max. max. max. Rem. disclosure 0.5 0.1 0.1 0.1 Eutectic 1.5~3.5 max. 9.6~12.0 max. max. max. — Rem. alloy 0.30 1.3 0.5 1.0 (ADC12) Hyper- 4.0~5.0 max. 13.5~15.5 max. max. max. max. Rem. eutectic 0.5 1.3 0.5 0.1 0.5 alloy (K14)

Table 1 shows the main compositions of the hyper-eutectic alloy according to the present disclosure (hereinafter, referred to as ‘present hyper-eutectic alloy’), ADC12 alloy, which is an eutectic alloy, and K14 alloy, which is a hyper-eutectic alloy. Referring to Table 1, the present hyper-eutectic alloy includes 1.0 to 3.0 wt % of copper (Cu), 0.1 to 0.3 wt % of magnesium (Mg), 13.5 to 15.5 wt % of silicon (Si), 0.1 wt % or less of nickel (Ni), and a balance of aluminum (Al). Furthermore, the present hyper-eutectic alloy may further include 0.5 wt % or less of iron (Fe), 0.1 wt % or less of manganese (Mn), and 0.1 wt % or less of zinc (Zn).

The characteristics of the present hyper-eutectic alloy are to include copper (Cu) in a smaller amount than the content of copper (Cu) in the eutectic alloy (ADC12) and the hyper-eutectic alloy (K14), the smaller amount being 1.0 to 3.0 wt % of copper (Cu), and to set the content of magnesium (Mg) to 0.1 to 0.3 wt % unlike the eutectic alloy (ADC12) and the hyper-eutectic alloy (K14).

Copper (Cu) serves to increase the strength of the alloy by forming an Al—Cu-based intermetallic compound during aluminum molten metal solidification. However, when the content of copper (Cu) in the alloy is high, an Al₂Cu phase is produced and magnesium (Ma) forms an Al₅Cu₂Mg₈Si₆phase and the phase is consumed, so that a β-Al₅FeSi phase is produced. This needle-like β-Al₅FeSi phase causes a remarkable decrease in elongation. In contrast, when the content of copper (Cu) is low, a small amount of Al₅Cu₂Mg₈Si₆phase is formed due to a small content of copper (Cu), and Al₈Mg₃FeSi₆is crystallized rather than the β-Al₅FeSi phase by the residual magnesium (Mg). Simultaneously, a relatively small amount of needle-like β-Al₅FeSi phase is formed, thereby improving the elongation.

In summary, the present hyper-eutectic alloy intends to improve low elongation characteristics of the hyper-eutectic alloy in the related art by limiting the content of copper (Cu) to 1.0 to 3.0 wt %, considering that primary Si particles and a plurality of intermetallic compounds are present in the hyper-eutectic alloy in the related art, and thus, the elongation deteriorates.

Magnesium (Mg) serves to control the sizes of primary Si particles, which affect the elongation. When the content of magnesium (Mg) is less than 0.1 wt % or more than 0.3 wt %, an average size of primary Si particles may be more than 30 um, and thus, the elongation may deteriorate. Accordingly, in one embodiment, in order to control the average size of primary Si particles to 30 um or less, 0.1 to 0.3 wt % of magnesium (Mg) is added.

Silicon (Si) serves to precipitate primary Si within a range of the eutectic point or more and allows the primary Si to enhance abrasion resistance as an abrasion resistant particle. When the content of silicon (Si) in the alloy is less than 13.5 wt %, primary Si is not precipitated. When the content is more than 15.5 wt %, plate-like primary Si is crystallized in a large amount. As a result, brittleness is increased. Accordingly, in one embodiment, 13.5 to 15.5 wt % of silicon (Si) is added.

Iron (Fe) serves to prevent die soldering during casting. When iron (Fe) is added in an amount of more than 0.5 wt %, a plurality of β-Al₅FeSi phases is produced. As a result, the elongation deteriorates. Thus, in one embodiment, 0.5 wt % or less of iron (Fe) is added.

Manganese (Mn) serves to enhance the elongation by suppressing iron (Fe) from producing needle-like β-Al₅FeSi due to the formation of the Al₁₅(Mn,Fe)Si₂phase. When manganese (Mn) is added in an amount of more than 0.1 wt %, an intermetallic compound such as Al₂₀Mn₃Cu₂is produced. As a result, the elongation deteriorates. Thus, in one embodiment, 0.1 wt % or less of manganese (Mn) is added.

Zinc (Zn) is highly solid solutionized in aluminum (Al), and thus serves to improve the mechanical properties through solid-solution strengthening. When zinc (Zn) is added in an amount of more than 0.1 wt %, the elongation may deteriorate. Thus, in one embodiment, 0.1 wt % or less of zinc (Zn) is added.

Nickel (Ni) serves to enhance heat resistance and abrasion resistance. When nickel (Ni) is added in an amount of more than 0.1 wt %, the elongation may deteriorate as the Al₃Ni₂and Al₇Cu₄Ni phases are produced. Thus, in one embodiment, 0.1 wt % or less of nickel (Ni) is added.

TABLE 2 Classification Cu Mg Si Fe Mn Zn Ni Example 1 1.19 0.28 14.02 0.022 0.008 0.006 0.013 Example 2 2.51 0.29 14.01 0.024 0.009 0.003 0.014 Comparative 3.23 0.26 13.75 0.021 0.008 0.004 0.012 Example 1 Comparative 4.16 0.22 13.77 0.023 0.012 0.003 0.014 Example 2 Comparative 2.50 0.21 13.78 0.023 0.012 0.003 0.31 Example 3 Comparative 2.40 0.23 14.21 0.78 0.012 0.002 0.014 Example 4 Comparative 2.69 0.66 13.65 0.021 0.009 0.005 0.013 Example 5 Comparative 2.54 0.20 15.68 0.023 0.008 0.003 0.014 Example 6 Comparative 2.11 0.23 10.55 0.89 0.18 0.74 — Example 7

Table 2 shows the compositions of Examples 1 and 2 and Comparative Examples 1 to 7 of the present disclosure. Referring to Table 2, Comparative Examples 1 and 2 include 3.23 wt % and 4.16 wt % of copper (Cu), which are more than the highest content of copper (Cu) of the present disclosure. Comparative Example 3 includes 0.31 wt % of nickel, which is more than the highest content of nickel (Ni) of the present disclosure. Comparative Example 4 includes more than the highest content of iron (Fe). Comparative Example 5 includes more than the highest content of magnesium (Mg). Comparative Example 6 includes more than the highest content of silicon (Si). The composition in Comparative Example 7 is included in the composition of the eutectic alloy ADC12 alloy in Table 1.

TABLE 3 Tensile Yield Impact Wear strength strength Elongation strength amount Classification (MPa) (MPa) (%) (J/cm²) (g) Example 1 249 216 1.13 1.34 0.0093 Example 2 275 234 1.24 1.19 0.008 Comparative 280 242 0.96 0.90 0.0085 Example 1 Comparative 277 254 0.77 0.85 0.0075 Example 2 Comparative 291 262 0.54 0.92 0.008 Example 3 Comparative 299 247 0.96 0.87 0.006 Example 4 Comparative 260 251 0.58 0.78 0.0081 Example 5 Comparative 281 271 0.61 0.74 0.003 Example 6 Comparative 265 225 1.03 1.17 0.057 Example 7

Table 3 shows the tensile strength, yield strength, elongation, impact strength, and wear amount in Examples 1 and 2 and Comparative Examples 1 to 7 of the present disclosure. The tensile strength, yield strength, and elongation were measured under the condition of 1 mm/min in accordance with ASTM E8M. For the evaluation of abrasion resistance, the reciprocating friction wear test was measured under the conditions of a conditional load of 500 N, a temperature of 150° C., a frequency of 2.5 Hz, and a time of 2,000 s by selecting a counterpart material (SCr420HB, carburization). The IZOD impact strength was measured in accordance with ASTM E23.

Referring to Table 3, it can be seen that the elongation and impact strength in Examples 1 and 2 are better than those in Comparative Examples 1 to 6 and are at a level equivalent to or more than the elongation and impact strength in Comparative Example 7 having the composition of the eutectic alloy. The wear resistance in Examples 1 and 2 is much better than that in Comparative Example 7.

FIGS. 1A and 1B illustrate intermetallic compound phases in Examples 1 and 2 of the present disclosure. Referring to FIGS. 1A and 1B, in Examples 1 and 2, primary Si (1), eutectic Si (2), Al₈Mg₃FeSi₆(3), Mg₂Si (4), and Al₅Cu₂Mg₈Si₆(5) were observed, but the β-Al₅FeSi (4′) phase was not observed. From this result, it can be seen that, when the content of copper (Cu) is 3 wt % or less, the crystallization of the β-Al₅FeSi phase is remarkably reduced. As a result, the elongation and impact strength are increased.

In contrast, it can be seen that the elongation and impact strength in Comparative Examples 1 and 2 are less than the elongation and impact strength in Examples 1 and 2. FIGS. 2A and 2B illustrate intermetallic compound phases in Comparative Examples 1 and 2 of the present disclosure. Referring to FIGS. 2A and 2B, not only primary Si (1), eutectic Si (2), Al₂Cu (3′), and Al₅Cu₂Mg₈Si₆(5), but also β-Al₅FeSi (4′) were observed. From this result, it can be seen that, when the content of copper (Cu) is more than 3 wt %, the β-Al₅FeSi phase is crystallized. As a result, the elongation and impact strength are decreased.

Comparative Example 3 is a comparative example for evaluating the effectiveness of the content of nickel (Ni) to be added to a commercially available hyper-eutectic alloy. FIG. 3 illustrates an intermetallic compound phase in Comparative Example 3 of the present disclosure. Referring to the elongation in Comparative Example 3 of FIG. 3 and Table 3, it can be seen that the Al₃Ni₂(6) and Al₇Cu₄Ni (7) phases were observed. Thus, the elongation significantly deteriorated.

Comparative Example 4 is a comparative example for evaluating elongation deterioration characteristics according to the content of iron (Fe). It can be seen that, when the content of iron (Fe) is more than 0.5 wt %, the elongation deteriorates as compared to Example 2 as a plurality of the β-Al₅FeSi phases is produced.

Comparative Example 5 is a comparative example for evaluating elongation deterioration characteristics according to the content of magnesium (Mg). It can be seen that, when the content of magnesium is more than 0.3 wt %, particle sizes of primary Si are increased more than 30 um. As a result, the elongation deteriorates.

In the cases of Comparative Example 6, it can be seen that as the content of silicon (Si) is increased, the amount of primary Si is also increased, and as a result, the elongation deteriorates. In the case of Comparative Example 7, it can be seen that primary Si serving as an abrasion resistant particle is not crystallized. As a result, the abrasion resistance significantly deteriorates.

FIG. 4A is a photograph of an intermetallic compound phase of an alloy including 2.5 wt % of copper (Cu) as an example of the present disclosure. FIG. 4B is a photograph of an intermetallic compound phase of an alloy including 3.5 wt % of copper (Cu) as a comparative example of the present disclosure. Referring to FIGS. 4A and 4B) it can be confirmed once again that it was determined whether the β-Al₅FeSi (4′) phase is crystallized according to whether the content of copper (Cu) is more than 3 wt %.

FIGS. 5A-5D are photographs illustrating the sizes of primary Si according to the content of magnesium (Mg). In FIGS. 5A-5D, 0.2 wt %, 0.3 wt %, 0.5 wt %, and 0.8 wt % of magnesium (Mg) are included, respectively. FIG. 6 illustrates average particle sizes of primary Si according to the content of magnesium (Mg).

Referring to FIGS. 5A-5D and 6, it can be confirmed that, as the content of magnesium (Mg) is increased, the particle size of primary Si is increased. It can also be seen that, when the content of magnesium (Mg) is more than 0.3 wt %, the average size of the primary Si particles is more than 30 um. In contrast, it can be seen that, when the content of magnesium (Mg) is decreased to less than 0.1 wt %, the average size of the primary Si particles is increased and the average size may be more than 30 um.

FIG. 7A is a photograph of the structure when the content of silicon (Si) is more than 15.5 wt % and FIG. 7B is a photograph of the structure when the content of silicon (Si) is less than 13.5 wt %. Referring to FIGS. 7A and 7B, it can be confirmed that the elongation and impact strength in Comparative Examples 6 and 7 in Table 3 are correlated with large amount of crystallization and non-crystallization of primary Si.

TABLE 4 ADC14 K14 ADC12-T5 Classification alloy alloy alloy Present disclosure Elongation (%) 0.61 0.74 1.03 1.24 Impact strength 0.68 0.87 1.17 1.34 (J/cm²) Torsional 292 307 417 401 breaking (Evaluation of strength torsional fatigue (kgf · m) strength satisfies 1,000,000 cycles) Wear amount (g) 0.003 0.004 0.057 0.008

TABLE 5 Classification Condition-1 Condition-2 Condition-3 Condition-4 Condition-5 Condition Outer Ψ146.7 Ψ147.16 Ψ147.76 Ψ148.36 Ψ148.96 of changing diameter outer diameter Condition Total wall 2.17 2.4 2.7 3.0 3.3 of changing thickness tooth Amount of 0.0 +0.23 +0.53 +0.83 +1.13 thickness thickness increased Breakage Average 305.4 331.2 385.3 402.4 411 strength Minimum 266.9 299.1 351.5 376 354.1 (kgf · m) value

Table 4 is a table comparing and summarizing the elongations, impact strengths, torsional breaking strengths, and wear amounts of ADC14 alloy and K14 alloy, which are hyper-eutectic alloys, ADC12-T5 alloy, which is an eutectic alloy, and the present hyper-eutectic alloy. Table 5 is a table summarizing average breakage strengths and minimum breakage strengths of Condition-1 to Condition-5 in which the thickness of the existing commercially available hyper-eutectic alloy is varied. FIG. 8 illustrates breakage strengths of Condition-1 to Condition-5.

The existing commercially available eutectic alloy, such as ADC12 alloy, has insufficient abrasion resistance, and thus additionally requires a surface treatment process for securing abrasion resistance when applied to parts requiring abrasion resistance. But abrasion resistance is insufficiently secured even when the surface treatment process is used, so that an existing commercially available hyper-eutectic alloy including abrasion resistance is also applied. However, when parts are manufactured and evaluated by applying the existing commercially available hyper-eutectic alloy, the elongation and impact strength are insufficient as compared to ADC12 alloy, so that it can be confirmed that the torsional breaking strength is remarkably decreased, and 310 kgf·m cannot be satisfied. In order to complement the disadvantage, the disadvantage may be solved by increasing the thickness of a product. In this case, it can be experimentally confirmed that the deterioration in breakage strength may be alleviated only when the existing thickness is increased by minimally 40% or more.

In this case, due to an increase in weight accompanied by the increase in thickness of the part, the weight reduction effect according to the use of an aluminum material is reduced. However, when the present hyper-eutectic alloy is applied, it is possible to secure elongation and impact strength at a level equivalent to or more than those of ADC12 alloy. Thus, it is possible to secure the torsional breaking strength of a product, which is equivalent to or more than that of ADC12 alloy, and it is possible to secure abrasion resistance at a level equivalent to that of the existing commercially available hyper-eutectic alloy. Accordingly, it can be seen that it is possible to directly apply the present hyper-eutectic alloy to existing parts without an additional increase in thickness and a modification of the shape as in the existing commercially available hyper-eutectic alloy. The fatigue life of a part may be satisfied by evaluating the torsional fatigue strength of the part.

Aspects of the present disclosure have been described in detail through representative Examples. However, it is to be understood by a person with ordinary skill in the art to which the present disclosure pertains that various modifications are possible in the above-described Examples within the range not departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the above-described Examples but should be determined by, not only the claims to be described below, but also all the changes or modified forms derived from the claims and the equivalent concepts thereof.

Claims

1. A hyper-eutectic alloy with improved elongation and impact strength, the hyper-eutectic alloy comprising 1.0 to 3.0 wt % of copper (Cu), 0.1 to 0.3 wt % of magnesium (Mg), 13.5 to 15.5 wt % of silicon (Si), 0.1 wt % or less of nickel (Ni), and a balance of aluminum (Al).

2. The hyper-eutectic alloy of claim 1, further comprising 0.5 wt % or less of iron (Fe).

3. The hyper-eutectic alloy of claim 1, further comprising 0.1 wt % or less of manganese (Mn).

4. The hyper-eutectic alloy of claim 1, further comprising 0.1 wt % or less of zinc (Zn).

5. The hyper-eutectic alloy of claim 1, wherein primary Si particles have an average size of 30 um or less.

6. The hyper-eutectic alloy of claim 1, wherein an elongation of the alloy is higher than that of K14 alloy.

7. The hyper-eutectic alloy of claim 6, wherein the elongation of the alloy is 1.13 to 1.24%.

8. The hyper-eutectic alloy of claim 1, wherein a wear amount of the alloy is lower than that of ADC12 alloy.

9. The hyper-eutectic alloy of claim 8, wherein the wear amount of the alloy is 0.008 to 0.0093 g.

10. The hyper-eutectic alloy of claim 1, wherein a torsional breaking strength of the alloy is higher than that of K14 alloy.

11. The hyper-eutectic alloy of claim 1, wherein an impact strength of the hyper-eutectic alloy is higher than that of ADC14, K14 and ADC12 alloys.

12. The hyper-eutectic alloy of claim 11, wherein the impact strength of the hyper-eutectic alloy is 1.19 to 1.34 J/cm2.

13. The hyper-eutectic alloy of claim 1, wherein the hyper-eutectic alloy does not comprise a β-Al5FeSi (4′) phase.

14. A hyper-eutectic alloy with improved elongation and impact strength, the hyper-eutectic alloy consisting of 1.0 to 3.0 wt % of copper (Cu), 0.1 to 0.3 wt % of magnesium (Mg), 13.5 to 15.5 wt % of silicon (Si), 0.1 wt % or less of nickel (Ni), 0.5 wt % or less of iron (Fe), 0.1 wt % or less of manganese (Mn), 0.1 wt % or less of zinc (Zn) and a balance of aluminum (Al).