Summary
The influence of different proportions of the chemical composition of the 380 die-cast alloy on the mechanical properties was analyzed. The results show that the 380 aluminum alloy formulated with high alloy content has higher tensile strength, yield strength, and hardness than the 380 aluminum alloy formulated with low alloy content, while the latter has high elongation, and the standard 380 aluminum alloy composition is in both. between. In practical applications, reasonable matching should be based on the specific requirements of the parts for mechanical properties.
Key words: 380 die-cast alloy chemical composition mechanical properties
Since the cold chamber die casting machine has been used, aluminum alloy has been widely used in the die casting industry for a long time. In the 1980s, in the United States die casting production, aluminum alloy accounted for 80%. With the passage of time and the need for production development, there are as many as 23 varieties incorporated into die-cast aluminum alloys, but the more typical ones are 380 aluminum alloys (similar to GD-AlSi9Cu3) that were adopted in the 1940s. The United States has developed three standards for this alloy, namely 380, A380 and B380. The typical chemical composition of these alloys is shown in Table 1 [1].
Table 1 Chemical composition of a typical 380 aluminum die casting alloy
~9.5 3.0
~ 4.0 2.0 0.50 0.10 0.50 3.0 0.35 0.50 remaining A380 7.5
~9.5 3.0
~4.0 1.3 0.50 0.10 0.50 3.0 0.35 0.50 Other B380 7.5
~9.5 3.0
~4.0 1.3 0.50 0.10 0.50 1.0 0.35 0.50 The rest
The difference in iron content and zinc content is the main difference between these alloys. The 380 contains 2% iron and can be produced on hot chamber die casting machines. A380 and B380 have a 1.3% iron content and are only used in cold chamber die casting machines. When this alloy began to set standards, only 380 and A380, their zinc content is limited to 1%. By the 1950s, the upper limit of zinc rose to 3%, so that the alloy containing 1% zinc was named B380. All these kinds of alloys have superior casting properties and high mechanical properties, and allow certain impurities, so 380 is a more basic common die casting alloy. The following describes the effect of the chemical composition on the microstructure and mechanical properties of the A380 alloy under normal production conditions. The chemical composition of the alloy is now divided into two upper (H) and lower (L) limits, measured at room temperature.
1 test plan
All the alloys and die-casting test bars were produced under the production conditions. Table 2 shows the variation ranges of the chemical composition of the alloys in the upper limit (H) and the lower limit (L).
Table 2 Variations of the chemical composition of the alloys for the two groups of tests
The standard test bars used for aluminum die castings are shown in Figure 1.
Figure 1 Aluminium die-cast standard test bar used in accordance with ASTM B557-84
The test bars after die casting should be cleaned and removed. 50 test bars should be cast with each alloy composition. The airtightness should be checked by fluoroscopy, and 35 dense bars should be selected from each component. carry out testing.
The die-cast test bars were tested after they were stored in the as-cast state for 45 days. Their tensile strength, yield strength and elongation were all measured according to ASTM standards. Since the test bars are not ideally circular, they must be accurately calculated. Cross-sectional area to reduce errors. Twenty test bars for each alloy were used for hardness testing and were measured by HRB.
The inspection of the test rods using optical microscopes, galvano-scanning electron microscopes, and fluoroscopy spectrometers clearly shows the composition, distribution, and composition of the various phases in the metallographic structure. A fracture surface light penetration test was performed again and a grating electron microscope examination was performed.
2 Mechanical properties test
The measured tensile strength, yield strength, elongation, and hardness data are shown in Table 3
Table 3 Measured values ​​of alloy mechanical properties in the two groups
MPa yield strength
MPa elongation
% Hardness
HRB(HB) L average 309.86 140.80 6.46 33.4(69.4) Lower value 285.32 47.01 4.3 21.2(62.1) Higher value 322.48 168.31 8.2 47.0(80.0) Standard error ±11.78 ±13.17 ±0.85 ±4.5(±9.4) Measuring accuracy ±3.5 ±3.5 ±0.2 ±1 (±2) H Average 345.72 221.81 2.55 62.3 (98.3) Lower 322.48 200.51 2.00 49.6 (82.6) Higher 364.54 241.33 3.05 71.0 (112.0) Standard error ± 7.17 ± 10.20 ± 0.28 ±3.5(±5.5) Measurement Accuracy±3.5 ±3.5 ±0.2 ±1(±2)
The lower values ​​of tensile strength and yield strength can be compared with the data developed by various standards and authoritative organizations. The specific content is shown in Table 4.
Table 4 Various Standard Values ​​of Alloy 380 Mechanical Properties
MPa yield limit
MPa elongation
% Hardness
HB 1 324 159 4.0 75 2 325 160 4.0 3 320 160 3.5 75 4 325 160 3.5 5 325 158 3.5 6 240 140 1.0 80
Note: Data sources are as follows:
1Rooy EL: Aluminium and Aluminium Alloys. ASTM Handbook, 9, Auf 1. Bd. 15, (1988), S. 743-770.
2ASTM Metal Handbook, 10, Auf1.Bd.2, (1990).
31992 Annual Book of ASTM Standards V.02.02.1992.
4ASTM Metal Handbook, 9, Auf1.Bd.2, (1979), S.170
5Aluminium Alloy A380 (Aluminium Die Casting Alloy). Metal Digest, Al-6q, Juni 1986.
6EN-Norm BZW.D1N 1725 Teil 2.
The Brinell hardness values ​​can be found in the data in Table 3 and converted to HRB. The standard error in Table 3 was determined from 35 test bars, and the hardness was measured from 200 test points in 20 test bars. Its performance is shown in Figure 2 to Figure 5.
Fig. 2 Proportion of test bars with different tensile strengths Figure 3 Proportion of test bars with different yield strengths
Figure 4 Proportion of test bars with different elongations Figure 5 Proportion of test bars with different hardness
3 Results Discussion
The chemical composition of A380 (GD-AlSi9Cu3) has a significant effect on the mechanical properties and metallographic structure. When formulated with a high alloy content (H), the tensile strength, yield strength, and hardness are 11.6%, 57.5%, and 86.5% higher, respectively, than the low alloy content (L). The elongation of the low alloy content (L) is 153% higher than that of the high alloy content (H). The standard value of the chemical composition of the A380 alloy is between high (H) and low (L).
The properties of the test bars molded from the same alloy also vary. For example, the 35 test bars cast from the alloy (L) have lower tensile strengths of 285 MPa and higher values ​​of 322 MPa. The average values ​​of the elongation, hardness, and yield strength errors were 36.4%, 60.4%, and 77.2%, respectively. With this data dispersion, the low alloy content (L) is more pronounced than the high alloy content (H). This degree of dispersion may be explained by the presence of segregation and changes in process parameters in the alloy. If the chemical composition reaches a better value and the process parameters are strictly controlled, the mechanical properties of the material will reach a higher level.
Author brief introduction; Wang Yizhi, male, born in 1925, professor, Shanghai Jiaotong University (200030)
Author unit: Wang Yizhi (Shanghai Jiaotong University)
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