Affiliation:
1. School of Materials Science and Engineering, Sichuan University, Chengdu, China
2. China Science Lab, General Motor’s Global Research and Development, Shanghai, China
Abstract
Adding Cr to Al–Si–Mg alloys can eliminate the adverse effects of Fe, but can increase the quench sensitivity of the alloys. The influence of gravity-casting and high-pressure die-casting on the quench sensitivity of A379 (Al–7Si–0.5Mg–0.2Cr) alloys were studied using time–temperature–property curves. The nose temperatures of the gravity-casting- and high-pressure die-casting-fabricated specimens are near 350 °C and 355 °C, respectively. The temperature regions with high quench sensitivity characteristics of the former and latter occur from 310 °C to 390 °C and from 290 °C to 400 °C, respectively. The time–temperature–property curves of the high-pressure die-casting-fabricated samples are farther to the left than that of gravity-casting-fabricated samples, indicating that the high-pressure die-casting-fabricated specimens are more sensitive and are easier to generate precipitates than the gravity-casting-fabricated specimens during quenching because of the following reasons. For both specimens, the quench-induced precipitates (Mg xSi) nucleate on the Cr-containing dispersions in the grains, but the Cr-containing dispersions in the high-pressure die-casting-fabricated specimens are finer and more dispersible than in the gravity-casting-fabricated specimens. Meanwhile, the high-pressure die-casting-fabricated specimens exhibited finer grain sizes than the gravity-casting-fabricated specimens; thus, they can provide more grain boundary nucleation sites for forming the Mg xSi phase than the gravity-casting-fabricated specimens during isothermal treatment.
Subject
Mechanical Engineering,General Materials Science
Cited by
2 articles.
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