Chen, Yiqing | Search NASA

DOE OSTI2019

Inhibiting Brittle Intermetallic Layer in Magnesium/Aluminum Bimetallic Castings via In Situ Formation of Mg{sub 2}Si Phase

A quasi-continuous Mg{sub 2}Si layer is formed in situ at the magnesium/aluminum interface of bimetallic castings, by selecting a Si-containing aluminum alloy and overcasting process control. This effectively inhibits the formation of brittle intermetallic compounds (Al{sub 3}Mg{sub 2}, Al{sub 12}Mg{sub 17}) during the casting process, and the mechanisms are discussed based on phase diagram calculations and experimental validation. It is, thus, recommended to select Si-containing Al alloys as substrate for Mg/Al bimetallic castings.

36 MATERIALS SCIENCE↗

DOE OSTI2015

A study on atomic diffusion behaviours in an Al-Mg compound casting process

Al and Mg alloys are main lightweight alloys of research interest and they both have superb material properties, i.e., low density and high specific strength, etc. Being different from Al alloys, the corrosion of Mg alloys is much more difficult to control. Therefore to combine merits of these two lightweight alloys as a composite-like structure is an ideal solution through using Al alloys as a protective layer for Mg alloys. Compound casting is a realistic technique to manufacture such a bi-metal structure. In this study, a compound casting technique is employed to fabricate bi-layered samples using Al and Mg and then the samples are analysed using electron probe micro-analyzer (EPMA) to determine diffusion behaviours between Al and Mg. The diffusion mechanism and behaviours between Al and Mg are studied numerically at atomic scale using molecular dynamics (MD) and parametric studies are conducted to find out influences of ambient temperature and pressure on the diffusion behaviours between Al and Mg. The results obtained clearly show the effectiveness of the compound casting process to increase the diffusion between Al and Mg and thus create the Al-base protection layer for Mg.

36 MATERIALS SCIENCE↗