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Indexed by:期刊论文

Date of Publication:2019-04-01

Journal:METALS

Included Journals:SCIE

Volume:9

Issue:4

ISSN No.:2075-4701

Key Words:magnesium alloy; semi-solid; isothermal coarsening; microstructure evolution

Abstract:A semi-solid microstructure of Mg-10Zn-6.8Gd-4Y alloys is acquired via an isothermal heat treatment process, and the effects of the holding time on the microstructure evolution of Mg-10Zn-6.8Gd-4Y alloys are investigated. The results show that the microstructure of the cast alloy is composed of primary -Mg dendritic grains with a eutectic structure (W-phase and eutectic Mg) distributed at the grain boundaries. The primary -Mg dendritic grains grow in size with increasing holding time, and they tend to grow into more globular structures in the initial stage; they then become a bit more dendritic, as small branches grow from the grain boundaries after holding the sample at 580 degrees C for 10 min. Meanwhile, the interdiffusion of magnesium atoms within the eutectic region, and between the primary -Mg and eutectic structure, leads to the formation of fine and relatively globular eutectic Mg grains in the eutectic structure after holding for 10 min. The eutectic Mg grains begin to grow, coarsen, coalesce, or be swallowed by the surrounding primary grains, causing fluctuations of the general grain size. Over the whole isothermal heat treatment process, two mechanismscoalescence and Ostwald ripeningdominate the grain coarsening.