Microstructural Evolution of AZ91D-1.5%Er during Semi-Solid Isothermal Treatment

Abstract:

In this paper, chip recycling technology combined with SIMA method which is called CR-SIMA method was adopted to prepare semi-solid billets. AZ91D magnesium alloy was refined by Er and its microstructural evolution was investigated during semi-solid isothermal treatment. The results show that Er can improve the feature of cast structure and decrease the grain size. Moreover, the γ-Mg₁₇Al₁₂ phase is well refined and disperses in the α-Mg matrix. A semisolid microstructure with small and spheroidal primary particles can be obtained after partially remelting. With increasing heating temperature, the dissolution of eutectic Mg₁₇Al₁₂ phase first took place, resulting in the primary dendritic grains coarsening into interconnected non-dendritic grains. With heating continuously, the residual interdendritic γ-Mg₁₇Al₁₂ at the edges of the primary grains melted in succession and the primary grains separated into small polygon grains. During the semi-solid isothermal treatment, the amount of liquid increased until the solid-liquid system reached its equilibrium state. At the same time, owing to the decreasing of interfacial energy, the grains gradually spheroidized and began to grow with a further increasing of the holding time.

• Periodical: Solid State Phenomena (Volumes 192-193)
• Pages: 238-245
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.192-193.238
• Online since: October 2012
• Authors: Hong Yu Xu, Ze Sheng Ji, Zhen Yu Wang
• Keywords: AZ91D, CR-SIMA, ER, Microstructural Evolution

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