Effect of semi-solid isothermal heat treatment on the microstructure of Mg-6Al-1Zn-0.7Si alloy

摘要

In this paper, the effect of semi-solid isothermal heat treatment on the microstructure of Mg-6Al-1Zn-0.7Si alloy, especially on the semi-solid microstructural evolution and the modification of Chinese script shaped Mg{sub}2Si phase, are first investigated. The research results indicate that it is possible to produce the Mg-6Al-1Zn-0.7Si alloy with non-dendritic microstructure by the semi-solid isothermal heat treatment. After treated at 575-585℃ for 120 min, the experimental alloy can obtain a non-dendritic microstructure with a 12-21% liquid content and an average size range of 48-67 μm of the unmelted primary solid particles. In addition, the semi-solid isothermal heat treatment can modify the Chinese script shaped Mg{sub}2Si phases in experimental alloy. After treated at 580℃ or 585℃ for 120 min, the morphology of Mg{sub}2Si phases in the experimental alloy changes from the initial Chinese script shape to granule and/or polygon shapes.