(甘肃工业大学 材料科学与工程学院，兰州 730050)
摘 要: 研究了未变质处理和变质处理的AZ91D镁合金在半固态等温热处理过程中的组织演变，并对其组织演变机理进行了探讨。结果表明 AZ91D镁合金在液-固相区570℃等温处理时，未变质处理的δ相由粗大的树枝晶演变为大块状，随后δ相发生熔化分离，并在半固态等温过程中演变为球状，初生相最小尺寸可达50～80μm； 变质处理的初生δ相由等轴晶演变为小块状，随后进一步熔化分离为更细小的块状，接着逐渐演变为球状组织，初生相最小尺寸可达20～60μm。等温处理时间过长时，两种组织都会发生合并长大。
关键字: 镁合金； 半固态成形； 半固态等温热处理；球状组织
during semi-solid isothermal heat treatment
（College of Materials Science and Engineering，
Gansu University of Technology， Lanzhou 730050， P.R.China）
Abstract:The structure evolution of AZ91D magnesium alloy and the modified AZ91D magnesium alloy during semi-solid isothermal heat treatment was studied， and its transformation mechanism was also discussed. It was found that， when AZ91D magnesium alloy is treated at semi-solid temperature 570 ℃， the primary δphase changes from the large dendritic structure to the large nubbly， and then to be melt and separated into the small nubbly. With isothermal times increasing， the small nubbly changes to spheroidal grains and the primary δ phase is formed about 50～80μm. Therefore， the primary δ phase which is modified changes from equiaxed grains to small nubbly， then it is separated into smaller nubbly. With increasing isothermal times， it changs to the smaller spheroidal grains than its non-modification does and is formed about 20～60 μm.
Key words: magnesium alloy; semi-solid forming； semi solid isothermal heat-treatment； spheroidal structure
