液相线半连续铸造7075铝合金半固态组织演变

Evolution of the Semi-Solid Microstructures of 7075 Aluminum Alloy Cast by LSC

研究了液相线半连续铸造法生产的 70 75铝合金半固态浆料二次加热时组织的演变和主要合金元素的分布·结果表明 ,液相线铸造 70 75铝合金在相同加热温度下 ,随着保温时间的延长 ,晶粒尺寸与球化倾向增大 ;在相同保温时间下 ,随着加热温度的升高 ,晶粒尺寸与球化倾向也增加·加热温度 5 80℃左右 ,保温时间在 15～ 30min之间 ,和加热温度 6 0 0℃左右 ,保温时间在 5～ 15min之间 ,可以将半连续铸造锭坯中的蔷薇状和近球状组织转化为球形晶粒 ,晶粒的平均直径范围为 4 0～ 5 5 μm ,完全适合于半固态加工·液相线铸造 70 75铝合金二次加热组织中 ,主要合金元素Mg分布比较均匀 ,Cu在晶界处偏集严重 ,Zn在晶界偏聚较小·根据实验结果分析了液相线铸造 70 75铝合金在二次加热过程中组织演变机理·

The evolution of 7075 aluminum alloy 's microstructures and the distribution of the main elements were studied when the billets made by LSC were reheated. The grains are bigger and more globular with the holding temperature increasing when the holding time is stable, also with the holding time increasing when the holding temperature is stable. The rosette shaped and spheroidal grains can be turned into small and uniform global grains when the reheating temperature is about 580?℃ and the holding time is 15～30?min, or the reheating temperature is about 600?℃ and the holding time is 5～15?min. The grains average diameter is 40～55?μm which is suitable for thixoforming. The distribution of Mg is almost uniform, but Cu is seriously concentrated and Zn is slightly concentrated in the grain boundary after reheating. The mechanism of the evolution of the global grains from the as cast microstructures was analyzed.