形变诱导法半固态加热工艺参数对LY12合金组织和晶粒尺寸的影响

Effect of semi-solid melting factors on structure and grain size of LY12 alloy in SIMA processing

对LY12合金采用形变诱导法制备半固态合金料坯的组织演变过程进行了观察 ,对变形率、半固态温度、半固态保温时间对合金半固态组织和晶粒尺寸的影响进行了研究。组织演变过程观察表明 :用形变诱导法制备该合金半固态坯料的合适的半固态重熔温度为 6 18℃ ;合金在该温度重熔过程中 ,形变带状组织首先分解为细小的α多边形晶粒 ,随保温时间的延长 ,晶粒尺寸逐渐变大 ,同时α相逐渐球化 ;在相同的半固态温度和相同的保温时间下 ,宏观变形率大的晶粒尺寸要比变形率小的合金组织晶粒尺寸小 ;变形率大的试样比变形率小的液相出现时间早 ;在同一宏观变形率下 。

Structure evolution of LY12 alloy in remelting procedure in strain induced melt activated (SIMA) semi-solid processing was observed, and effects of the factors, remelting temperature, holding time and strain rate, on structure and grain size of the alloy were investigated. The results show that the proper remelting temperature is 618?℃ and in the remelting procedure, small polygon α crystals are initially formed from breaking the original strip structure obtained during pressing and then grow larger along with more spherical shape. The grain size in the specimen with greater strain rate is smaller than that with smaller one in the same remelting temperature and holding time. Liquid emerges earlier in the specimen with greater strain rate than in the specimen with smaller macroscopic strain rate. The grain size in the location with greater microscopic strain rate in a specimen with a certain macroscopic strain rate is smaller than that in the location with smaller microscopic strain rate.