热处理对TC21合金组织形貌演变的影响

研究固溶温度及冷却速率对TC21合金组织演变的影响,采用定量软件对组织特征参数、晶粒大小、α相面积和片层厚度,及初生α相面积和次生α相厚度进行定量表征。结果表明,β相区处理时,随着固溶温度的升高,晶粒尺寸增大,且炉冷(FC)条件下晶粒长大的程度比包覆冷却(BC)的大(FCBC)。两相区热处理时,随着两相区热处理温度的升高(800～850℃),α相的总面积增加;在900～930℃固溶后,包覆冷却条件下,初始次生α相逐渐消失,α相总面积减小,而炉冷后,新的"羽毛"片状α相从β基体中大量析出,α相总面积反而增加。从动力学理论角度分析冷却速率对晶粒尺寸及α相体积分数变化的机制。

Effect of Heat Treatment on Microstructure Eolution of TC21 Alloy

The microstructure evolution was analysised by heat treatment process at different solution temperatures and different cooling rates above or below βtransform temperature.The microstructure parameters such as grain size,total α phase area,thicknesses of lamellar α phase,primary α phase area and secondary α phase area were measured by software Image Proplus.The results show that for the heat treatment above βtransform temperature with furnace cooling,the grain size increases with the increase of temperature,its growth is bigger than that under BC cooling condition at the same solution temperature,During the heat treatment below βtransform temperature,for BC cooling condition,the total α phase area increases with increasing of temperature(800-850 °C),while it decreases as result of the secondary α phase disappearance(after 900-930 °C solution treatment).Moreover,for FC cooling condition(900-930 °C),the total α phase area increases as result of the largely precipitation of feathery lamellar α phase.The evolution mechanism of the grain and the volume fraction of α phase were analysised by the dynamics theory.