Ti-Al系金属间化合物在均匀化热处理中的微观结构演变

Microstructure evolution of Ti-Al intermetallics during homogenization heat treatment

采用旋转摩擦挤压合金化技术制备Ti-Al合金试样,随后对其进行均匀化热处理以获得原位自生Ti-Al金属间化合物.利用SEM、EDS、XRD和EBSD等方法分析了均匀化热处理下Ti-Al试样微观结构的演变.结果表明:均匀化热处理后,组织发生了回复与再结晶现象,晶粒发生明显长大;同时,随着均匀化温度从450℃增至550℃,单质Ti不断减少,试样中出现亚稳相TiAl2和平衡相TiAl3.与室温试样相比,试样在500℃保温5h后,晶粒尺寸增大了4倍,TiAl3晶粒织构从初始的(9211)[0112],演变为(7911)[7811];而试样晶粒取向差范围从初始的3.8° ~114.4°缩小到3° ~92°,同时晶粒内部的晶界数量较原始晶粒下降了一个数量级.

Ti/Al alloys were prepared by rotating friction extrusion alloying method,then homogenization heat treated to obtain in-situ selfgenerated Ti-Al intermetallics.The microstructure evolution of Ti-Al alloy after homogenization was analyzed by means of SEM,EDS,XRD and EBSD.The results show that after homogenization the microstructure is recovered and recrystallized,and the grain size increases obviously.At the same time,free Ti is continuously reduced,then the metastable phase TiAl2 and equilibrium phase TiAl3 appear continuously with the temperature increasing from 450℃to 550℃.Compared with the sample at room temperature,the grain size increases four times,and the texture of TiAl3 grains is evolved from the initial(9211)[0112] into(7911)[7811] in the sample treated at 500℃for 5 h.However,the grain orientation misfit range is changed from the original 3.8°-114.4°into 3°-92°,and the amount of grain boundary is about an order of magnitude less than that of the initial sample.