Effect of cyclic heat treatment on microstructures and mechanical properties of directionally solidified Ti-46Al-6Nb alloy  

循环热处理对定向凝固Ti-46Al-6Nb合金组织和力学性能的影响（英文）

作　　者：方虹泽[1] 陈瑞润[1] Anton GETMAN 郭景杰[1] 丁宏升[1] 苏彦庆[1] 傅恒志[1] 

机构地区：[1]哈尔滨工业大学材料科学与工程学院,哈尔滨150001

出　　处：《Transactions of Nonferrous Metals Society of China》2015年第6期1872-1880,共9页中国有色金属学报（英文版）

基　　金：Project(2011CB605504) supported by the National Basic Research Program of China;Project(NCET-12-0153) supported by the Program of New Century Excellent Talents in University;Project(51274076) supported by the National Natural Science of Foundation of China

摘　　要：The Ti-46A1-6Nb （mole fraction, %） ingots that were directionally solidified by cold crucible were cyclic heat treated at 1330 ℃ in the a phase region. The microstructures and mechanical properties of the ingots before and after heat treatment were investigated. The results show that the large columnar grains are changed into equiaxed grains after heat treatment. The grain size decreases with increasing the cyclic times, which is caused by the recrystallization and the transition from the large grain of small lamellae to the small grain of large lamellae. Four times of cyclic heat treatment refines the grain size from 1.33 mm to 0.59 turn, nevertheless the lamellar spacing increases from 0.71 ~tm to 1.38 lim. Extending the holding time and increasing the cyclic times of heat treatment eliminate the fl-segregation at the grain boundary and the interlamellar. The compression testing shows that the compressive strength of the directionally solidified ingot in the parallel and perpendicular directions are 1385.09 MPa and 1267.79 MPa, respectively, which are improved to 1449.75 MPa and 1527.76 MPa after two and four times of cyclic heat treatment, respectively, while that is 1180.64 MPa for the as-cast sample. The fracture mode of the sample after cyclic heat treatment is quasi-cleavage fracture.利用冷坩埚定向凝固技术制备Ti-46Al-6Nb(摩尔分数,%)合金,然后对定向凝固铸锭进行热处理,热处理温度为1330°C,热处理区间在α相单相区。研究热处理前后铸锭显微组织和力学性能的变化。结果表明:铸锭经过热处理后,大的柱状晶转变为等轴晶。随着热处理循环次数的增加,晶粒尺寸减小,这是由于发生了再结晶和小片层的大晶粒与大片层的小晶粒之间的转变。四次循环热处理能够有效地细化晶粒尺寸,使晶粒尺寸从1.33 mm降低到0.59 mm,然而片层间距从0.71μm增加到1.38μm。延长保温时间和增加热处理循环次数能够消除晶粒间和片层间的β偏析相。压缩实验结果表明,对定向凝固铸锭,平行于柱状晶生长方向的压缩强度为1385.09MPa,垂直于柱状晶生长方向的压缩强度为1267.79 MPa;铸造试样的压缩强度为1180.64 MPa,经热处理循环两次后压缩强度提高到1449.75 MPa,热处理循环4次后压缩强度提高到1527.76 MPa。循环热处理后,合金试样的断裂方式为准解理断裂。

关 键 词：TiA1 alloy cyclic heat treatment directional solidification mechanical properties 

分 类 号：TG166.5[金属学及工艺—热处理]