β-CEZ钛合金热变形行为及热加工工艺

Hot deformation behavior and thermo-mechanical processing ofβ-CEZ titanium alloy

采用Gleeble-3800热模拟试验机在变形温度800~1000℃、应变速率0.01~10 s^（-1）的条件下对β-CEZ钛合金进行热模拟试验,分析了合金的真应力-真应变曲线和热加工图,并在此基础上研究了棒坯一次镦拔和多次镦拔工艺对合金显微组织和力学性能的影响。结果表明：β-CEZ钛合金流变应力随变形温度的升高而降低,但应力降低的幅度是越来越小,流变应力随变形速率的增大而匀速增大。热加工图稳定区主要分布在变形温度850~900℃,应变速率0.01~0.1 s^（-1）和变形温度925~975℃,应变速率0.1~0.7 s^（-1）的范围内。β-CEZ钛合金在相变点温度以下进行一次镦拔后,显微组织中晶粒较粗大且大小不一,β晶界不明显,晶粒内有板条状α析出。β-CEZ钛合金经过多次镦拔后,等轴组织明显得到细化和均匀化,β晶界非常清晰,等轴晶内有细小的针状和短板条状α析出,且纵横向显微组织差异小。多次镦拔后,断面收缩率明显提高,从而改善了合金的综合力学性能。

The hot deformation behavior of β-CEZ titanium alloy under the condition of 800-1000 ℃ and 0. 01-10 s^（-1） has been studied by hot compressing testing on a Gleeble-3800 simulator. Effects of single and multiple upsetting and cogging on microstructure and mechanical properties of the β-CEZ titanium alloy were investigated on the basis of true stress-true strain curves and thermomechanical processing map.The results show that the alloy decreases with the increase of deformation temperature,but the degree of the flow stress reduction is getting smaller and smaller. The flow stress of the alloy increases uniformly with the increase of the strain rate. The stable regions of the thermomechanical processing map are mainly located at two regions： one is 850-900 ℃ and 0. 01-0. 1 s^（-1）,the other one is 925-975 ℃ and0. 1-0. 7 s^（-1）. For the alloy with single upsetting and cogging under the phase transformation temperature,the grain is relatively coarse and the size is non-uniform,β grain boundary are not distinct and lath-shaped α phases precipitate in the grain. However,for the alloy with multiple upsetting and cogging,the equiaxed morphologies become refiner and uniformed,β grain boundary is very clear,small acicular and lathshape α-phase also precipitate in the equiaxed grain,and the microstructure difference is small between transverse direction and longitudinal one. The multiple upsetting and cogging can significantly improve the reduction of area and the comprehensive mechanical properties of the β-CEZ titanium alloy by the refined and uniform grain.