微量B对铸态TiAl基合金显微组织及热变形行为的影响

Effect of trace boron element on microstructure and hot deformation behaviors of as-cast TiAl based alloy

采用电弧熔炼法制备含微量B元素的Ti-43Al-4Nb-1.4W-xB（x=0.2,0.4,0.6,0.8。数据为原子分数,%）合金;利用光学显微镜（OM）和扫描电镜（SEM）研究B含量对该铸态合金显微组织的影响,并通过热模拟压缩试验研究温度为1 050~1 200℃、应变速率为10 3~1 s 1的变形条件下Ti-43Al-4Nb-1.4W-0.6B合金的热变形行为,分析该合金在不同变形条件下的组织演化规律。结果表明：当B含量（质量分数）达到0.6%时,合金组织明显细化;Ti-43Al-4Nb-1.4W-0.6B合金的高温压缩流变应力随变形速率增加以及变形温度降低而增加;其峰值应力与变形条件之间的函数关系可用双曲正弦函数来描述,并以此求得高温变形激活能为580.68 kJ/mol;加入0.6%B对合金动态再结晶形核起到一定的促进作用,热变形后,合金发生明显的动态再结晶。

The effect of B content on the microsmacture and hot deformation behavors of as-cast Ti-43A1-4Nb-l.4W-xB alloy was systematically investigated using optical microscopy and scanning electron microscopy. The hot deformation behaviors of the Ti-43A1-4Nb-l.4W-0.6B alloy at temperatures from 1 050 ℃ to 1 200 ℃ with strain rates from 10-3to 1 s-1 were studied by thermal simulation compression tests. The results indicate that a refined microstructure for as-cast Ti-43A1-4Nb-1.4W-xB alloy can be obtained when the content of B reaches to 0.6%. The flow stress of Ti-43A1-4Nb-l.4W-0.6B alloy increases with increasing strain rate and decreasing deformation temperature. The relationship between peak stress and deformation conditions for the alloy can be described by a hyperbolic-sine type equation, and the apparent activation energy calculated is 580.68 kJ/mol. Dynamic recrystallization occurs apparently during hot deformation of the alloy. The addition of 0.6% B can accelerate the nucleation of dynamic recrystallization of the alloy.