钨添加对含锰β凝固γ-TiAl合金热加工性影响

Effect of tungsten addition on the hot workability of a Mn-containing β-solidifying γ-TiAl alloy

摘要:

为揭示微量W添加对含锰β凝固γ-TiAl合金热加工性的影响规律，采用真空感应熔炼炉（VIM）制备了Ti-42Al-5Mn-0.8W合金（原子百分比，下同），借助热模拟试验机研究了合金在变形温度1100~1250 ℃、应变速率0.001~10 s-1，变形程度为70%条件下的热变形行为。结果表明，合金合适的热加工区间为1150~1250℃/0.001~10 s-1和1100~1145 ℃/0.001~1 s-1。0.8 at.% W添加可明显降低Ti-42Al-5Mn合金的峰值流变应力（σp）和稳态流变应力（σ0.7），且稳态流变应力降低幅度更加显著。0.8 at.% W改善Ti-42Al-5Mn合金热加工性的主要原因一方面是由于W含量相对较少，在具有极强电磁搅拌作用的真空感应熔炼方式下，W元素的偏析程度并不明显；另一方面得益于W比Mn更强的β稳定作用，它的添加拓宽了合金高温β单相区，从而使合金具有更宽的可热变形窗口。

Abstract:

To reveal the effect of trace W addition on the hot workability of the Mn-containing β-solidifying γ-TiAl, the Ti-42Al-5Mn-0.8W alloy (at.%, the same below) were refined with a vacuum induction furnace. Hot deformation behavior of the alloy was studied at the temperature of 1100~1250 ℃, stran rate range of 0.001~10 s-1 and maximum deformation degree of 70% with thermal simulator. It shows that the range of appropriate thermal processing parameters are 1150~1250℃/0.001~10 s-1 and 1100~1145 ℃/0.001~1 s-1. 0.8 at.% W addition can obviously reduce the peak flow stress of Ti-42Al-5Mn alloy(σp) and steady-state flow stress(σ0.7), and the steady-state flow stress decreases more significantly. The main reason why 0.8 at.% W improves the hot workability of Ti-42Al-5Mn alloy is that on the one hand, the W content is relatively small, and the segregation degree of W element is not obvious under the vacuum induction melting mode with strong electromagnetic stirring; On the other hand, thanks to the fact that the β-stabilizing effect of W is stronger than that of Mn, extending the region of β single phase zone, thus having a wider processing window that can be thermally deformed.