W对Ti-42Al-5Mn凝固组织与元素分配行为的影响

Effect of W addition on the solidification microstructure and element distribution behavior in Ti-42Al-5Mn alloy

摘要:

以低成本、易变形的Ti-42Al-5Mn合金（原子分数，下同）为研究对象，系统研究了0.5~1.0 at.%W含量对合金凝固组织和元素在相中分配行为的影响。结果表明，采用CaO坩埚一次真空感应熔炼方法制备的合金铸锭不同位置难熔金属W分布均匀且O含量控制在556~660 ppm。W添加后，合金凝固组织得到明显细化，随着W含量的增加，凝固组织中片层组织尺寸降低、含量减少。通过对不同相合金元素分布行为特征分析发现，Al在合金不同相中的富集顺序为：γ＞α2＞βo，Ti、Mn、W的为：βo＞α2＞γ，W添加不能改变Ti、Al元素在相关相中的分配行为，但会在一定程度上改变Mn元素的分配行为。随着W含量的增加，W在βo和α2相中的分配系数线性增加，分别满足kWα2/γ=1.4026CW(at.%)+0.4313，kWβo/γ = 1.3290CW(at.%) +1.8745，且W在βo相中的富集倾向约为Mn的5.6倍，在α2相中的富集倾向约为Mn的7.5倍。

Abstract:

The effects of 0.5~1.0 at.% W contents on the solidification microstructure and element distribution behavior in the βo,α2,γ phases of Ti-42Al-5Mn alloy (at.%, the same below) with low cost and good hotworkability were systematically studied. The results show that the refractory metal W in different positions of the alloy ingots prepared by one-step vacuum induction melting with CaO crucible is evenly distributed, and the O content is controlled in the range of 556 ~ 560 ppm. The solidification microstructure can be refined by W addition, and the lamellar structure size and content are generally decreased with the increase of W content. By analyzing the distribution behavior of alloying elements in different phases, it is found that the enrichment order of Al in different phases is as follows: γ＞α2＞βo, while those of Ti, Mn and W are all: βo＞α2＞γ. W addition cannot change the distribution behavior of Ti and Al, but will change the distribution behavior of Mn to a certain extent. The partitioning coefficients of W in α2 and βo phases are generally increased linearly with its content rised, and they meet kWα2/γ=1.4026CW(at.%)+0.4313, kWβo/γ=1.3290CW(at.%)+1.8745,respectively. In Ti-42Al-5Mn alloy, the enrichment tendency of W in βo phase is about 5.6 times that of Mn, and the enrichment tendency in phase α2 is about 7.5 times that of Mn.