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

以低成本、易变形的Ti-42Al-5Mn合金(原子分数,下同)为研究对象,研究了0.5at%~1.0at%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556~660μg/g。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,且凝固组织显微硬度得到明显提升。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>α_(2)>β_(o),Ti、Mn、W的为:β_(o)>α_(2)>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β_(o)和α_(2)相中的分配系数线性增加,分别满足k_(α_(2)/γ)^(w)=1.4026CW(at%)+0.4313,k_(β_(o)/γ)^(W)=1.3290C_(W)(at%)+1.8745,且W在β_(o)相中的富集倾向约为Mn的5.6倍,在α_(2)相中的富集倾向约为Mn的7.5倍。

The effects of 0.5at%~1.0at%W contents on the solidification microstructure and element distribution behavior in the β_(o),α_(2),γphases of Ti-42Al-5Mn alloy(at%,the same below)with low cost and good hot workability were 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 556~660μg/g.The solidification microstructure can be refined by W addition,and the size and content of the lamellar structure generally decrease with the increase of W content.The micro-hardness test suggests that the hardness increases 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>α_(2)>β_(o),while those of Ti,Mn and W are all:β_(o)>α_(2)>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 α_(2) and β_(o) phases generally increase linearly with the increase of its content,and they meet k_(α_(2)/γ)^(W)=1.4026CW(at%)+0.4313,k_(β_(o)/γ)^(W)=1.3290CW(at%)+1.8745,respectively.In Ti-42Al-5Mn alloy,the enrichment tendency of W in β_(o)phase is about 5.6 times that of Mn,and the enrichment tendency in phaseα_(2) is about 7.5 times that of Mn.