铸造高铌TiAl合金双态组织转变过程

Duplex microstructure transformation of a cast high-Nb containing TiAl alloy

通过对Ti-46Al-8Nb-2Mn-0.2B合金的铸态组织和经过α+γ双相区热处理后的组织进行光学和扫描电镜进行观察,发现原始铸态组织的γ相偏析处不是片层的晶界,而是片层穿越的区域.由于γ相偏析区域的Al含量比片层基体高,因此阻碍了后续回火过程中该偏析部位片层的分解.通过先得到近γ组织,然后经过α+γ双相区保温,最终得到晶粒为40μm的双态组织;但组织中有少量的β相没有得到消除.

The as-cast structure and microstructure obtained after heat-treatment in the α＋γ field of a Ti- 46Al-8Nb-2Mn-0.2B alloy were studied. Optical and SEM observations show that the γ phase segregation region is not the grain boundary of the alloy but part of the α ＋ γ lamella. The Al content at the γ phase segregation region is a little more than the α ＋ γ lamella matrix, but it can play an important role in stabilizing the lamella and does harm to the break-up at the γ phase segregation region. By obtaining near γ microstructure firstly in the alloy and then heat-treating it in the middle region of the α ＋ γ field, the duplex microstructure with a grain size of 40μm can be formed, but a little of β phase still exists.