Mn对L_(10)-TiAl金属间化合物延性的改善作用

本研究测定了64wt-％ Ti+(36-X)wt-％ Al+Xwt-％Mn(X=0,0.5,1.0,1.5,2.0)合金系列的抗弯性能,实验结果表明:适量的Mn可以显著地改善TiAl金属间化合的的延性。本文从合金组织、晶体结构及位错组态的变化出发,探讨了Mn的作用机制,得出了如下结论:a.Mn的加入使TiAl合金的晶粒显著细化,减少位错在晶内的塞积长度,从而较难造成裂纹形核所需的应力集中,同时裂纹在位向不同的晶粒内传播也更困难,使合金在断裂前可承受较大的变形。b.TiAl合金的晶格常数轴比(c/a)随Mn含量的增加而趋近于1,提高了晶体的对称性和变形协调性。c.Mn具有稳定TiAl合金中孪晶组织的作用,使TiAl合金的孪生变形较为容易,从而,当正常位错发生缠结、不能对塑性变形进一步作出贡献时,孪生变形将起着主要作用。d.与TiAl二元合金相比,变形后的TiAl+Mn三元合金中,层错明显增多,这表明超位错的运动对TiAl+Mn合金的塑性变形也起着重要的作用。

DUCTILITY IMPROVEMENT OF L_(10)-TiAI INTERMETALLIC COMPOUNDS BY THE ADDITION OF Mn

The bending properties of alloys, 64 wt-% Ti+(36-X) wt-% Al+X wt-%Mn (X = 0, 0.5, 1.0, 1.5, 2.0), were determined. The results showed that theaddition of suitable amount of Mn to TiAl intermetallic compounds could improvetheir ductility remarkably. In this research, with the purpose of understandingthe effect of Mn addition on the improvement of room-temperature ductility,the changes in the grain size, crystal and dislocation structures of TiAl with theaddition of Mn were studied. It was concluded that the ductility improvement withMn addition might be related to the following factors: (a)fineness of microstruc-tures, (b) decrease of c/a ratio close to 1 from 1.02, (c) twin stabilization and(d) movement of superdislocations.