TiAl合金PST晶体断裂过程原位TEM观察

IN SITU STRAINING TEM OBSERVATION OF FRACTURE PROCESSES IN POLYSYNTHETICALLY TWINNED CRYSTALS OF TiAl

利用ＴＥＭ原位应变观察技术研究了ＴｉＡｌ合金ＰＳＴ晶体中裂纹扩展过程。发现界面与裂纹的交互作用与界面类型有关，不对称的伪孪晶界面（γ／γＰ）对裂纹扩展的阻碍最强烈。片层界面以及二次裂纹导致的裂纹分叉是层状组织韧化ＴｉＡｌ合金的重要原因。当裂纹与片层界面的夹角不同时，γ相所表现的两种截然不同的断裂方式表明在ＴｉＡｌ合金的脆性本质中包含有位错动力学的因素。

Crack propagation processes in polysynthetically twinned (PST) crystals of TiAl were investigated by in situ TEM observation. It was found that the influence of lamellar boundaries on the fracture behaviors is connected with the type of interfaces, in which the asymmetrical γ/γ P interface is the largest inhibition to crack growth. The crack kinks which result from lamellar interfaces and second microcracks play a dominant role on that TiAl alloys are toughened by lamellar structure. As the angle between tensile axis and lamellar interface varies, that two kinds of different fracture modes existed in γ phase indicates that dislocation dynamics may be an important reason on embrittlement of TiAl alloys.