全层TiAl合金架桥韧带的作用研究

通过对直缺口近全层组织的扫描电镜原位拉伸实验以及相应的断裂表面观察,研究了全层铸状TiAl基合金组织两个团厚度拉伸试样的拉伸断裂机理.研究结果表明:新裂纹形核过程中架桥韧带的形成过程实质上降低了裂纹扩展抗力;在架桥韧带撕裂瞬间出现外加应力的增加,实际上是由于裂纹从一沿层开裂向穿层开裂过渡的结果.许多裂纹是表面裂纹,所以显微裂纹屏蔽的作用并不明显.

Effect of bridging ligament within fully lamellar TiAl alloy

By means of in-situ-tensile experiment on the straight notched specimens of a directionally solidified cast fully lamellar TiAl alloy and corresponding observation upon its fracture surface with SEM,and considering their mutual intrinsic relationship,the crack propagation process and fracture mechanism of that specimens with two-colony thickness was investigated.It is shown that the processes of new crack nucleation with bridging ligament formation decreases the crack propagation resistance rather than increasing it.The increase of applied stress which appear,at the moment of tearing of bridging ligament is actually attributed to the transition of crack from an inter-lamellar propagation to a trans-lamellar propagation.A lot of microcracks are surface cracks,and the effect of microcracks shielding is not obvious.