择优取向层片组织TiAl合金的室温疲劳行为

采用旋转弯曲加载方式,评价了择优取向层片组织Ti-47.5Al-2.5V-1.0Cr-0.2Zr(原子数分数,%)合金的室温高周疲劳性能,并采用扫描电镜对疲劳断口进行了观察和分析。结果显示,实验合金的应力-寿命(S-N)曲线呈现平直形态,符合Basquin方程;其条件疲劳极限为477MPa,相当于其抗拉强度的83%。断口观察发现,疲劳试样以穿层片解理方式发生断裂。疲劳裂纹主要沿位于试样表面层、与外加应力成30°~90°的层片界面萌生,之后以穿层片方式发生扩展。在同一应力水平下,疲劳寿命随疲劳源尺寸增加而减少,疲劳源尺寸波动是导致疲劳寿命大幅分散的主要原因。

Room-temperature fatigue behavior of TiAl alloy with preferentially oriented lamellar microstructure

The room-temperature high-cycle fatigue performance of Ti-47.5Al-2.5V-1.0Cr-0.2Zr (at.%)alloy with a preferentially oriented lamellar microstructure has been evaluated by load-controlled rotating bending fatigue tests,and the fracture surfaces have also been observed and analyzed by scanning electron microscopy.The results show that the studied alloy exhibits a flat S-N curve which follows the Basquin equation.The fatigue limit is 477 MPa,which equals to 83% of the ultimate tensile strength.The fracture surface observation proves that the fail-ure of these specimens is caused by a translamellar cleavage mode.Fatigue cracks mostly initiate along lamellar in-terfaces which located at specimens′surface and also have an angle of 30°-90°with the applied stress,and then propagate in a translamellar way.Moreover,at the same stress level,fatigue life decreases with increasing the size of crack initiator,and the large fatigue-life scatter of the studied alloy mainly results from the variability of crack-initiator size.