应变比对复合细化超细晶纯钛低周疲劳行为的影响

Effect of Strain Ratio on Low Cycle Fatigue Behavior of Ultra-fine Grained Titanium

摘要:

采用等径通道弯曲挤压(Equal Channel Angular Pressing, ECAP)+旋锻(Rotary Swaging, RS)技术制备超细晶纯钛，细化后晶粒尺寸达到纳米级。在室温下对超细晶纯钛实施应变比分别为-1、-0.5、0.5的应变控制低周疲劳试验，通过TEM对微观组织观察。研究了应变比对材料循环硬化软化特性、循环应力应变关系及疲劳寿命的影响。研究结果表明，应变比增大使得超细晶纯钛循环硬化现象更为显著，应变比越大超细晶纯钛低周疲劳寿命越低。低周疲劳高应变比情况下亚晶晶粒尺寸小，数量多，阻碍位错运动，使得材料发生循环硬化。

Abstract:

Ultra-fine grained (UFG) pure titanium was prepared by equal channel angular pressing (ECAP) and rotary swaging (RS). Low cycle fatigue tests with strain ratios of - 1, - 0.5 and 0.5 for titanium were carried out at room temperature. Microstructure was observed by TEM after the fatigue test. The effects of strain ratio on cyclic hardening and softening properties, cyclic stress-strain relationship and fatigue life of materials were studied. The results show that the cyclic hardening of UFG pure titanium is more obvious with the increase of strain ratio; Low cycle fatigue life of ultra-fine grained pure titanium decreases with increasing strain ratio; Microstructure observation shows that under high strain ratio, the subgrain size is small and the number of subgrains is large, which hinders the movement of dislocations and leads to cyclic hardening.