600 ℃时钛合金高温低循环疲劳行为及其微观机理
发布人：上海艾荔艾合金股份有限公司www.shailiai.cn
更新时间：2016-01-14
研究近α型TG6钛合金盘锻件双态组织在600 ℃不同应变幅条件下的低循环疲劳行为，总应变幅∆εt/2控制在±0.6%～±1.5%，应变比R＝−1，采用三角波方式加载。
600 ℃时钛合金高温低循环疲劳行为及其微观机理High temperature low cycle fatigue behavior and its micro-mechanism of titanium alloy at 600 ℃研究近α型TG6钛合金盘锻件双态组织在600 ℃不同应变幅条件下的低循环疲劳行为，总应变幅∆εt/2控制在±0.6%～±1.5%，应变比R＝−1，采用三角波方式加载。结果表明：600 ℃低循环疲劳条件下，随着总应变幅的增加，循环峰值应力smax提高，而疲劳寿命Nf下降；对于TG6钛合金盘锻件双态组织，存在一个循环软化/硬化的总应变幅临界值(∆εt/2)c，约为±1.0%，当总应变幅高于此值，表现为循环硬化行为，而低于此值时，则表现为循环软化行为；在所有应变幅条件下，疲劳裂纹均为多源萌生模式，600 ℃低循环疲劳变形行为主要受α晶粒内位错的平面滑移所控制，位错平面滑移集中的结果是最早在α晶粒内萌生疲劳裂纹；随着疲劳测试温度的提高，不同滑移系上位错滑移的临界分切应力的差别缩小，促进位错交滑移的进行。
High temperature low cycle fatigue behavior and its micro-mechanism of near a TG6 titanium alloy disc forging with duplex microstructure in different strain amplitude at 600 ℃ were studied. The total strain amplitudes (∆εt/2) and strain ratio R were controlled at ±0.6%−±1.5% and −1, and tested with triangular waveform loading. The results show that the maximum tensile stress (smax) increases and the low cycle fatigue life (Nf) decreases with increasing ∆εt/2 under low cycle fatigue at 600 ℃. The critical total strain amplitude ((∆εt/2)c) of cyclic hardening and softening is about ±1.0% for TG6 titanium alloy disc forging with α+β microstructure, the cyclic hardening behavior dominates while the strain amplitude is above (∆εt/2)c, and the cyclic softening behavior dominates while the strain amplitude is below the (∆εt/2)c. The fatigue crack initiates at several origins under cyclic deformation at all strain amplitude. The LCF fatigue behavior is controlled by planar slip of dislocation and which may result in fatigue crack in the α grain. The difference of critical resolved shear stress (CRSS) at each slip plane is gradually reduced, and which may promote the cross slip of dislocations.
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