采用拉压对称的机械应变控制, 研究了Ti-6-22-22合金在200~400℃和200~520℃两个温度范围的热机械疲劳(TMF)行为. 结果表明, 在200~400℃内, 同相和反相热机械疲劳寿命均高于400℃等温疲劳寿命; 在200~520℃范围, 反相热机械疲劳寿命明显低于520℃等温疲劳寿命. 在两个温度范围内, 热机械疲劳的循环应力都与相应等温疲劳的循环应力响应有关. 纵向剖面金相观察表明, 520℃时等温疲劳表面的裂纹更长. 循环温度范围扩大导致环境破坏作用增强是热机械疲劳具有明显破坏作用的原因.
The thermo--mechanical fatigue (TMF) behaviors of Ti--6--22--22 alloy were investigated in full reverse mechanical strain control in the temperature ranges from 200 to 400℃ and 200 to 520℃. Experimental results indicate that from 200 to 400℃, the fatigue lifes of in phase and out of phase are longer than that of isothermal fatigue (IF) at 400℃; from 200℃ to 520℃, the fatigue life of out--of--phase is much shorter than that of IF at 520℃. The amplitude of cyclic stress of TMF is related to the maximum and minimum temperatures of TMF in the two cyclic temperature ranges. Observations of fracture surface by longitudinal sections by metallography reveal that longer surface cracks appear under IF at 520℃. The reason for obvious detrimental effects of TMF may result from the enhanced environmental damage due to the increase of cyclic temperature range.
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