一種TiAl合金高溫低循環(huán)疲勞性能及失效機(jī)理

一種TiAl合金高溫低循環(huán)疲勞性能及失效機(jī)理High Temperature Low Cycle Fatigue Properties and Failure Mechanism of a TiAl Alloy

通過對TiAl合金進(jìn)行總應(yīng)變范圍控制的高溫（750℃）低循環(huán)疲勞實(shí)驗(yàn)，研究雙態(tài)（Duplex，DP）和全片層（Fully Lamellar，F(xiàn)L）組織形態(tài)對TiAl合金低循環(huán)疲勞性能和壽命的影響，并采用總應(yīng)變幅-壽命方程對兩類組態(tài)TiAl合金低循環(huán)疲勞壽命進(jìn)行預(yù)測。結(jié)果表明：在相同溫度和應(yīng)變條件下，DP組態(tài)TiAl合金穩(wěn)態(tài)遲滯回線對應(yīng)的平均應(yīng)力明顯低于FL組態(tài)TiAl合金穩(wěn)態(tài)遲滯回線對應(yīng)的平均應(yīng)力；采用總應(yīng)變幅-疲勞壽命方程能夠準(zhǔn)確預(yù)測兩種組態(tài)TiAl合金在750 ℃下的疲勞壽命，預(yù)測壽命基本位于試驗(yàn)壽命的±2倍分散帶以內(nèi)；另外，DP組態(tài)TiAl合金的疲勞源區(qū)位于試樣的近心部，而FL組態(tài)TiAl合金的疲勞源區(qū)位于試樣的次表面，兩類組態(tài)TiAl合金的高溫疲勞失效機(jī)理存在明顯差異。

Total strain range controlled low cycle fatigue (LCF) experiments were conducted at 750 ℃ to investigate the effects of the duplex and fully lamellar microstructure on fatigue behavior and life of a TiAl alloy, and the total strain range-life equation was employed to predict LCF life of the alloy. The results show that the mean stress produced at hysteresis loop of TiAl alloy with DP is less that of TiAl alloy with FL at the same temperature and applied strain. The total strain range-life equation is able to predict the fatigue life of the alloy, and the predicted life is located between ±2 scatter band of the experimental life. In addition, the fatigue source of TiAl alloy with DP is located near center of the specimen while that of TiAl alloy with FL is located on subsurface of the specimen, and the failure mechanisms are obviously different between the two types of the TiAl alloy.

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