不同应变比下γ-TiAl合金疲劳裂纹扩展机理

Fatigue Crack Propagation Mechanism of γ-TiAl Alloy under Different Strain Ratios

运用分子动力学方法研究了γ-TiAl合金在不同应变比作用下的疲劳裂纹扩展机理。结果表明,疲劳裂纹均先以解理方式扩展,随后通过驱动力驱动无序区域扩展,最后转变为子–母裂纹传播机制扩展,其差别在于不同应变比作用下裂纹扩展方式的转变发生在不同的时刻;在塑性变形中,应变比的不同使得位错在不同时刻被发射出来且沿不同平面滑移,并且位错在滑移时有不同点缺陷形成如空位、双空位、三空位等,同时,应变比的不同也使得堆垛层错沿着不同密排面形成和扩展。

The mechanism of fatigue crack propagation of γ-TiAl alloy under different strain ratios was studied using the molecular dynamics method.The results show that a fatigue crack propagates in the manner of cleavage firstly,and then propagates through disordered region by driving force.Finally,it changes into sub-main crack mechanisms.The difference is that the change in the mode of crack propagation occurs at different time under different strain ratios.At the stage of plastic deformation,dislocations emit at different time and glide at different planes due to different strain ratios.Defects,such as vacancies,divacancies,and trivacancies,are generated during dislocation gliding.Meanwhile,stacking faults are generated along the different close-packed planes under different strain ratios.