AM50镁合金孔挤压强化对其疲劳性能的影响

Effects of Hole-expansion on Fatigue Property of AM50 Magnesium Alloy

目的研究孔挤压处理对AM50镁合金疲劳性能的影响。方法对AM50镁合金进行孔挤压强化处理,使试样表面产生有益的残余压应力分布,并对残余应力的分布进行测定。对未处理镁合金及孔挤压镁合金进行疲劳性能测试,对比疲劳寿命及疲劳裂纹扩展速率,对疲劳断口进行扫描,分析孔挤压对AM50镁合金疲劳性能的影响。结果孔挤压处理后,孔周围残余压应力深度达到5.5 mm,且最大压应力值达-563 MPa,试样的疲劳寿命较未处理时增加了9倍,疲劳裂纹扩展速率大大降低,疲劳裂纹源由未处理时的孔表面转移到了挤压强化层内部。结论孔挤压可以明显抑制疲劳裂纹的萌生,延长疲劳寿命。

Objective To investigate the effects of holeexpansion on fatigue property of AM50 magnesium alloy. Methods AM 50 magnesium alloy was treated by holeexpansion, and beneficial compressive residual stress was introduced onto the sample sur face, which was measured by Xray diffraction technique. Meanwhile, the fatigue properties of both untreated and untreated sam ples were tested under sinusoidal wave load, the fatigue life and fatigue crack growth rate were analyzed, and the effects of holeex pansion on fatigue properties of AM50 magnesium alloy were studied. The fatigue fracture was analyzed by the SEM technique. Re sults The experimental results showed that the compressive residual stress layer reached 5.5 mm around the hole after holeexpan sion, and the maximum value was 563 MPa. Fatigue life increased from 28 936 cycles to 300 556 cycles by 9 times, while the fa tigue crack growth rate greatly decreased. Conclusion SEM analysis showed that the fatigue initiation transferred inside the holeex pansion layer, which indicated that holeexpansion could obviously inhibit fatigue crack initiation and effectively enhance fatigue life.