喷丸强化覆铝7B04-T7451铝合金的表面完整性及疲劳性能研究

Investigation on Surface Integrity and Fatigue Properties of Aluminum-Clad 7B04-T7451 Alloy Treated by Shot Peening

研究了喷丸强化对覆铝7B04-T7451铝合金表面完整性和疲劳性能影响,阐明了覆铝层对喷丸强化效果的影响。采用维氏硬度计、原位纳米测试系统、激光共聚焦显微镜、X射线衍射仪等,分析了喷丸强化后试样的显微硬度、表面轮廓、表面粗糙度及残余应力等的变化。利用疲劳试验机测试喷丸强化试样的疲劳寿命,利用扫描电镜分析疲劳断裂断口的特征。结果表明,喷丸强化覆铝7B04-T7451试样表层硬度从表层向内部逐渐增大,直到基材硬度,表面硬度较原始试样略有提高;覆铝7B04-T7451试样表面发生剧烈的塑性形变,弹丸尺寸较大,表面粗糙度明显增大;喷丸强化引入深度约150μm的残余压应力层,但其残余压应力数值和应力峰值均较小。喷丸强化覆铝7B04-T7451铝合金的疲劳性能没有获得提高,由于表面粗糙度和塑性形变显著增大,使得疲劳裂纹源在覆铝层表面萌生较快,疲劳寿命降低。

The effect of shot peening on the surface integrity and fatigue properties of aluminum-clad 7B04–T7451 aluminum alloy was studied,and the effect of the aluminum-clad layer on the shot peening effect was clarified.Vickers hardness tester,in-situ nanometer testing system,laser confocal microscope,X-ray diffractometer were used to analyze the changes of microhardness,surface profile,surface roughness and residual stress of the samples after shot peening.The fatigue life of shot peening specimens was tested by fatigue testing machine and the characteristics of fatigue fracture were analyzed by scanning electron microscope.The results show that the hardness of the surface layer of the shot peened aluminum-clad 7B04–T7451 sample increases gradually from the surface to the interior until the hardness of the base material,and the surface hardness is slightly higher than that of the original sample;The larger the size,the larger the surface roughness is;The residual compressive stress layer with a depth of about 150μm is introduced by shot peening,but its residual compressive stress value and stress peak value are both small.The fatigue properties of the shot peening clad 7B04-T7451 aluminum alloy did not improve.Due to the significant increase in surface roughness and plastic deformation,the fatigue crack source was initiated faster on the surface of the aluminum-clad layer,and the fatigue life decreased.