喷丸改性对7050铝合金FSW接头性能的影响

Effect of Shot Peening on Properties of 7050 Aluminum Alloy FSW Joint

对5 mm厚的7050铝合金搅拌摩擦焊接头进行喷丸表面改性处理,并对喷丸前后的接头进行残余应力测量、低周疲劳裂纹扩展试验,研究喷丸改性对焊接接头残余应力分布和焊核区、热影响区疲劳裂纹扩展速率的影响。结果表明,喷丸处理提高了接头表面粗糙程度,但接头表层及近表层产生硬化层,二次喷丸处理后的表层硬度值达198HV。二次喷丸最高硬度值比焊接态高33.1%。喷丸引入的残余压应力随喷丸次数增加而增大,最大压应力值位置也移向板材更深处。焊核区、热影响区疲劳裂纹扩展速率相对焊接态均降低,表明喷丸改性提高了接头两微区抗疲劳断裂的能力。

The 5 mm thick 7050 aluminum alloy friction stir welded joint was modified by shot peening modification.The residual stress measurement and low-cycle fatigue crack propagation test were carried out for the joints before and after shot peening.The effect of shot peening modification on the residual stress distribution of welded joints and the spread rate of fatigue cracks of nugget zone and heat affected zone were studied.The results show that shot peening treatment reduced the surface quality of the joints,but the surface layer and the near surface layer of the joint produce a hardened layer,and the hardness value of the surface layer after the secondary shot peening treatment reaches 198HV.The maximum hardness value of secondary shot peening is 33.1%higher than that of welding state.The residual compressive stress introduced by shot peening increases with the accumulation of the shot peening times,and the maximum pressure stress position moves deeper into the plate.The propagation rate of fatigue cracks of nugget zone and heat affected zone is reduced relative to the welded joint,which indicates the fatigue fracture resis-tance of the joint from the nugget zone and heat affected zone enhanced through the shot peening process.