激光冲击-超声滚压复合工艺对AZ91D镁合金力学性能的影响

Effect of laser shock peening and ultrasound surface rolling combined processes on mechanical properties of AZ91D Mg alloy

采用Nd:YAG激光冲击强化及超声滚压对AZ91D镁合金进行了表面强化处理,并进行了拉伸试验及断口观察,分析了材料的残余应力分布、微观组织、表面粗糙度,研究讨论了复合工艺对AZ91D镁合金拉伸性能的影响。研究表明:激光冲击强化处理后,镁合金原始晶粒得到明显细化,残余应力达到-122 MPa,表面粗糙度增大,极限抗拉强度提升了15.6%,但塑性下降了27%。激光冲击强化复合超声滚压处理后,残余应力的幅值达到了-197 MPa,表面晶粒得到进一步细化,表面粗糙度大幅改善,材料极限抗拉强度提升了27.4%,材料塑性相对激光冲击强化后提高了19.4%。在残余应力、晶粒细化及粗糙度改善三者的共同作用下,复合工艺延缓了裂纹的扩展速度,显著改善了表面应力状态,提升了镁合金的力学性能。

To investigate the effect of the composite process of laser shock peening(LSP)and ultrasonic surface rolling(USR)on the mechanical properties of AZ91D Mg alloy,the surface of AZ91D magnesium alloy was strengthening treated by Nd:YAG high power laser and USR processing. The tensile test and fracture observation were also carried out. The residual stress distribution,microstructure and surface roughness of the material were analyzed. The effect of the composite process on the tensile properties of AZ91D magnesium alloy was researched and discussed. The results show that after LSP,the original grain of the material is remarkably refined,the residual stress was up to-122 MPa,the roughness became larger,and the ultimate tensile strength of the magnesium alloy was increased by 13.3%,but the plasticity of the material decreased by 27%. After the composite process of LSP and USR,the residual stress was up to-197 MPa,the surface grain was further refined,the surface roughness was greatly improved,the ultimate tensile strength of the material was increased by 18.5%,and the material plasticity was improved by 19.4% compared with LSP sample. Under the common influence of residual stress,grain refinement and roughness improvement,the composite process delayes the crack growth rate,reduces the stress concentration on the surface,and improves the mechanical properties of the magnesium alloy.