冷喷涂镁合金基体残余应力的数值研究

Numerical Study on Residual Stress of Cold Sprayed Mg-alloy Substrate

目的研究冷喷涂Mg-alloy基体过程残余应力的变化趋势。方法采用ABAQUS/Explicit有限元分析软件,以AZ31作为基体材料、Al-7075作为颗粒材料进行碰撞模拟,并添加无限元素层以增强数值稳定性,同时考虑多颗粒沉积对颗粒沉积基体时产生的残余应力的影响。结果经有限元模拟,颗粒的残余应力随着冲击速度的增加,呈现先增大后减小,最后逐渐增大的趋势。应力分布相对于中心轴对称,同时产生明显的金属射流现象。改变入射角后发现,当沉积速度为800m/s、入射角度为90°时,颗粒残余应力达到最大,为-2742.72 MPa,但在结合过程中,基体残余应力的变化相对颗粒较为稳定。通过对多颗粒沉积的研究发现,颗粒2在23 ns左右沉积到颗粒1后,将颗粒1的最小残余应力从-1577.66 MPa松弛到-1099.06 MPa;颗粒3在53 ns左右沉积到颗粒2后,颗粒3的最小残余应力为-1152 MPa,与颗粒2相差不大。后续颗粒也将遵循该规律。结论单颗粒沉积时,瞬态喷丸过程残余应力的变化较为剧烈,热冷却过程中趋于稳定,对残余应力的进一步缓解影响不大。多颗粒沉积时,后一颗粒对前一颗粒起到松弛作用,同时也能起到夯实作用,增强涂层的结合强度,有利于形成较好的涂层。

ABAQUS/Explicit finite element analysis software was used to study the change trend of residual stress in the process of cold spraying Mg-alloy substrate.With AZ31 as the substrate material and Al-7075 as the particulate material for collision simulation,and an infinite element layer is added to enhance numerical stability,taking into account the effect of multi-particle deposition on the residual stress of the particle deposit substrate.By finite element simulation,the residual stress of the particles increases and decreases with the increase of impact velocity,and finally gradually increases.The stress distribution is symmetrical relative to the center axis,and obvious metal jet phenomenon occurs,and it is found that when the sedimentation velocity is 800 m/s and the incident angle is 90 degrees after incident angle changes,the particle residual stress is maximized,i.e.−2742.72 MPa,but the change of residual stress of the substrate is relatively stable compared to that of the particles during the binding process.Through the study of multi-particle deposition,it is found that after the particle 2 is deposited to particle 1 in about 23 ns,the minimum residual stress of particle 1 is relaxed from−1577.66 MPa to−1099.06 MPa.When particle 3 is deposited to particle 2 in about 53 ns,the minimum residual stress of particle 3−1152 MPa,which is not much different from that of particle 2.Subsequent particles will also follow this rule.And it is concluded that when a single particle is deposited,the change of the residual stress in the transient shot peening process is relatively severe,and it tends to be stable during the thermal cooling process,which has little effect on the further relief of the residual stress.When multiple particles are deposited,the latter particle can relax the former particle,and at the same time,it can also play a role of compaction,enhance the bonding strength of the coating,and help to form a better coating.