Residual stress induced by cold spray coating of magnesium AZ31B extrusion

Abstract

Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold spray technology. Cold spray high impact velocity of particles colliding with the substrate induced beneficial compressive residual stresses. Magnitude of the residual stress at the surface and its distribution through the thickness were measured using X-ray diffraction. With particle spraying velocity of 400m/s, the residual stress was measured to be −25MPa at the surface. The process of collision and development of residual stress was then modeled using LS-DYNA software to study the effect of the cold spray process parameters on the residual stress profile. Various models were employed to simulate the impact of the single and multiple particles. An asymmetric material model that considers the strain rate effect was employed to model AZ31B different behavior in tension and compression. Results of simulations for impact of multiple particles were compared with the results of XRD measurements on the substrate surface and through the depth of the substrate. After the validation of the models, a parametric study was performed on the impact of a single particle to find the optimum cold spray particle velocity, size, shape, incident angle, and friction parameters. Parameters leading to the optimum residual stress profile are introduced herein.