Comparative Study On Deformation Property Of Magnesium Alloy Sheet At Laser Shock Forming And Stamping Forming Conditions

It is well known that magnesium alloys are the lightest metallic structural materials and has been, hence, widely used in the aerospace, electronics, and automobile industry. However, magnesium alloys rolling sheet exhibits strong deformation resistance, intensity anisotropy due to basal or near-basal textures for rolling. Besides it only possess two independent easy slip systems at ambient temperatures that fails to satisfy the Taylor Criterion which requires five independent easy slip systems for homogeneous generalized ductility of a polycrystalline aggregate. So hot forming is common for magnesium alloys rolling sheet’s plastic forming in practice. But the hot forming such as stamping needs a mass of heat-resistant die & mould, which greatly increase the development cycles and manufacturing cost of magnesium products. While laser shock forming (LSF) is a novel plastic forming technique that has many advantages, as high forming pressure, high strain rate and requires no dies, than traditional methods, so it is especially suitable for the forming of sheet metal, which has strong deformation resistance and exhibits poor formability at ambient temperatures. Based on the deformation features of magnesium alloy and deficiencies of traditional forming methods, the deformation property and anisotropic characters of magnesium alloy are compared between laser shock forming and stamping forming. The followings are the main contents and results of this paper:1) The hot drawing property of AZ31 was investigated through experiment and simulation. The results indicated that the limit drawing deepth increases in a nonlinear way with the increasing of temperature and reached the maximum deepth at 200℃, but decreased after 200℃. so the higher temperature is not better to deformation.2) The relationship between laser shock forming parameters, such as pulse energy and shock times, and the formabality of AZ31 sheet was researched. The results shows that the forming depth of AZ31 sheet increases in a nonlinear way with the increasing of pulse energy and shock times, but oversized energy will make the sheet fractured too earlier to exploit the metal forming performance fully and too many shock times will increase the hardening effect, It is evident that pulse energy and shock times must be comprehensively considered to obtain greater deformation.3) The fracture modes of AZ31 sheet was comparative studied at laser shock forming and stamping forming conditions. Result shows that the failure behaviour of AZ31 under laser shock forming condition, whose rupture is a dynamic process along with multiple directivity crack expanding and spalling, is very different to that of stamping forming condition.4) The anisotropic behavior of AZ31 sheet was comparative investigated under laser shock forming and stamping forming conditions, it was founded that laser shock forming can reduce the anisotropic characteristic of magnesium alloy sheet at lower temperatures. The anisotropic characteristics of AZ31 sheet that under the condition of laser shock forming is weaker than that of stamping forming condition, and the anisotropic characteristic decrease in a nonlinear way with the increasing of temperature and reduced to the minimum at 200℃, but increased after 200℃and exceeded the that under stamping forming condition after 240℃, Yet, the anisotropic characteristics decrease in a nonlinear way with the increasing of temperature under the stamping forming condition.