A Study On Deformed Process And Mechanism For Improving Plasticity Of AZ31Magnesium Alloy

Magnesium alloy is a lightweight structural material which has a boomingindustrial application for its high specific strength and stiffness, great electromagneticshielding and damping performance and facility for recycling. However, its HCPcrystalline structure causes limited independent slip systems leading to a poorformability. The as-extruded AZ31is a potential wrought magnesium alloy having awidely use, but its mechanical anisotropy result from strong basal texture severelyrestrict its plasticity. The purpose of this paper is to study improving the plasticity ofmagnesium alloy by means of modifying the deformed process and parameters.In first part of this study, a novel process with annealing treatment followed acertain pre-strain is proposed, and the effects of the process parameters on the plasticityof AZ31has been investigated. Evident plastic improvement observed after a pre-strainof8.6%followed by annealing at300℃for30min. The microstructure and textureobservation shows that twins and a change of basal texture by pre-strain, and twinsdisappeared after annealing treatment which increases the plasticity by dismissing theobstacle to deformation.The second part of this study examines the compressive plasticity of AZ31magnesium alloy loaded perpendicular and parallel to the extruded direction(ED).Result shows that maximum compressive rate perpendicular to ED is higher than thatparallel to ED deformed no more than150℃but reverse above200℃, and it can beexplained by theory of interaction between twins and dislocations.The last part studies the effects of deformed process parameters includingtemperature and strain rate on tensile plasticity of AZ31magnesium alloy. It indicatesthat the elongation increases with the decreased strain rate from10-2s-1to10-4s-1andraised temperature no more than400℃, and an obvious increase happens whendeformed above350℃which involves in non basal slips and dynamic recrystallization.However, the elongation drops when tested at450℃with the strain rate of10-4s-1, which can be analyzed by cavities developed from superplastically deform causes thefacture of magnesium alloy.