Preparation And Properties Of Magnesium Alloy (AZ31) Based On Severe Plastic Deformation

Magnesium alloy had many good characterizations such as light quality and excellent electro-magnetic performance etc,which make them potentially suitable promising candidates for application in automobile parts,electronic products and aerospace.But their strength and ductility was low,which limited their application.This dissertation aimed to find an approach to improve effectively strength and ductility of magnesium alloy and indicate the involved mechanisms.The research contents and obtained results were summarized as follows.Using Magnesium alloy(AZ31) as experimental materials,a technology route for preparing magnesium alloy with high strength and high ductility was studied and successfully developed,with grain size in 1～3μm.This route consisted of solid-solution,large plastic deformation(compressing deformation) and post-deformation heat treatment.It was found that large plastic deformation can increase dislocation and improve strength considerably(yield strength～330MPa),subsequent aging heat treatment can enhance the strength further(yield strength～370MPa) by aging precipitation strengthen mechanism,while the recrystallization heat treatment can lead to a much higher ductility and similar strength in term of magnesium alloy staying at solid-solution treatment state.There was high density of twinning in large plastic deformed(LPDed) magnesium alloy.Using solid-solutionized magnesium alloy,LPDed magnesium alloy, LPDed plus aged magnesium alloy and LPDed plus recrystallized magnesium alloy as experimental materials,tensile deformation mechanism of magnesium alloy was studied.It was found that the tensile deformation mechanisms were strongly dependent on initial microstructure of magnesium alloy.The solid-solutionized conventional magnesium alloy was deformed primarily by twinning mechanism.The LPDed magnesium alloy and LPDed plus aged magnesium alloy was deformed by dislocation mechanism.The LPDed plus recrystallized magnesium alloy was deformed by dislocation mechanism along with grain boundary sliding.Equal-channel angular pressing(ECAP) of magnesium alloy(AZ31) was studied.It was found that the conventional magnesium alloy(AZ31) can not be processed by ECAP need a pretreatment such as thermal compressive deformation.With increasing in the temperature of ECAP,magnesium alloy (AZ31) grain grew.There are few reports relating to the contents of this dissertation at home and abroad.The present results will provide a basis for preparing high-strength and high ductility of magnesium alloy preparation and indicating deformation mechanism of magnesium alloy.