Mechanical Behavior And Thermal Stability Of Mg Alloy

The present study mainly uses the AZ31,AZ80 hot rolled plate and AZ31 extruded rods,preparing different twinning structures via different pre-deformation methods(multi-pass compression and single-pass compression).The mechanical properties and thermal stability are tested.Besides,the evolution of microstructure during annealing treatment are analyzed by EBSD,SEM and optical graph methods.The main results are as bellow:(1)Small twin structure in AZ31 alloy can be prepared by 6 Pass multi-compression method,the deformation mode has influence on the mechanical properties and precompressed samples.Both compression mode(3.5% each pass,3.5% and 7% alternative)can dramatically increase the tension and compression strength of AZ31 alloy,and the tense-compression yield anisotropy are improved.The 3.5% and 7% alternative deformation method has better improvement effect on mechanical properties.This twin structure is basically stable under 100 ?C,and the mechanical properties are same as the unannealed samples.However,this twin structure can be removed in annealing at 200 ?C for 2 hours,causes the drop on tension and compression strength and increase on tense-compression yield anisotropy.(2)12 Passes Multi-compression and aging treatment method can dramatically increase the tension and compression strength of AZ80 alloy,and the tense-compression yield anisotropy are improved.A lot of small twin structure are formed after solution treatment and 12 passes compression,the twin structure changed the shape and the distribution of second phase during aging treatment.(3)Extension twins are thermally unstable during annealing at 250? C,and annealing at higher temperature can increase the thermal mobility and longer annealing time also can reduce the amount of twin.Refining the initial grain size from 32 to 15 mm does not reduce the thermal stability of twins.A pre-annealing at 200 ?C for 6 hours can't increase the thermal stability at higher temperature effectively.During annealing treatment,both the consumption of twins by matrix and that of matrix by twins happen.Thus,annealing treatment hardly changes the texture components.