Effect Of Torsion Deformation And Heat Treatment On Mechanical Properties And Microstructural Evolution Of Mg Alloy

Improving the strength and formability of magnesium alloys via pre-deformation is an important issue in magnesium research.Torsion deformation is an effective and simple technique to tailor the mechanical properties of Mg alloys.In this study,the influences of torsion route on microstructure and mechanical properties of AZ31 and AZ91 rods were investigated.Precipitation behavior was analyzed systematically.The different microstructure and precipitation behaviors in the various regions of the torsion sample were explainedThe results can be summarized as follows:①Torsion deformation can introduce dislocations and {10-12} twin and the basal pole of texture tends to rotate towards ED direction.From center to edge positions,both dislocations and {10-12} twin area fraction gradually increase due to the increase of torsion equal strain.②Both route TA and TB torsion can introduce a large number of dislocations to harden the active deformation modes.However they cause different textural evolution.Route TA torsion is more effective for the enhancement of compressive yield strength and the improvement of yield asymmetry,while route TB torsion is more effective for the enhancement of tensile yield strength.③Twin structures are favorable nucleation sites for continuous precipitation.The precipitation behavior of un-twinned regions largely depends on the local strain.High strain can generate a mass of dislocations and thus promote continuous precipitation in un-twinned regions.In the sample,gradient precipitation characteristics were observed due to the gradient distribution of twins and dislocations.④As-received sample exhibits a large tension-compression yield asymmetry.Aging treatment can enhance the tensile and compressive yield strength simultaneously and reduce the yield asymmetry.