High Temperature Microstructure Evolution And Deformation Mechanism Of Magnesium Alloy

The purpose of this paper is to investigate the microstructure evolution oftwin-roll casted AZ31alloy and high temperature tensile properties of coarse grainedMg-2Al (wt.%) alloy during the high temperature tensile tests. On one hand placingan emphasis on the understanding of the texture characteristics and law of slip systemstartup, on the other hand the high temperature deformation mechanism and effects ofsolute Al content on deformation mechanism of coarse grained Mg-2Al alloy.Under constant temperature of450°C4, fixed strain texts of AZ31alloy wereconducted under constant tensile rate of10-3s-1. The texture characteristics ofdeformed specimens were investigated by using electron back-scattered diffraction(EBSD). The results show that the degree and volume fraction of dynamicrecrystallization are low under deformation condition of high temperature and lowstrain rate, the grain size increases with increasing the strain. The basal texture stillkeeps stable during the high temperature tensile tests, but the increase of strain isfound to weaken the basal texture and strengthen the anisotropy. It is still found theincrease of lattice orientation rotation and number of the grains that occur large anglerotations. The increase of strain will promote the slip system of pyramidal face tostart.Under constant temperatures of300°C~450°C, elongation-to-failure tests wereconducted under constant tensile rates of10-3s-1and10-2s-1, strain-rate-change testswere conducted under varying strain rates from4.98×10-5~2.02×10-2s-1. The resultsshow that the deformation mechanism of pure Mg under the applied test conditions istypical dislocation climb creep, stress exponent of is n≈5.00. While the elongation ofMg-2Al alloy are higher than100%at400°C and450°C when the tensile rate is10-3s-1, where the stress exponent of n≈3.83and creep activation energy of Q=141.46kJ·mol-1. This is due to add2wt.%Al, the deformation mechanism maybe transformfrom dislocation climb creep to solute drag dislocation creep.