Biaxial deformation behavior of AZ31 magnesium alloy at high temperatures

摘要

The evaluation of plastic deformation processing of materials hasbeen based mainly on uniaxial tensile tests. However, for theanalysis of multiaxial stress conditions in sheet-metal plasticforming, more complex tests, such as the controlled biaxial testwith cruciform specimens, are required. In this report, we examinethe relationship between the biaxial deformation behavior andmicrostructure of AZ31 magnesium alloy for initial strain rates of3.0 × 10~(-3) s~(-1) and 2.8 × 10~(-4) s~(-1) at 573 K and 623 K usingcruciform specimens. The results show that the flow stressincreases with decreasing sheet thickness, and the occurrence oftensile twins is confirmed during biaxial tensile deformation at anelongation of 30 % in a cross-section of a specimen under 623 Kfor a strain rate of 2.8 × 10~(-4) s~(-1) . This deformation behavior andevolution of the microstructure is unique in biaxial tensile tests,and is not recognized in uniaxial tensile tests with the sameelongation. Since this controls the width direction of the specimenduring deformation, we can only guess that the plate thicknessdirection can be deformed freely and without restraint. In otherwords, for biaxial tensile test conditions, the transition point of themicrostructure under the influence of the constraint of grainboundary sliding is at 623 K for a strain rate of 2.8×10~(-4) s~(-1).