Effect of temperature on stretchability of anisotropic AZ31 magnesium alloy sheet

摘要

This paper deals with effect of temperature on stretchability of anisotropic AZ31(Mg-3%Al-l%Zn) magnesium alloy sheet. Results of stretching process test are compared with those of tensile test. The sheet has an anisotropic character for angle to hot-extrusion direction(Φ=0°, 45°, and 90°). Here, Φ=0° means a direction of extrusion. Tensile specimens cut down to three directions of Φ=0°, 45°, and 90° are a shape of 14mm in elongation, 3mm in width and 0.44mm in thickness. Test piece for investigating the limiting stretching stroke is a sheet of side length 90mm and 0.44mm in thickness. For the stretching process test, the punch head is a hemispheric shape of 20mm in diameter and the die is a cylindrical shape of 27mm in inside diameter. Both tension and stretching process tests were performed at four kinds of test temperature(T=293, 393, 473, and 573K) in a thermostatic chamber and at a crosshead speed(v) of 5 mm/min using an Instron-type testing machine. Comparing the limiting stretching stroke determined by the stretching test with elongation, rvalue, and n-value obtained by the tensile test, it is confirmed that the limiting stretching stroke is qualitatively related to the elongation and r-value, and not to n-value.