TEXTURE OF MAGNESIUM ALLOY SHEETS HEAVILY ROLLED BY HIGH SPEED WARM ROLLING

摘要

Magnesium alloy sheets had to be rolled at elevated temperatures to avoid cracking. The poor workability of magnesium alloy is ascribed to its hcp crystallography and insufficient activation of independent slip systems.Present authors have succeeded in one-pass large draught rolling of AZ31 and ZK60A magnesium alloy sheet below 200 °C by raising rolling speed above 1000m/min. Heavy reduction larger than 50 % can be applied by one-pass high speed rolling even at room temperature. The improvement of workability at lower rolling temperature is due to adiabatic temperature rise of a material during rolling by plastic working. The texture of heavily rolled magnesium alloy sheet is investigated in the present study.The texture of AZ31B sheet rolled 60 % at room temperature was <0001>//ND basal texture. At the rolling temperature above 100 °C, the peak of (0001) pole tilted 10-15 degrees along RD direction around TD axis to form a double peak texture. The texture varied through the thickness. At the surface, the (0001) peak tilted 10-15 deg along TD direction around RD axis. The direction of (0001) peak splitting rotated 90 degrees from the surface to the center of thickness. The texture of heavily rolled ZK60A sheets is almost similar to that of AZ31B sheets. Heavily rolled magnesium alloy sheets have non-basal texture. The sheets having non-basal texture are expected to show better ductility than sheets with basal texture.