AZ31B Mg합금의 재결정거동에 미치는 가공열처리의 영향

Abstract

The effects of reduction rate and annealing temperature on the recrystallization behavior have been investigated in hot-rolled AZ31B Mg alloy sheet. In addition, the influence of annealing temperature on the strain anneal and grain growth, texture development and tensile The results obtained are as follows: (1) Deformation bands were formed within grains after hot-rolling and the amount of them increased with increasing reduction rate. Recrystallization grains were observed at deformation bands by discontinuous dynamic recrystallization. (2) Recrystallization rate increased with increasing reduction rate in thickness even at same annealing temperature and recrystallization completed at 230 ℃. Recrystallization behavior could be detected by DSC(Differential Scanning Calorimeter) measurement, and heat flow for recrystallization increased with increasing recrystallization rate. (3) Abnormal grain growth occurred by annealing at 250 ℃ irrespective of the amount of deformation. In addition, grain growth rate became larger with increasing strain owing to grain growth by rotation and collapse of grains. (4) Basal texture i.e. (0001)±5°[210] is developed in a commercial AZ31B Mg sheet, and the texture is not changed considerably by annealing over 400 ℃×30min, while (100) component with high intensity can be observed due to abnormal grain growth. (5) When the sheet is tensile-deformed with RD, 45° and TD directions at room temperature, fracture strains are given by 25.8, 21.4 and 11.9 % in the order of RD, 45° and TD directions, respectively. (6) The maximum tensile strain of around 25 % is obtained by annealing below 300 ℃×30min, but it is abruptly decreased to 16 % by annealing above 400 ℃×30min owing to intergranular fracture of abnormal grown grains.