변형속도에 따른 M1 마그네슘 합금의 고온변형 중 미세조직 형성 거동

Abstract

Because of low density and high specific strength, Magnesium alloys have been paid an attention in various fields such as the automobile industry. However, AZ system magnesium alloy shows poor creep resistance during high-temperature and constant stress needed in power transmission device occupied quarter of weight of car. Many researchers were found that creep resistance is improved by containing manganese on magnesium so called; M1 magnesium alloy which can be a suitable solid-solution alloy. Despite these advantages, there still remains a problem that the hcp crystal structure alloys formed a strong basal texture during high temperature deformation, which makes hard to subsequent deformation and affects mechanical property. It is generally known that the basal texture is formed by dynamic recrystallization, but there seem no studies on the microstructural development during high-temperature on the M1 magnesium alloy. In this study, microstructure evolution and crystallographic orientation are investigated under various deformation conditions in M1 magnesium alloy. M1 magnesium ingot was rolled at 673 K with a rolling reduction of 30 %. The compression tests specimens were fabricated with the compression plane of the specimens are parallel to the rolling plane, and then the specimens were annealed at 823 K for 1h. Uniaxial compression tests were conducted at 723 K and under a strain rate ranging from 5.0x10-4 s-1 to 5.0x10-2 s-1 up to a true strain of –1.0. For observation of crystal orientation distribution, EBSD measurement was performed. Occurrence of the dynamic recrystallization and grain boundary migration were confirmed in all case of the specimens. The distribution of the grains is not uniformed in the experimental conditions.