비기저면 집합조직을 가지는 마그네슘 합금의 고속압연 온도 변화에 따른 압연재 미세조직 변화

In this study, the effects of rolling temperature on the microstructural characteristics of a highspeed- rolled Mg alloy with a non-basal texture were investigated. To this end, commercial AZ31 alloy samples in which the basal poles of most grains were tilted at an angle of 45° from the normal direction (ND) to the transverse direction were hot-rolled with a rolling reduction of 80% at a rolling speed of 470 m/min at various temperatures (300 ℃, 350 ℃, and 400 ℃). With increasing rolling temperature, the area fraction of dynamically recrystallized (DRXed) grains increased and the internal strain energy accumulated in the rolled material decreased. This is attributed to the occurrence of homogeneous nucleation throughout the material at higher temperatures. When the rolling temperature increased from 300 ℃ to 350 ℃, the area fraction of coarse unDRXed grains decreased, but the size of the relatively fine DRXed grains increased. Consequently, the average grain size of the rolled material remained nearly unchanged. However, when the rolling temperature increased from 350 ℃ to 400 ℃, the size of the DRXed grains increased considerably owing to enhanced grain growth behavior. This increase led to an increase in the average grain size of the rolled material. The basal poles of the high-speed-rolled materials were mainly tilted 25° - 29° from the ND. This indicates that application of single-pass high-speed rolling causes the non-basal texture of the initial material to transform into a basal texture similar to the typical texture of rolled Mg alloys. (Received April 12, 2019; Accepted June 10, 2019)