Microstructural analysis of segregated area in twin roll cast magnesium alloy sheet

Abstract

Twin roll casting process of magnesium alloy has been studied by various institutes since POSTECH started at the world first time. RIST has done the research and development program of twin roll casting and reverse warm milling of magnesium alloy sheet with 600 mm width. Presently, RlST is working on twin roll casting program of magnesium alloy sheet with 2,000 mm width. Twin roll cast magnesium alloy sheet includes segregated area which is important due to controllable quality of final product. Here we present the microstructural analysis of segregated area in twin roll cast magnesium alloy sheet to understand segregation phenomena. Especially, we studied on phase identification in segregated area, comparing the theoretically calculated simulation. Scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry were used for the phase identification. Our result shows that two kinds of segregation morphologies are observed in the segregated area, not depending upon the location in the sheet. Phase identification shows that segregated area includes densely continuous or dispersed beta and phi phase, and dispersed Al8Mn5 and Mg2Si.