Static recrystallization behavior of the cold-rolled Mg-1Al-1Zn-0.1Ca-0.2Y magnesium alloy sheet

Abstract

In this study, we investigated the static recrystallization behavior and basal texture change from rolling direction (RD)-split (c-axes of grains toward the RD) to transverse direction (TD)-split (c-axes of grains toward the TD) of the cold-rolled Mg-1Al-1Zn-0.1Ca-0.2Y (AZXW1100) alloy during annealing. The cold-rolled AZXW1100 alloy sheet contained highly deformed shear bands (SBs), corresponding to 58 % of the total area, which caused rapid recrystallization at the beginning of annealing. The fine recrystallized grains nucleated in the SBs, and the intersection of the twins grew larger while consuming the deformed matrix grains, which did not recrystallize even at the late stage of annealing and were consumed by the surrounding recrystallized grains nucleated on the SBs. Owing to the difference in the recrystallization initiation time between the SB and deformed matrix grains, the recrystallized grains nucleated in the SBs guided the overall recrystallization behavior. Additionally, quasi-in-situ electron backscattered diffraction analyses clearly showed that among the recrystallized grains nucleated at the SBs, the grains with TD texture components became larger through preferential growth, whereas those with RD texture components did not grow and disappeared. Owing to this preferential grain growth, the texture intensity in the RD decreased and that in the TD was maintained, resulting in the formation of a diamond-like or TD-split texture. In this study, the co-segregation of Al, Zn, and Ca atoms along the grain boundaries and the formation of nanoscale Al8Mn5 particles were found to reduce boundary mobility and, consequently, hinder grain growth. These results can explain the texture change from a strong RD-split to a weak TD-split during annealing.