ANALYSIS OF THE STATIC RECRYSTALLIZATION AT TENSION TWINS IN AZ31 MAGNESIUM ALLOY

Abstract

Due to the poor plasticity of magnesium alloys at room temperature(about 15%), twinning plays an important role in the deformation of magnesium alloys,and twins will be the dominant recrystallization nucleation sites.There are at least two types of twinning in magnesium:the {10(?)2}-type tension twinning and the {10(?)1}-type compression twinning.Tension twinning proceeds much more easily than compression twinning since its volume fraction is much higher than that of compression twins,which may have a promotion effect on the recrystallization to a certain degree. Based on the previous research on the static recrystallization at compression twins,the evolution of microstructure and texture in AZ31 magnesium alloy during its static recystallization at tension twins was futher investigated;and the orientational characteristics of new grains formed at tension twins in the early stage of static recrystallization were analyzed by EBSD technique.The results showed that tension twins played only a subordinate role in recrystallization nucleation and suppressed recrystallization rate,thus failed to refine grain size effectively.The strong basal texture was retained and weakened with no new texture component being detected during annealing.New grains were observed to nucleate preferentially at the intersections of tension twin variants or the intersections between tension twins and compression twins.Their orientations were relative random and are strongly scattered from those of original tension twins or compression twins.A comparison of the recrystallization at tension twins and compression twins was made.