Effect of temperature on deformation mechanisms of the Mg88Co5Y7 alloy during hot compression

Highlights: • The Mg₈₈Co₅Y₇ (at. %) alloy show high compression stress at hot compression. • The microstructural evolution and deformation mechanisms are characterized by transmission electron microscopy. • The grain boundary pinning effect is important for the relatively high strength. -- Abstract: The deformation mechanisms and microstructure evolution of Mg₈₈Co₅Y₇ (at.%) alloy with long period stacking ordered (LPSO) phase during compression at 373–673 K have been studied using transmission electron microscopy. The alloy consists of α-Mg matrix, interdendritic LPSO phase, and other Mg-Co-Y intermetallic compounds. Increasing temperature leads to a general decrease in strength of the Mg₈₈Co₅Y₇ alloy. A large number of {10$\overline{1}2$} tension twins and deformation bands are activated in the matrix, whereas basal slip and deformation kink dominate in the LPSO structures during compression at 373 and 473 K. Non-basal slip in matrix and almost no dynamic recrystallization are responsible for high strength and the good ductility of sample deformed at 573 K. Recrystallization of Mg matrix occurs upon deformation at 673 K, dramatically lowering the corresponding strength. Further, the grain boundary pinning effect from LPSO phase, MgYCo₄ phase, and broken Mg₃(Co, Y) segments is supposed to account for the relatively high strength of Mg₈₈Co₅Y₇ alloy at high temperatures.