Dynamic recrystallization in nanocrystalline AZ31 Mg-alloy

A nanocrystalline surface layer of AZ31 Mg alloy was fabricated successfully by sliding friction treatment. The microstructure was characterized by a transmission electron microscopy (TEM). In the process of plastic strain-induced grain refinement, the nucleation and growth of new grains as well as grain split are all observed. These experimental phenomena indicate that discontinuous dynamic recrystallization (dDRX) and continuous dynamic recrystallization (cDRX) are responsible for grain refinement of Mg nanocrystallites. Further analysis reveals that stored strain energy (SSE) plays a critical role in the grain refinement mechanisms (dDRX or cDRX): high SSE facilitates dDRX and low SSE conduces to cDRX.