Immiscible Fe-Mg system diffusion mechanism induced by dynamic recrystallization at the steel/Mg warm rolling interface

Steel/Mg laminate composites were prepared by a warm rolling composite process in this work. The structural characteristics and elemental distribution of the steel/Mg composite interface region were characterized by SEM, EBSD, and TEM. The formation mechanism of interfacial structure and the diffusion mechanism of interfacial elements were analyzed. Finally, the interfacial bonding mechanism of steel/Mg laminate composites was revealed. The results showed that the steel and Mg in the interface region underwent continuous dynamic recrystallization and discontinuous dynamic recrystallization, respectively. This resulted in a gradient distribution of nanoscale steel grains and a uniform distribution of micron-sized Mg grains. There were oxygen-rich bonding region and oxygen-poor bonding region at the steel/Mg warm-rolled composite interface. In the oxygen-poor bonding region, mixing of the immiscible Fe-Mg system occurred, forming an Fe-based supersaturated solid solution. The difference in dynamic recrystallization mechanism leads to the deformation storage energy of the steel being about 24 times that of the Mg. Driven by the difference in deformation energy storage between steel and Mg, Mg atoms diffused to the steel side and resulted in the Fe-based supersaturated solid solution. This study provides a new thought for preparing immiscible metal laminate composites.