Clarifying interfacial microstructures of Ti particle reinforced Mg-Zn-Mn composites to achieve good strength-ductility synergy

In the field of particle reinforced magnesium (Mg) matrix composites (MMCs), the interfacial microstructures between reinforcements and Mg matrix are a subject of interest for most researchers. In this work, the 2 wt.% Ti particle reinforced Mg-6Zn alloy composites with different contents (0, 0.5, 1, 1.5, 2 wt.%) of Mn were prepared using semi-solid stirring assisted ultrasonic treatment followed by hot extrusion. With the increment of Mn element, the characteristics of mixed-grain structure became obvious and the DRX was inhibited. Meanwhile, the interfacial product gradually changed from MgZn₂ to Mn₂Ti. The tensile test demonstrated that the 2Ti/Mg-6Zn-1.5Mn composite exhibited an excellent strength-ductility synergy, achieving the highest yield stress (YS), ultimate tensile stress (UTS) of 239 MPa, 366 MPa, respectively, along with a notable elongation (El.) of 20.6%. The increased strength is mainly due to the grain refinement, the precipitation strengthening, the HDI strengthening and the strong interfacial bonding including the tightly Ti/Mn₂Ti bonding and the Mn₂Ti/Mg coherent orientation relationship. The ideal El. is the result of fine/coarse bimodal structure and the proper interfacial reaction, which can reduce the occurrence of cracks.