Mechanical property enhancement of Tip/VW94 composites via the construction of gradient ultrafine-grained structures

A gradient ultrafine-grained structure was successfully fabricated on the surface of 3.5 wt% Ti p /VW94 composites by sliding friction treatment (SFT), and the microstructure and mechanical properties of the material were investigated. The results show that due to the gradient strain, a gradient deformation layer with a thickness of approximately 400 μm is formed on the material's surface. The grain size of the surface layer is refined to 87 nm as a result of severe plastic deformation. During the SFT process, numerous dislocations are activated, and many twins form, facilitating coordinated deformation and promoting grain refinement. Additionally, the strength of the gradient-structured composites is significantly enhanced without a noticeable loss in ductility compared to the initial state. Specifically, the ultimate tensile strength increases from 329 MPa to 383 MPa, while the yield strength rises from 254 MPa to 309 MPa. The presence of Ti particles leads to the formation of a strain misfit field, which hinders dislocation migration and provides energy for twin nucleation, inducing numerous dislocations and twin boundary strengthening. These findings highlight the effectiveness of SFT in optimizing the mechanical properties of Ti-reinforced Mg-based composites.