Microstructure induced duplex Hall-Petch effect and its strengthening/ toughening mechanisms in SiC@TC4 composites prepared by spark plasma sintering

Microstructure induced duplex Hall-Petch effect and its strengthening/toughening mechanisms in SiC@TC4 composites prepared by spark plasma sintering were systematically investigated in the current study. The microstructure characterization demonstrated that SiC additions significantly tailored the microstructure of SiC@TC4 composites. The SiC additions distinctly refined the grain size of SiC@TC4 composites. Increasing SiC addition also changed the microstructure of SiC@TC4 composites from the Widmansta center dot tten type to the duplex type. Large SiC addition almost inhibited the formation of continuous alpha GB phase in SiC@TC4 composites. The growth of alpha phase was promoted due to the energy storage effect inside the TC4 alloy powders during the sintering process. SiC addition distinctly improved the tensile strength while seriously deteriorating the plasticity of SiC@TC4 composites compared to that of TC4 alloy. However, SiC@TC4 composites with various SiC additions exhibited the similar plasticity. SiC additions also resulted in different tribological properties of SiC@TC4 composites. The TC4-0.1SiC exhibited the worse tribological properties than that of TC4 alloy due to the softened matrix and low SiC addition. TC4-0.3SiC and TC4-0.5SiC composites exhibited the more excellent tribological properties due to the more SiC addition. A duplex Hall-Petch model was proposed to evaluate the multiple strengthening and toughening mechanisms in the SiC@TC4 composites.