Formation mechanism of TiC-Al2O3 ceramic reinforcements and the influence on the property of ZL101 composites

In this paper, Al2O3-TiC/ZL101 composites were fabricated via in-situ reaction process with TiO2, Al, graphite and ZL101 powders. Microstructure characteristics, formation mechanism of reinforcements, thermodynamic calculation of reaction, hardness and tribological behavior of the composites were investigated in detail. The distribution of Al2O3 and TiC precipitates changes from agglomerate to relative uniform with the content rise of strengthening phases. Al2O3 precipitates are irregular spherical with the average size of 3-5 mu m. The shape of TiC particles is cube or polygon and the size is about 2-4 mu m. The thermodynamic calculation of reactants further proves the reinforcements formation, which is consistent with the microstructure observation and X-ray diffraction result. The formation mechanism of TiC and Al2O3 mainly is by diffusion and precipitation. The microhardness and wear performance of composites remarkably improve, friction coefficient and wear weitgh loss decrease with the content rise of TiC and Al2O3 phases. The microhardness of C3 composite increases from 93HV to 162HV, the friction coefficient (FC) and weight loss decrease from 1.15 and 0.128g to 0.43 and 0.066g compared with the ZL101 alloy. C3 composite has the best wear property for the highest hardness, the lowest FC and weight loss. Microstructure refinement, uniform dispersion of TiC and Al2O3 precipitates and the strong interfacial adhesion between reinforcements and matrix are attributed to the better wear performance of composites. The wear surface morphology shows that the wear mechanism of ZL101 alloy is mainly adhesive wear while the wear style of the composites is abrasive wear.