Synthesis of diamond composites via microwave sintering and the improvement of mechanical properties induced by in-situ decomposition of Ti3AlC2

Metal matrix diamond composites (MMDC) started from the pre-alloyed powders with the addition of different concentration of Ti3AlC2 MAX phase were prepared via microwave assisted sintering (MAS) method. The microstructure of samples was examined by SEM, EDS and XRD characterization methods. The mechanical properties including relative density, abrasive ratio, impact toughness, hardness, elastic modulus and bending strength were also analyzed to investigate the contribution of the additive of Ti3AlC2. The results demonstrate that Ti3AlC2 additive is beneficial for promoting the mechanical properties and the optimized Ti3AlC2 addition concentration is 25 wt %. The enhancement effect of the comprehensive mechanical properties could be due to the in-situ decomposition of Ti3AlC2 induced by diamond and the generated Al to stuff porosity and then conducive to densification of the sintered structure. Simultaneously, Al element reacts with diamond abrasive to produce Al4C3 transition layer on the diamond surface, which improves the bonding force between the diamond and the matrix for the MMDC sample. The advantages of microwave heating and the pre-alloying of raw powder can avoid the graphitization behavior of internal diamond abrasive owning to the relatively low sintering temperature. The potential sintering mechanism of the pre-alloyed diamond composites by the addition of Ti3AlC2 in the microwave field was also discussed.