Synthesis, microstructure and mechanical properties of (Ti,W)_3AlC_2/Al_2O_3 composites by in situ reactive hot pressing

摘要

(Ti,W)_3AlC_2/Al_2O_3 in-situ solid solution composites were successfully synthesized from the elemental powder mixtures of TiC, Ti, Al, and WO_3 using hot-press-aided reaction synthesis. The reaction path was investigated by X-ray diffractometry (XRD), and a possible reaction mechanism was proposed to explain the formation of (Ti,W)_3AlC_2/Al_2O_3 composites in which the thermite reaction between Al and WO_3 formed A1_2O_3 and W, and the latter together with Ti_2AlC and TiC reacted to form (Ti,W)_3AlC_2. The synthesized composites show plate-like grains packed in layer structure typical of Ti_3AlC_2, and the fine A1_2O_3 particles formed in-situ tend to disperse on the matrix grain boundaries. Compared with the monolithic Ti_3AlC_2 synthesized using an identical process, the Vickers hardness, fracture toughness and flexural strength of (Ti_(0.96),W_(0.04))_3AlC_2/5 wt%Al_2O_3 were enhanced by 266.7%, 24.6% and 23.4%, respectively. The mechanisms by which A1_2O_3 increases and solid solution strengthen the hardness, toughness and strength of the material were also discussed.