Effect of α-SiC on the microstructure and toughening of hot-pressed SiC-AlN solid solutions

Abstract

The Effect of α-SiC on the microstructure and toughening ofSiC-AlN solid solutions from powder mixtures of β-SiC and AlNby hot-pressing were studied in the 1870 to 2030°Ctemperature range. The reaction of AlN and β-SiC(3C) powderscausing transformation to the 2H(wurtzite) structure appeared todepend on hot-pressing temperatures and an additive of α-SiC.For the composition of 49 wt% AlN/49 wt% SiC with 2 wt%α-SiC and 47.5 wt% AlN/47.5 wt% SiC with 5 wt%α-SiC at 2030°C for 1 h, the complete solid solutionswith a single phase of 2H could be obtained. The appreciable amountof α-SiC could develop the columnar inter-grains of 4H phaseand the stable 2H phase with the relatively uniform composition andgrain size distributions. The effect of α-SiC on the phasespresent and compositional microstructures with columnar inter-grainswas investigated using X-ray diffraction, scanning electronmicroscopy and transmission electron microscopy. The fracturetoughness and Vickers hardness of the hot-pressed solid solutionswere examined by the indentation-fracture-test method.