An analysis of the microstructure of spark plasma sintered and hot isostatically pressed V4Cr4Ti1.8Y0.4Ti3SiC2 alloy and its thermal stability

The microstructure and thermal stability of V4Cr4Ti1.58Y0.4Ti3SiC2 alloy, fabricated by 60 h mechanical milling of blended powders followed by spark plasma sintering (SPS) and hot isostatic pressing, has been investigated. Analysis was undertaken using orientation image maps obtained from the electron backscattering and transmission Kikuchi diffraction techniques as well as hardness testing. The as-processed microstructure contained a multimodal distribution of grain sizes, in pancaked bands perpendicular to the compression axis of the SPS. This multimodal matrix grain structure exhibited regions of both random and clear 〈111〉 fibre texture with grain boundary disorientations that are virtually all high angle (>15°). Both the pancaking and texture observations are most likely a result of the long hold time of 2 h during SPS. Post processing heat treatment showed the microstructure remained stable up to 1000 °C and significant grain growth was not observed until 1200 °C, suggesting this material has much potential for operation in ultra-extreme environments such as a fusion reactor.