Microstructure and phase stability of TiVTa-based low-activation, multi- principal-element alloys

Abstract

One of the key problems restricting the commercial application of controllable nuclear fusion reactors is plasma facing materials (PFMs). As the most promising PFMs, there are still many problems in the applications of tungsten and tungsten alloys. Due to their high strength at elevated temperatures, high melting point and good irradiation resistance, refractory multi-principal-element alloys are expected to meet the needs of PFMs. In the present study, (TiVTa)95X5(X=Cr, Zr, W) was designed and manufactured by using arc-melting. The effects of the addition of Cr, Zr and W on the microstructure and phase stability at 900 ℃ of TiVTa-based alloys were investigated by XRD, SEM and EDS. The results show that as-cast TiVTa-based alloys are simple solid solutions with BCC structure. After homogenization treatment at 1200 ℃, phase decomposition occurs in the (TiVTa)95Cr5 alloy, and a small amount of second phase C15_Laves appears in the matrix. At 900 ℃, TiVTa-based alloys are all decomposed into a BCC main phase and a C15_Laves second phase which mainly distributed along the grain boundaries, and the volume fraction of the second phase in TiVTa and (TiVTa)95W5 alloys is small whereas the addition of Cr and Zr intensifies the phase decomposition. After phase structure and elemental analysis, the lattice constant and elemental composition of the precipitated C15_Laves phases in (TiVTa)95X5(X=Cr, Zr, W) alloys are inconsistent with the possible Laves phase in the binary alloy system, and the difference is mainly attributed to the elemental composition of the Laves phase.

Keywords

• tivta
• low activation refractory alloys
• multi-principal element alloys
• phase stability