Microstructures and mechanical properties of the novel CuCrZrFeTiY alloy for fusion reactor

Abstract

Cu–Cr–Zr alloy has been widely considered to be used as heat sink materials in the fusion reactor due to its superior properties. However, Cu–Cr–Zr alloy suffers significant creep deformation and softening as the temperatures is above 300–400 °C. Advanced Cu alloys with high strength, high conductivity and high thermal stability need to be developed to meet the requirements in the future fusion reactor. In this work, a novel Cu–Cr–Zr–Fe–Ti–Y alloy was designed and prepared by vacuum induction melting, followed by homogenization treatment, hot-rolled, solid solution, cold-rolled and aging treatments. Tensile properties, hardness and electrical conductivity of the alloys aging at different temperatures were tested. The alloy aged at 500 °C exhibits excellent tensile strength up to 541 MPa and high electrical conductivity of 82% IACS. The alloy maintains high tensile strength even annealing at 500 °C for 72 h. The microstructures of the alloy were characterized by optical, scanning and transmission electron microscopy, and it is found that the high thermal stability of the novel alloy is mainly contributed to two reasons. One is the high friction of low-ΣCSL grain boundaries (mainly Σ3) with low energy detected in the matrix, which are difficult to slid and have higher thermal stability than general high-angle grain boundaries. Another one is the two kinds of high-density precipitates detected in the matrix. The larger Cr1·4Fe particles are semi-coherent with the matrix, and the orientation relationship is [011]Cu//[011]Cr1·4Fe, (100)Cu//(011‾)Cr1·4Fe and (111‾)Cu//(2‾11‾)Cr1·4Fe. The smaller Cr particles are coherent with the matrix, and the orientation relationship is [011]Cu//[1‾11]Cr, (100)Cu//(011‾)Cr and (01‾1)Cu//(211)Cr. The strengthening mechanism of the alloy was analyzed in details, and the calculation yield strength (480 MPa) is well coincident with the experimental value (473 MPa).