Microstructures and properties of equiatomic CuZr and CuZrAlTiNi bulk alloys fabricated by mechanical alloying and spark plasma sintering

Equiatomic CuZr and CuZrAlTiNi bulk alloys were designed and fabricated by mechanical (MA) alloying and spark plasma sintering (SPS). The results show that during the MA process, the phases of as-milled samples transform from solid solutions to amorphous phases with increasing milling time. Moreover, the as-milled CuZrAlTiNi amorphous high entropy powders possess higher thermal stability and smaller particle sizes than the as-obtained CuZr powders. After SPS, the bulk CuZrAlTiNi samples are comprised of three solid solutions and a AlNi2Zr phase, and have good phase stability. The CuZrAlTiNi sample sintered at 950 °C shows the higher microhardness value of 1007 HV0.2 due to the fine precipitates, the existence of AlNi2Zr phase and solid solution strengthening. In addition, the chemical corrosion behavior of the as-sintered samples has been investigated in the seawater solution. The 950 °C-sintered CuZrAlTiNi sample exhibits excellent passivity and higher pitting resistance as compared to other sintered samples. All the CuZr and CuZrAlTiNi bulk samples show better corrosion resistance than 304 stainless steel revealed by the reduced corrosion rate.