Microstructure and mechanical properties of low-cost Nb521 alloy fabricated by hot isostatic pressing

Low-cost Nb521 alloy (Nb-5W-2Mo-1Zr) was fabricated by hot isostatic pressing (HIP) at four temperatures (1220°C, 1300°C, 1380°C, and 1460°C) using waste niobium alloys as raw materials. The specific source of waste niobium alloy is niobium alloy scraps produced by machining NbW5–2 alloy. Microstructure and mechanical properties of the low-cost Nb521 alloy were investigated. The results demonstrated that the matrix of Nb521 alloy is mainly composed of α-Nb, and a small number of precipitates such as ZrO and ZrO 2 can be observed. The bimodal grain size phenomenon was observed in the low-cost Nb521 alloy, which played a major role in the strengthening of the alloy. As the HIP temperature increased from 1220°C to 1460°C, the average grain size of low-cost Nb521 alloy coarsened from 5.1 μm to 9.6 μm. Low-grade prior particle boundaries (PPBs), enriched in Zr and O, were identified, which significantly reduces plasticity, leading to a brittle fracture mode. The room-temperature tensile strength and elongation of low-cost Nb521 alloy exceed 510 MPa and 15 %, respectively. The mechanical properties of low-cost Nb521 alloy reach the requirements of use, which means the purpose of recycling niobium resources has been successfully achieved.