The Structure and Mechanical Properties of the Ti–18Zr–15Nb Alloy Subjected to Equal Channel Angular Pressing at Different Temperatures

The structure and properties of the Ti–18Zr–15Nb alloy subjected to equal channel angular pressing (ECAP) at 200°С (the number of ECAP cycles n = 1–4) and 500°С (the number of ECAP cycles n = 4 and n = 8) are studied. The main phase of the alloys in all the states is the bcc β phase. No clear presence of X-ray reflections belonging to the secondary α", ω, and α phases is found. The ECAP at 200°С leads to the formation of deformation macrobands that cut the entire sample. As ECAP temperature increases to 500°С, the deformation occurs without the formation of macrobands. According to optical microscopy data, after ECAP, the fragmentation occurs within grains outside of macrobands; microbands and deformation microband packets form. According to transmission electron microscopy data, ECAP results in refining the structure to submicron grains and deformation microbands. The ultimate strength increases as the number of ECAP cycles increases and reaches 960 MPa after ECAP at 200°С with n = 4; however, in this case, the plasticity decreases. The best combination of mechanical properties is achieved after ECAP at 500°С with n = 4; the ultimate strength is 825 MPa at the relatively high plasticity equal to δ = 16%.