Advanced Technology for Preparing Bar from Medical Grade Ti-Zr-Nb Superelastic Alloy Based on Combination of Radial-Shear Rolling and Rotary Forging

Abstract

Prospects are presented for the technology of preparing biomedical Ti–Zr–Nb shape memory alloy 3–8 mm diameter bars more than 2000 mm long using an advanced combination of radial shear rolling and rotary forging. Radial shear rolling parameters are calculated on the basis of technological limitations of true degree and rate of deformation of 0.05–0.5 and 1–5 sec^–1 respectively per pass. Full-scale experimental verification of the technology is performed in NITU MISiS 1030 and 1440 radial shear rolling mini-mills with subsequent rotary forging using an RKM2 machine. Bars are obtained with a grain size of ∼ 40 μm demonstrating superelastic behavior at room temperature with a favorable combination of relatively low Young’s modulus (E = 39 GPa) and relatively high strength (σ_f = 618 MPa). The technology has a high degree of readiness for direct industrial application.