ω Phase Transformation and Mechanical Properties in Binary Zr-Nb Biomedical Alloy

Abstract

The athermal ω phase transformation, magnetic susceptibility and deformation behavior of Zr-xNb alloys (x = 10 and 14) for use in medical devices subjected to magnetic resonance imaging (MRI) were investigated using electrical resistivity measurements, transmission electron microscopy observations and compression tests. The alloy with x = 10 exhibited a positive temperature coefficient in the electrical resistivity curve and the presence of an athermal ω phase at room temperature. On the other hand, the alloy with x = 14 showed an anomalous negative temperature coefficient (NTC) in the resistivity curve. Similar NTCs also appear in β-Ti alloys, which is interpreted as the growth of an athermal ω phase and the appearance of lattice modulation. The ω phase and diffuse satellites, which are possibly related to lattice modulation, were confirmed in the Zr-14Nb alloy at room temperature. The volume fraction of the athermal ω phase and the appearance of lattice modulation are related to the operating deformation mode and Young’s modulus. Thus, controlling the ω phase transformation in Zr-Nb alloys is key to developing medical devices that can be used in MRI.