Effect of Hafnium Alloying on the Structure, Phase Composition and Properties of Cold-Deformed Biocompatible Zr51–xTi31Nb18Hfx (x = 2 – 10 At.%) Alloys Subjected to Annealing

Abstract

Cold-deformed biocompatible alloys Zr_51–xTi₃₁Nb₁₈Hf_x (x =2– 10 at.%) are investigated after 1-h annealing at 700°C and furnace cooling. The structure, phase composition and texture of the alloys are studied using x-rays phase analysis, scanning electron microscopy and electron backscatter diffraction after micro-indentation and tensile testing. A methodology tested on titanium alloys is used to derive a formula for calculating the temperature of transition of zirconium alloys to a single-phase β-range (the temperature of polymorphic transformation T_pt). It is shown that decrease in the hafnium content provides more developed recrystallization and decelerates the decomposition of the β-solid solution during annealing yielding different second phases (ω, α″, α). The effect of the alloying with hafnium on the textural condition of the alloys during annealing is considered. The relation between the structural and phase conditions of the alloys and their physical and mechanical properties is established and recommendations are developed on the hafnium content ensuring a balanced combination of properties.