Hot working behaviour of low-cost Ti-3.4Fe bio-implant alloy

Abstract

This study investigated the hot workability of an experimental, non-toxic, low-cost Ti-3.4Fe alloy using flow stress analysis, constitutive modelling, processing maps and microstructural examination. Hot compression tests were performed on Ti-3.4Fe alloy samples at different deformation temperatures (750, 800, 850 and 900 °C), strain rates (0.05, 0.1, 1 and 10 s−1) and a total strain of 0.6. The compression tests were performed using a Gleeble® 3500 thermomechanical simulator. The isothermally compressed samples were analysed using a scanning electron microscope to assess the microstructure. An Arrhenius-based model was used to derive the constitutive constants. From the results, the stress exponent and activation energy were 4.91 and 611 kJ.mol−1 under the steady-state stress condition and 5.32 and 675 kJ.mol−1 at peak stress. The stress exponents suggested a dislocation climb and glide mechanism controlling deformation. The processing map showed that the optimum conditions to deform Ti-3.4Fe were 850 °C at a strain rate of 0.1 s−1 for both steady-state and peak stresses. The microstructure revealed kinked, rotated and bent lamella at the safe region (850 °C at 0.05 s−1), confirming the dominance of dynamic recovery as the softening mechanism. Instabilities manifested as cracks and inhomogeneity at 750 °C and 1 s−1 and at 850 °C and 10 s−1.