Stiffness and hardness gradients obtained by laser surface melting of an aged β-Ti alloy

Abstract

Components with variable stiffness have been attracting interest because of their potential for use in biomedical implants. Here, a β-titanium alloy aged under different conditions was subjected to laser surface melting (LSM). The high cooling rate typical of LSM avoided α-phase precipitation in the fusion zone (FZ) and heat-affected zone (HAZ) as the α precipitates were solid-solutioned into the β phase, producing a surface layer with full β phase over the aged substrate and reduced stiffness and hardness. The decrease in stiffness occurred independently of the aging condition used while the decrease in hardness was greater for the sample aged at the lower temperature as this had finer precipitates. A route involving aging at this lower temperature and LSM is proposed for use when a graded material combining a less rigid surface with the original core stiffness and strength is required, as in orthopedic implants.