Tensile Properties of Quenched Binary Ti-Mo Alloys for Potential Use as Orthopedic Implants

This study investigated the tensile properties of quenched Ti-xMo alloys for potential use in load bearing implants. Two binary alloys: Ti-17Mo and Ti-20Mo (designated: TM17 & TM20) were designed using theoretical predictive methods such as the molybdenum equivalence (Mo_eq) and the electron to atom (e/a) ratio. The alloys were fabricated using the ultrasonic atomization machine with a plasma melting system. Produced ingots were then heat treated at 1100 ℃ in a muffle furnace and quenched in ice-brine. Phase and microstructural analyses were conducted using the X-ray diffraction (XRD), and the optical microscope (OM). The mechanical properties were analysed using the tensile and micro-hardness tests. The Mo_eq, increased from 17 to 20wt%, the e/a ratio increased from 4.186 in TM17 to 4.222 in TM20 theoretically indicative that the β is stable in these compositions without the presence of other phases. This was further substantiated by the XRD results which showed peaks of bcc β in TM17 and TM20 alloy. The OM micrographs in TM17 illustrated equiaxed β grains with substructures inside the grains which was not in agreement with the predictive methods and TM20 were comprised equiaxed β grains only. Elastic modulus increased slightly with an increase with Mo content from 82 GPa in TM17 to 84 GPa in TM20. Ultimate tensile strength showed similar trend with the elastic modulus where the strength increased from 912 MPa to 920 MPa, respectively. The fracture surfaces depicted a combination of ductile and brittle fracture in both alloys.