Effect of Mo and Ta on the Mechanical and Superelastic Properties of Ti-Nb Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering.

Damian Kalita,Katarzyna Berent,Anna Góral,Jan Dutkiewicz,Łukasz Rogal

doi:10.3390/ma14102619

Abstract

The effect of ternary alloying elements (Mo and Ta) on the mechanical and superelastic properties of binary Ti-14Nb alloy fabricated by the mechanical alloying and spark plasma sintering was investigated. The materials were prepared in two ways: (i) by substituting Nb in base Ti-14Nb alloy by 2 at.% of the ternary addition, giving the following compositions: Ti-8Nb-2Mo and Ti-12Nb-2Ta and (ii) by adding 2 at.% of the ternary element to the base alloy. The microstructures of the materials consisted of the equiaxed β-grains and fine precipitations of TiC. The substitution of Nb by both Mo and Ta did not significantly affect the mechanical properties of the base Ti-14Nb alloy, however, their addition resulted in a decrease of yield strength and increase of plasticity. This was associated with the occurrence of the {332} <113> twinning that was found during the in-situ observations. The elevated concentration of interstitial elements (oxygen and carbon) lead to the occurrence of stress-induced martensitic transformation and twinning mechanisms at lower concentration of β-stabilizers in comparison to the conventionally fabricated materials. The substitution of Nb by Mo, and Ta caused the slight improvement of the superelastic properties of the base Ti-14Nb alloy, whereas their addition deteriorated the superelasticity.

Highlights

Accepted: 8 May 2021Metastable β-phase titanium alloys, containing only non-toxic alloying elements likeNb, Ta or Zr, are very promising candidates for Ni-free superelastic alloys for application in medicine
This observation is in agreement with the phase composition analysis by X-ray diffractometer (XRD) (Figure 1c)
The effect of the substitution of Nb by Mo and Ta and their addition on the mechanical and superelastic properties was investigated for the binary Ti-14Nb alloy prepared by the mechanical alloying and spark plasma sintering

Summary

Introduction

Accepted: 8 May 2021Metastable β-phase titanium alloys, containing only non-toxic alloying elements likeNb, Ta or Zr, are very promising candidates for Ni-free superelastic alloys for application in medicine. Interesting are alloys from a binary Ti-Nb system due to their excellent biocompatibility, corrosion resistance and mechanical behavior similar to the human bone [1,2]. The superelasticity of those alloys arises from the reverse thermoelastic martensitic transformation that takes place between the body centered cubic (BCC) β parent phase and the orthorhombic α”-martensite [3]. Typical recoverable strains for the solution-treated (ST) alloys are in the range between 1 and 2.5% [5,6,7] These values may be slightly improved by increasing the critical stress for slip deformation

Methods

Results

Conclusion