Factors influencing the elastic moduli, reversible strains and hysteresis loops in martensitic Ti–Nb alloys

• Ti–xNb (16 wt.% ≤ x ≤ 31 wt.%) alloys were prepared via casting and quenching.
• The influence of Nb content and pre-straining on the elastic behavior was studied.
• As-quenched α″-martensite can exhibit a low Young's modulus of 60 GPa.
• Pre-straining leads to a considerable decrease in Young's modulus by up to 25 GPa.
• Pre-strained alloys are more suitable for use as load-bearing implant materials.

While the current research focus in the search for biocompatible low-modulus alloys is set on β-type Ti-based materials, the potential of fully martensitic Ti-based alloys remains largely unexplored. In this work, the influence of composition and pre-straining on the elastic properties of martensitic binary Ti–Nb alloys was studied. Additionally, the phase formation was compared in the as-cast versus the quenched state. The elastic moduli and hardness of the studied martensitic alloys are at a minimum of 16 wt.% Nb and peak between 23.5 and 28.5 wt.% Nb. The uniaxial deformation behavior of the alloys used is characterized by the absence of distinct yield points. Monotonic and cyclic (hysteretic) loading–unloading experiments were used to study the influence of Nb-content and pre-straining on the elastic moduli. Such experiments were also utilized to assess the recoverable elastic and anelastic deformations as well as hysteretic energy losses. Particular attention has been paid to the separation of non-linear elastic from anelastic strains, which govern the stress and strain limits to which a material can be loaded without deforming it plastically. It is shown that slight pre-straining of martensitic Ti–Nb alloys can lead to considerable reductions in their elastic moduli as well as increases in their total reversible strains.

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