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The mechanical properties and shape memory behavior of Ti–26Nb–(0–1.0)B and Ti–27Nb alloys were investigated. The stress for inducing martensite and the critical stress for slip deformation were greatly affected by increasing B content up to 0.1 at%, and less affected by further increase in B content up to 0.7 at%. The martensitic transformation start temperature decreased suddenly with a slope of 350 K/at% B when B content was less than 0.1 at% and decreased with a smaller slope of 15 K/at% B with further increase in B content up to 1.0 at%. In all samples tested, only superelasticity was observed at room temperature. TEM investigations revealed that the solubility of B in Ti–26Nb alloy was around 0.1 at%. In spite of the low solubility limit, B was effective to stabilize the superelastic behavior by effectively increasing the critical stress for slip deformation. On the other hand, while the stress for inducing martensite increased effectively by the addition of 1.0 at% Nb to the Ti–26Nb alloy, the critical stress for slip deformation remained almost constant and hence superelasticity was deteriorated. [ABSTRACT FROM AUTHOR]

While the stress for inducing the martensitic transformation in a Ti–27Nb alloy changed only slightly on aging, the stress at which the martensite phase starts to plastically deform and the ultimate tensile strength increased on aging due to the formation of thermal ω phase or α phase. An anomalous temperature dependence of the shape memory behavior was also observed and explained by the fact that the thermal ω phase encouraged the formation of the athermal ω phase during cooling. [ABSTRACT FROM AUTHOR]

The biocompatibility of a recently developed Ni-free Ti–16Nb–3Mo–1Sn (at.%) superelastic alloy was investigated both in vitro and in vivo. In addition, static water contact angle (WCA) and electrochemical tests were carried out. Commercial purity Ti (cp-Ti), which is already being used as a clinical material, was used as the control material. The alloy showed a stable corrosion behavior similar to that of the cp-Ti. The WCA measurements showed that the alloy exhibited hydrophilic properties that contributed to cell attachment to implants, as evident by the cytocompatibility tests. According to the in vivo implantation tests conducted on 30 adult BALB/c rats for periods up to 12 weeks, the tissue reaction around the implants was similar for both the cp-Ti and the alloy, and no significant difference was found in almost all parameters analyzed. Due to its stable superelastic properties accompanied with excellent biocompatibility and high corrosion resistance, we believe that this alloy is considered as a promising substitute for the biomedical materials containing Ni or other toxic elements. Unlabelled Image • The Ti–16Nb–3Mo–1Sn superelastic alloy proved an excellent corrosion resistance. • The murine fibroblasts and osteoblastic cells grew well on alloy's surface. • Hydrophilicity of the alloy contributed well to cell attachment to implants. • The alloy showed an excellent in vivo biocompatibility in all rats tested. [ABSTRACT FROM AUTHOR]