Physical metallurgy of Ti–Ni-based shape memory alloys

https://www.tpbin.com/Uploads/Subjects/643149a0-8194-4c67-bf05-73fae6f0d14f.pdf

Development of new metallic alloys for biomedical applications

Alloy design based on single-principal-element systems has approached its limit for performance enhancements. A substantial increase in strength up to gigapascal levels typically causes the premature failure of materials with reduced ductility. Here, we report a strategy to break this trade-off by controllably introducing high-density ductile multicomponent intermetallic nanoparticles (MCINPs) in complex alloy systems. Distinct from the intermetallic-induced embrittlement under conventional wisdom, such MCINP-strengthened alloys exhibit superior strengths of 1.5 gigapascals and ductility as high as 50% in tension at ambient temperature. The plastic instability, a major concern for high-strength materials, can be completely eliminated by generating a distinctive multistage work-hardening behavior, resulting from pronounced dislocation activities and deformation-induced microbands. This MCINP strategy offers a paradigm to develop next-generation materials for structural applications.

Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys

Martensitic transformation, shape memory effect and superelasticity of Ti-Nb binary alloys

Review on titanium and titanium based alloys as biomaterials for orthopaedic applications.

Young's modulus and tensile strength were investigated in relation to phase transformation and microstructural changes occurring during cold rolling and subsequent heat treatment using β (Ti-35 mass%Nb)-4 mass%Sn and (Ti-35 mass%Nb)-7.9 mass%Sn alloys. Stress-induced a" martensite is generated on cold rolling of (Ti-35Nb)-4Sn whose martensitic transformation start temperature is around room temperature. Young's modulus in the rolling direction is lowered by the generation of stress induced a" phase with preferred texture, while it is recovered by the reverse martensitic transformation to ft at 523 K. The reverse transformation yields fine β grains which are elongated approximately along the rolling direction and have an average grain size in width of less than 1 μm. This fine microstructure leads to high strength over 800 MPa with keeping low static Young's modulus of 43 GPa. In contrast, mechanical properties of (Ti-35Nb)-7.9Sn in which matensite is not stress-induced are not so significantly improved by cold rolling and heat treatment.

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Beta TiNbSn Alloys with Low Young's Modulus and High Strength

Composition dependence of Young's modulus inTi-V and Ti-Nb binary alloys and Sn-added ternary alloys quenched fromphase region was investigated at room temperature in relation to the stability ofphase. A minimum of Young's modulus in the binary alloys appears at such a composition that athermal ! phase transformation is almost completely suppressed. Formation of isothermal ! phase by aging after quenching increases Young's modulus. Sn addition to the binary alloys suppresses or retards ! transformation, thereby decreasing Young's modulus. Optimization of alloy composition in Ti-Nb-Sn alloys leads to low Young's modulus of about 40 GPa. The composition dependence of Young's modulus obtained experimentally in this study can be qualitatively explained by the theoretical discrete-variational Xcluster method.

/pdf/beta-ti-alloys-with-low-young-s-modulus-42krsnjx06.pdf

Beta Ti Alloys with Low Young's Modulus

Martensitic transformation and tensile properties of 4 to 5 mol%Sn-doped Ti–16 mol%Nb alloys consisting of biocompatible elements were investigated to provide superelasticity for biomedical applications as a function of heat treatment and Sn content. Martensitic transformation (bcc to orthorhombic structure) is accelerated at such quenching conditions that the bcc parent phase is slightly decomposed. Martensitic transformation temperature decreases rapidly with increasing Sn content. In-situ optical microscopic observation on cooling and heating indicates that the martensite is thermoelastic, corresponding to small temperature hysteresis between the martensitic and the reverse transformations, which is determined by differential scanning calorimetry. By controlling the heat treatment condition and Sn content, large superelastic strain is obtained at room temperature.

/pdf/effect-of-heat-treatment-and-sn-content-on-superelasticity-415r19c8fu.pdf

Sadao Watanabe

Papers

Beta TiNbSn Alloys with Low Young's Modulus and High Strength

Beta Ti Alloys with Low Young's Modulus

Effect of Heat Treatment and Sn Content on Superelasticity in Biocompatible TiNbSn Alloys

Microstructures and mechanical properties of metastable β TiNbSn alloys cold rolled and heat treated

Fabrication of pure Al/Mg-Li alloy clad plate and its mechanical properties