材料期刊网

Quaternary Ti-(20-26)Nb-(2-8)Zr-(3.5-11.5)Sn (.wt%) alloys were investigated to evaluate the effects of Zr and Sri on Young's modulus and superelasticity of Ti-Nb-based alloys. X-ray diffraction analysis showed that solution-treated alloys have beta + alpha", beta + omega, alpha" + omega, alpha", or beta microstructures. Zr and Sn increase the lattice parameters of the beta phase; for orthorhombic alpha" matensite, they increase the lattice parameter a but decrease both b and c. The martensitic start temperature of the alpha" is depressed by Zr and Sri additions, whereas the formation of athermal w is dependent on Zr and Sn contents. Differential scanning calorimetry (DSC) measurements show that 1 wt% of Nb, Zr or Sn addition decreases the martensitic start temperature by 17.6, 41.2 or 40.9 K, respectively, due to their negative effect on lattice parameter ratios of the martensite (c/a and b/a). Tensile tests were used to evaluate Young's modulus and superelasticity of the solution-treated alloys. Of the studied alloys Ti-24Nb-4Zr-7.5Sn with single P microstructure has the lowest Young's modulus of 52 GPa and recoverable elastic strain of about 2% at room temperature after cyclic strain. (c) 2006 Elsevier B.V. All rights reserved.