Influence of the Si content on the microstructure and mechanical properties of Ti–Ni–Cu–Si–Sn nanocomposite alloys

(Ti48Ni32Cu8Si8Sn4)100−xSix (x = 0, 2, 4 and 6) alloys were prepared by levitation melting mixtures of the high purity elements in an Ar atmosphere. Rods of 3 mm in diameter were obtained from the melt by copper mould casting. The effects of Si addition on the microstructure, elastic and mechanical properties of the Ti48Ni32Cu8Si8Sn4 alloy were investigated by scanning electron microscopy, X-ray diffraction, acoustic measurements and nanoindentation. The main phases composing the Ti48Ni32Cu8Si8Sn4 alloy are B2 NiTi, B19′ NiTi and tetragonal Ti2Ni. Additional phases, like Ti5Si3 or Ni2Ti2Si, become clearly visible in samples with higher Si contents. The microstructure evolution is correlated with the obtained mechanical and elastic properties. These alloys exhibit very high hardness values, which increase with the Si content, from 9 GPa (for x = 0) to around 10.5 GPa (for x = 6). The Young's modulus of Ti48Ni32Cu8Si8Sn4 (around 115 GPa) also increases significantly with Si addition, up to 160 GPa for x = 6.

► We study the effects of Si addition of Ti–Ni–Cu–Si–Sn alloy.
► The microstructure evolution is correlated with the obtained mechanical and elastic properties.
► Higher Young's modulus and larger hardness values are obtained in samples with higher Si contents.