Phase Formation in Quinary Ti-Based Nanocomposites and an Analogous Ternary System with a View to Thermodynamic Modelling

摘要

The alloy Ti_(60)Cu_(14)Ni_(12)Sn_4Ta_(10) was Cu-mould cast into 3 mm diameter rods and characterised by SEM, TEM and EDX in both microscope types. The results showed that the microstructure of the alloy consists of micron-scale β-Ti dendrites enriched in Sn and Ta surrounded by a binary eutectic consisting of the same β-Ti phase and NiTi with a significant Cu content. The results were compared with those from a ternary Ti-Cu-Ni alloy of analogous composition and it was concluded that the solidification of Ti_(60)Cu_(14)Ni_(12)Sn_4Ta_(10) is based on a metastable equilibrium caused by the kinetic exclusion of the peritectically formed equilibrium phase CuTi_2.