Measurement of phase equilibria in Ti-Ni-Sn system
(School of Materials Science and Engineering, Central South University, Changsha 410083, China)
Abstract: Phase relations of the Ti-Ni-Sn ternary system were investigated via alloy sampling assisted with X-ray diffractometry (XRD) and electron probe micro-analysis (EPMA). A new binary phase with composition of TiSn4 (molar fraction, %) was detected at 508 K. In addition, a supplementary phase (Ti1-x-yNixSny)Ni3 (τ, AuCu3-type) was observed at 873 and 973 K. According to the characterised microscopic structure in various annealed alloys, four ternary phases were detected in Ti-Ni-Sn ternary system: TiNiSn, TiNi2Sn, Ti2Ni2Sn and (Ti1-x-yNixSny)Ni3. Additionally, isothermal sections of Ti-Ni-Sn ternary system at 508, 873 and 973 K were constructed. By comparing three isothermal sections, a peri-eutectic reaction, L+TiNi2Sn→Ni3Sn4+TiNiSn, was deduced, which occurs at a temperature between 873 and 973 K. Furthermore, the solubility of Sn in TiNi and Ni in Ti5Sn3 was detected.
Key words: isothermal section; Ti-Ni-Sn system; phase equilibria