Microstructure, mechanical and shape memory properties of Ti–55Pd–5x (x=Zr, Hf, V, Nb) alloys

Microstructure, mechanical and shape memory properties of homogenized Ti–55Pd–5x (x=Zr/Hf/V/Nb) (at%) ternary alloys were investigated to identify potential alloy systems for functional applications in the temperature range of 400–600 °C. The four characteristic temperatures of these alloys were observed to be in the desired temperature range. The yield strengths of martensite and austenite phases were measured to be better than reported for binary Ti–Pd alloys. Two kinds of microstructure developed in these alloys: (i) Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys had B19 martensite as their matrix phase with a significant amount of (Ti, x)2Pd3 and Pd3(Ti, x) (x=Zr or Hf) precipitates; (ii) Ti–55Pd–5V and Ti–55Pd–5Nb alloys had (Ti, x)2Pd3 (x=V or Nb) phase as their major phase along with a small amount of martensite phase. As a result, Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys exhibited significant shape memory; the maximum observed shape memory strain was 1.69% for Ti–55Pd–5Hf alloy. The non-transformable nature of (Ti, x)2Pd3 phase was responsible for the poor shape memory behavior of the other two alloys.