The effect of vanadium and nickel on the microstructure and transformation temperatures of Ti₅₀Pt₅₀ alloy

¹ Advanced Materials Engineering, Manufacturing Cluster, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria, 0001, South Africa
² Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Doornfontein Campus, Johannesburg, 2028, South Africa
³ University of Pretoria, Department of Materials Science and Metallurgical Engineering. Private bag X20, Hatfield 0002, South Africa

^* Corresponding author: TMotsai@csir.co.za
^* EMakhatha@uj.ac.za

Abstract

Significant research has been done to produce shape memory alloys that have good shape memory properties and high martensitic transformation temperatures. The Ti₅₀Pt₅₀ alloys have been found to have high transformation temperature of around 1050℃ however, they exhibit negligible shape memory properties. The solid solution strengthening, and improved shape memory properties could be enhanced by ternary alloying. Therefore, this work investigates the effect of varying V and Ni contents, in the range of 6.25 to 12.5at%, on the austenitic and martensitic transformation temperatures, and hardness of the equi-atomic Ti₅₀Pt₅₀ alloy. Arc melting followed by casting and solution heat treatment was carried out to produce the alloys. As-produced alloys were characterized by using scanning electron microscopy, differential scanning calorimetry and hardness testing. The microstructures showed high volume fraction of second phases formed in the TiPtV alloy compared with Ti₅₀Pt₅₀ and TiPtNi alloys. The multiple phases formed in the TiPtV alloys could be the cause of high hardness values observed in these alloys as compared withTi₅₀Pt₅₀ and TiPtNi alloys. Thermal transformation studies revealed that TiPtV alloys exhibit transformation temperature close to Ti₅₀Pt₅₀ alloy, in contrast with TiPtNi alloys. TiPtNi alloys thermal behaviour was improved by solution heat treatment.