Effects of Ta addition on the microstructure and transformation temperatures of Ni۴۸.۵Ti۴۶.۵Hf alloy

Ta was added to Ni۴۸.۵Ti۴۶.۵Hf۳ alloy to increase the transformation temperatures of the alloy.This study investigated the effects of addition of ۲ and ۳ percent Ta on the microstructure andtransformation temperatures. Microstructural observations were performed using optical andscanning electron microscopy equipped (SEM). The dilatometry technique was performed onthe studied alloys to evaluate the effect of Ta content on transformation temperatures. SEMmicrographs indicated the microstructure of the Ni۴۸.۵Ti۴۶.۵Hf۳Ta۲ and Ni۴۸.۵Ti۴۵.۵Hf۳Ta۳ alloyscontaining B۲ phase and (Ti,Hf)۲Ni precipitates. Furthermore, SEM results showed that withaddition of ۳% Ta to the Ni۴۸.۵Ti۴۶.۵Hf۳ alloy, a new white phase Ta-rich appeared in themicrostructure of alloy. Both transformation temperatures increased significantly in theNi۴۸.۵Ti۴۶.۵Hf۳Ta۲ alloy.