Vacuum Induction Melting of Ternary NiTiX (X=Cu, Fe, Hf, Zr) Shape Memory Alloys Using Graphite Crucibles

Abstract

In the present study we investigate vacuum induction melting (VIM) of prominent ternary NiTiX (X ¼ Cu, Fe, Hf, Zr) shape memory alloys using graphite crucibles. We apply a melting procedure which was recently developed for binary NiTi alloys and which keeps the carbon pick-up during melting at a minimum. We investigate the microstructures of the as-cast and homogenized alloys using scanning electron microscopy (SEM) in combination with energy dispersive X-ray analysis (EDX). Differential scanning calorimetry (DSC) was performed to study the phase transformation temperatures of the as-cast and homogenized materials. The results show that VIM processing in graphite crucibles provides ternary NiTiX shape memory alloys with good chemical homogeneity and acceptable impurity contents.