Electrical discharge machining of a NiAlFe ternary shape memory alloy

The electro-discharge machining (EDM) characteristics of a NiAlFe ternary shape memory alloy (SMA) have been investigated in this study. Experimental results reveal that the material removal rates (MRRs) of Ni60Al24.5Fe15.5 and Ti35.5Ni49.5Zr15 alloys in the EDM process exhibit a reverse relationship to the product of the alloy's melting temperature and thermal conductivity. In addition, a precise EDM machining of NiAlFe SMA can be obtained by setting the machine parameters at low pulse energy. The surface roughness (Ra) of the EDMed NiAlFe SMA is found to follow the empirical equation of Ra = λ(IP × τP)β. Having a less TΘ × KT value, Ni60Al24.5Fe15.5 alloy has a larger Ra value than that of Ti35.5Ni49.5Zr15 alloy after electro-discharge machining. The recast layer consists of the oxides Fe2O3, Al2O3, NiO and the deposition particles of the consumed Cu electrode and dissolved dielectric medium. The hardening effect near the outer surface for EDMed NiAlFe alloy originates from the recast layer. The thickness of the recast layer varies with the pulse duration and exhibits a minimum value at the maximal MRR.