| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 99 === This study investigates the influence of the machining characteristics on Ti35.5Ni48.5Zr16 and Ni60Al24.5Fe15.5 high temperature shape memory alloys (SMAs) using multiple-electrodes in die-sinking EDM. The material’s intrinsic properties and several machining parameters, e.g. the electrode material, electrode polarity, discharge current IP and pulse duration P, can significantly affect the EDM characteristics, which can be included the material removal rates (MRRs), electrode wear rate, surface topography, recast layer thickness and compositional analysis. Experimental results reveal that the material removal rates of high temperature SMAs in the EDM process exhibit a reverse relationship to the product of the alloy’s melting temperatureand thermal conductivity, i.e., the MRRs of Ni60Al24.5Fe15.5 alloy have the larger than that of Ti35.5Ni48.5Zr16. Having a least value, Ni60Al24.5Fe15.5 alloy has the largest Ra value and craters diameter than that of Ti35.5Ni48.5Zr16 alloy after electro-discharge machining. The recast layer consists of the oxides TiO, ZrO2, NiO, Al2O3 and the deposition particles of the consumed Ti electrode and dissolved de-ionized water. The oxides TiO, ZrO2, NiO, Al2O3 in the recast layer can be identified by XPS. The specimen’s hardness near the outer surface can reach 700 Hv for EDMed Ti35.5Ni48.5Zr16 alloy. The thickness of the recast layer and the value of contact angle vary with the electro-discharge energy. The EDMed Ti35.5Ni48.5Zr16 alloy shows the hydrophobicity due to having the lower surface energy of the oxide layer.
Keywords:EDM, shape memory alloys, recast layer thickness, XPS, hydrophobicity
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