The Machining Characteristics of a TiNiAl Ternary Shape Memory Alloy Using Electro-Discharge Machining

• Main Authors: Jian-Jihi Wu, 吳建緻
• Other Authors: Ming-Horng Lin
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/23516397055480594675

碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 99 === This study investigates the influence of the machining characteristics on TiNi-based 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 tP, can significantly affect the EDM characteristics. Experimental results reveal that the material removal rates (MRRs) of TiNi-based SMAs in the EDM process exhibit a reverse relationship to the product of the alloy’s melting temperature ( l ) and thermal conductivity (J), i.e., the MRRs will have the sequence Ti50Ni50 >Ti49.4Ni50.2Al0.4 > Ti35.5Ni49.5Zr15. Having a least l*J value, Ti50Ni50 alloy has the largest Ra value and craters diameter, Ti49.4Ni50.2Al0.4 alloy the next largest and Ti35.5Ni49.5Zr15 alloys the smallest after electro-discharge machining. The recast layer consists of the oxides Ti2O3, ZrO2, NiO, TiO and the deposition particles of the consumed Ti electrode and dissolved de-ionized water. The TiO oxides in the recast layer can be identified by XPS and TEM. The hardening effect near the outer surface for EDMed Ti49.4Ni50.2Al0.4 alloy originates from the recast layer. The thickness of the recast layer and the value of contact angle vary with the electro-discharge energy.