Surface Modification of TiNi-based Shape Memory Alloys by Gas Electrical Discharge Machining

• Main Authors: Wei-Tse Chang, 張為澤
• Other Authors: Shy-Feng Hsieh
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/14214919241453386839

碩士 === 國立高雄應用科技大學 === 模具工程系碩士班 === 101 === This study investigates the properties of the recast layer of Ti50Ni50, Ti50Ni49.5Cr0.5 and Ti40.5Ni49.5Zr10 ternary SMAs using electrical discharge machining (EDM) in gas. The mixture of gases N2 or N2 + C2H2 is used as a dielectric medium, the electrode used were made of titanium (99.7wt%) hollow thin-tube . After EDM process, the surface morphology, cross-sectioned microstructures of the recast layer, phase transformation, adhesion strength between matrix and recast layer are also studied. Many electro-discharge craters and recast materials are observed on the EDM surface of these SMAs. Surface roughness value Ra and MRR increase with increasing the pulse energy and has a reverse relationship to the thermal conductivity of these SMAs. The recast layer consists of TiN, CrN and ZrN nitrides for EDM in N2 gas, but TiC and TiCN for the mixture of N2 + C2H2 gases. A higher adhesion strength can be found with the thinner thickness of these layer in these SMAs. The higher specimens’ hardness near the outer surface in EDM process can be obtained. The TiNi-based SMAS still exhibit a good shape recovery after EDM in gas.