纳米复合材料(Cu/AlN)点焊电极的失效机制分析

Analysis on Failure Mechanism of Nano-composite (Cu/AlN) Electrodes for Spot Welding

通过高能球磨制备铜基纳米氮化铝复合粉体(Cu/AlN),用粉末冶金方法制备Cu/AlN点焊电极并装机进行镀锌薄钢板点焊试验。用XRD、SEM、TEM等表征失效电极的组织形貌,分析电极的失效机制及失效原因。结果表明:铜基纳米复合材料(Cu/AlN)点焊电极的主要失效机制是:"蘑菇化"变形、坑蚀、粘结等,未见电极表面合金化生成新相。Cu/AlN点焊电极使用性能优于铸态商用(CuCrZr)点焊电极,主要因为纳米AlN颗粒的弥散强化作用及其优异的导热性能。

Performances of nano-composite（Cu/AlN）electrodes for spot welding were rationalized when it failed after welding 0.8mm thickness galvanized steel sheets with a welding current of 7.5kA,welding pressure of 0.4MPa,welding 8 cycles.The electrode was made by powder metallurgy（PM）using nano-AlN and copper composite powders through high-energy ball-milling.The morphologies and micro-structures of the electrodes after failure were characterized using X-ray diffractometry（XRD）、scanning eletron microscopy（SEM）、transmission electron microscopy（TEM）etc.Its failure reasons were analyzed.The results show that the failure of nano-composite（Cu/AlN）electrodes is primarily mushroom-shape deformation、pits and adherence corrosion,and there is no alloying effect or new phases on the surface of the electrode.Nano-composite（Cu/AlN）electrodes for spot welding perform better than forged commercial（CuCrZr）electrodes because of the dispersion reinforcement of nano-AlN particles and its super thermal conductivity.