Cr-Zr-Cu alloy electrodes for resistance spot welding of aluminiam alloy are treated by deep cryogenic treatment processes.The Cr-Zr-Cu alloy electrodes are analyzed by transmission electron microscope(TEM),and results show that the common dislocation in Cr-Zr-Cu alloy electrodes is changed into the dislocation loop,and twin crystal is found after deep cryogenic treatment.The parallel twin crystal band is observed by selected electron diffraction(SED)and the twin crystal plane is marked as(111).The Cr-Zr-Cu alloy electrode is studied by X-ray diffraction(XRD)and results show that the intensity of diffraction peak is obviously changed after deep cryogenic treatment,and the grain rotates to preferred orientation.The Cr-Zr Cu alloy electrode is studied by positron annihilation technique(PAT)and results indicate that the amount of vacancy defects is less than that of Cr-Zr-Cu alloy before deep crybgenic treatment.The main elements in Cr-Zr-Cu alloy are studied with X ray photoelctron spectroscopy(XPS)and the intensity of spectrum peak is increased after deep cryogenic treatment.