In this study, mechanical and microstructural characteristics of AA5XXX aluminum plates connected by MIG welding were investigated. Thus, after several preliminary experiments done to ensure quality requirements of the parameters, specimens in the form of long aluminum plates were welded, and then some of them were spared for the subsequent sub-zero treatment at about 146 degrees C for 12 and 24 h, respectively. To investigate the effect of this super cooling on the welded parts, several tensile, bending, and hardness tests in conjunction with micro-structure examinations were carried out and results were discussed in detail. It was concluded that during sub-zero treatment, microstructure gets finer and stabilized, positively affecting the overall strength of the material. There is no significant difference in the overall strength of the material right after the subzero treatment and that of the specimens rested for one year at room temperature after cryogenics treatments. (C) 2017 Sharif University of Technology. All rights reserved.