Effect of deep cryogenic treatment on microstructure and mechanical properties of friction-stir-welded joints of 5A06 aluminum alloy

In order to avoid softening and improve the mechanical properties of the aluminum alloy welded joints,the butt test of 5A06 aluminum alloy was carried out with FSW,and the welded joints were processed into metallographic samples and tensile samples of a certain size under the conditions of a rotating speed of 1 200 r/min and a welding speed of 150 mm/min,the effect of deep cryogenic treatment (DCT) time on microstructure and mechanical properties of friction-stir-welded joints of 5A06 aluminum alloy was investigated.The experiments were carried out by microstructure observation test,micro-hardness test and tensile test to characterize and analyze the joint organization and mechanical properties.The experiment results show that DCT can refine the grain and promote the precipitation of the second phase,thus the mechanical properties of the joints are improved.The tensile strength and elongation of the joints can reach 385.3 MPa and 17.2% respectively,which are increased by 7.4% and 23.7%,respectively after 12 h DCT compared with the joints without DCT.Therefore,DCT can effectively improve the mechanical properties of aluminum alloy joints and provide theoretical and technical basis for its application.