|
At present, FSW has been widely used at aerospace, ship-building, railways, automobiles and other fields. at home and abroad, people evaluate the joint of FSW of aluminum alloy by microstructure, mechanical properties and fatigue properties, but largely overlook an important feature of aluminum–ageing strengthening. Therefore, the study of the effluence of the aging process on FSW joint is with important significance.The objective of this paper is to find the impact of aging on the joints of FSW of 2024-T3 aluminum alloy under the three systems–the natural aging, 180℃/10h, 45℃/12h, in order to provide reference for the aging system when ascertain ageing condition of aluminum FSW joints .By using microstructure, hardness, stretching, bending, and other means people test the joint. The results show that the microstructure of the natural aging joints at the corresponding regions in various period has no significant change; Comparison of three aging joints, its microstructure has also failed to find a clear distinction, but after XRD diffraction, finds that the Weld Nugget of 45℃/12h has more S precipitation than the other two, which leads to its hardness higher than the other two. From the distribution of the hardness of the cross area of the joint, natural aging and 45℃/12h have the same trend, but the latter is high than the former; 180℃/ 10h has no regular distribution, but the hardness of the Thermal Mechanical Affected Zone is higher than the Nugget. From the local area, weld joints hardness fluctuates in the first and second cycle of the natural aging, and from the third cycle, the hardness of stabilizes. After 45℃/12h the fluctuations in the hardness is the largest, and 180℃/10h is the second, then the fifth period of natural ageing is the lowest. Because there are shortcomings, which lead to the decline of tensile strength, elongation of the joint aged by three ageing system respectively. However, excluding impact of defects, the aging joints is better than welded, and the natural aging is better than artificial aging.
|