Microstructure and fatigue performance of friction stir welded joints of 2A12‐T4 and 7075‐T6 dissimilar aluminum alloy. Issue 8 (18th August 2020)

• Record Type: Journal Article
• Authors: Zhang, D.F.; Tang, Q.Y.; Wei, T.H.; Lin, Y.H.; Chen, X.W.; Xia, J.
• Is Part Of: Materialwissenschaft und Werkstofftechnik. Volume 51:Issue 8(2020:Aug.)
• Page Start: 1148
• Page End: 1160
• Publication Date: 2020-08-18
• Subjects: Aviation aluminum alloy -- friction stir welding -- dissimilar aluminum alloys -- fatigue -- fracture; Luftfahrt-Aluminiumlegierung -- Rührreibschweißen -- artfremde Aluminiumlegierungen -- Ermüdung -- Bruchverhalten; Materials -- Periodicals; Materials -- Testing -- Periodicals; 620.1
• DOI: 10.1002/mawe.201900113
• Languages: English
• ISSNs: 0933-5137

Abstract

Abstract: The objective of this work is to investigate the microstructure and fatigue performance of friction stir welding joint of 2A12‐T4 and 7075‐T6 dissimilar aluminum alloy. Microstructure shows that the grain growth of heat‐affected zone in both sides of joint is noticeable; the grain size of thermo‐mechanically affected zone in both sides of joint is deformed and distorted in various degrees; nugget zone is fine equiaxed grain with uniform distribution. Microhardness of joint presents an approximate "W" types distribution on the whole, and the highest hardness value of the joint appears near the center of nugget zone, up to 146.5 HV0.2. Since the joint has the higher the fatigue strength ratio, and the S−N curve of the joint shows a smaller downward trend, the joint has the best fatigue performance and 7075‐T6 base metal has the worst fatigue performance. Linear fitting of 7075‐T6 base metal is l n S = - 0 . 172 l n N + 7 . 47812 ; linear fitting of 2A12‐T4 base metal is l n S = - 0 . 189 l n N + 7 . 54361 ; linear fitting of joint is l n S = - 0 . 161 l n N + 7 . 07129 . The fracture analysis presents that the low‐cycle fatigue fracture mechanism of welding joint is quasi‐cleavage fracture, and the main mode of high cycle fatigue fracture is the inter crystalline fracture, mixed with ductile fracture. Abstract : It exists a wide use of aluminum alloys in the field of transportation, especially aerospace vehicles. Among them, dissimilar aluminum alloys welding can meet higher requirements. This paper involved experiments studying the microstructure, quasistatic and cyclic mechanical properties of friction stir welding joint of dissimilar aluminum alloys. Besides, the fitting curves of fatigue test provided the prediction for the connection of aircraft envelop and truss of dissimilar aluminum alloys.