Microstructure, mechanical properties and fatigue crack growth behavior of friction stir welded joint of 6061-T6 aluminum alloy

Zhang, Lan; Zhong, Huilong; Li, Shengci; Zhao, Hongjin; Chen, Jiqiang; Qi, Liang

doi:10.1016/j.ijfatigue.2020.105556

Cited by 94 publications

(34 citation statements)

References 29 publications

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“…There have been some reports on the fatigue properties of FSW joints of heat treated [15] or numerically analyzed [16] aluminum alloys. However, previous studies focused mainly on the fatigue life [17,18] and crack growth [19][20][21], with only limited studies on the low-cycle fatigue (LCF) behavior of FSW joining in aluminum alloys [22][23][24]. To the authors' knowledge, although the strain-hardened aluminum alloys are readily weldable, FSW resulted in good tensile properties, which must be verified concerning cyclic loading with high strain amplitude.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Low Cycle Fatigue Properties of AA5083 H111 Friction Stir Welded Joint

et al. 2020

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The present paper aims to analyze the microstructure, microhardness, tensile properties, and low cycle fatigue (LCF) behavior of friction stir welded (FSW) butt joints. The material used in this study was the 5 mm thick 5083 H111 aluminum alloy sheet. Butt joints of AA 5083 H111 were manufactured at different operating parameters of the FSW process. The effect of the welding parameters on microstructure, microhardness, and tensile properties was investigated. Based on microstructure analysis and strength tests, the most favorable parameters of the FSW process were settled on the point of view of weld quality. Then, LCF tests of base material and friction stir welded specimens made of 5083 H111 were carried out for the examined welded samples under selected friction stir welding parameters. The process of low-cycle fatigue of 5083 H111 aluminum alloy was characterized by cyclic hardening for both: base material and FSW joint. It was revealed by a decrease in the width of the hysteresis loop with the simultaneous significant increase in the values of the range of stress. It was determined that fatigue cracks are initiated by cyclic slip deformation due to local stress concentration from the surface in the corner of the samples for the base material and the heat-affected zone for FSW joints. For all tested strain amplitudes, the fatigue crack propagation region is characterized by the presence of fatigue striation with secondary cracks.

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Section: Introductionmentioning

confidence: 99%

Microstructure and Low Cycle Fatigue Properties of AA5083 H111 Friction Stir Welded Joint

et al. 2020

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“…Considering that the thickness of CT sample is only 4.5 mm, and the initial values of ΔK is higher than the threshold regime, the effect of residual stress on FCG behavior would not be a major factor in this work, relative to the microstructure. For heat‐treatable alloys, previous works have proved that grain structure and hardening phases are the main microstructure factors on FCG rate 3,31,43 . The EBSD analysis and TEM observation shown in Figures 6 and 7 revealed that the grain structures in BM and AS‐HAZ were approximately similar, while the morphology of hardening phases in these two regions was quite different (Figures 8 and 9).…”

Section: Discussionmentioning

confidence: 84%

Microstructural and fatigue crack growth behavior inhomogeneity of trace Sc added 7085 alloy friction stir welded joint

Jia

Wei

Huang

et al. 2021

Fatigue Fract Eng Mat Struct

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The inhomogeneity of friction stir weld (FSW) joint of a 7085 Al‐based alloy containing trace Sc was investigated by comparing the hardening phase morphology, grain structure, mechanical properties, and fatigue crack growth (FCG) behavior in based metal (BM), heat‐affected zone (HAZ), and weld nugget zone (WNZ). The results showed that microstructural evolution during FSW was remarkably affected by Sc addition. The recrystallization and growth of grains in BM and HAZ were restrained by coherent Al3(Sc,Zr) particles. In HAZ, partially dissolution and slight growth of precipitates resulted in softening but contributed to enhance the FCG resistance according to shear mechanism. In WNZ, high frictional heating and intense plastic deformation induced recrystallization and supersaturated solid solution which decomposed to form new reprecipitates, including many new GPII zones, η′ phases, and some coarse η equilibrium phases attached to grown incoherent Al3(Sc,Zr). Owing to combined influences of fine random orientated grain structure and reprecipitates, WNZ possessed the best fatigue endurance.

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“…A previous study [ 33 ] showed that the fracture mechanism was a mixed fracture mechanism of ductile and quasi-cleavage fracture in the growth region of the inert environment. However, it can be seen from Figure 15 that tearing ridges appeared at the fracture in the growth region of the corrosion fatigue crack, with intergranular fracture [ 17 ] and fatigue speckle characteristics observed between the tearing ridges ( Figure 15 a).…”

Section: Resultsmentioning

confidence: 99%

Corrosion Fatigue Fracture Characteristics of FSW 7075 Aluminum Alloy Joints

Shao

Bai

et al. 2020

Materials

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The corrosion fatigue properties and fracture characteristics of friction stir welding joints of 7075 aluminum alloys were studied via corrosion fatigue tests, electrochemical measurements, and corrosion fatigue morphology and microstructure observations. The results show that the corrosion fatigue crack of the friction stir welding (FSW) joint of 7075 aluminum alloys originated in the junction zone between the thermomechanically affected zone and the weld nugget zone. The corrosion fatigue life of the joint decreased with increasing stress amplitude, with an S–N curve equation of lgN = 5.845 − 0.014S. Multiple crack sources were observed in the corrosion fatigue fracture. The main crack source originated from the corrosion pits at the interface between the thermomechanically affected zone and the weld nugget zone due to the influence of the coarse microstructure and the large potential difference between both zones. Corrosion morphologies of a rock candy block and an ant nest appeared in the crack propagation zone and the grain boundary of the weld nugget zone. In addition, fatigue speckles and intergranular fractures were observed, as well as brittle fracture characterized by cleavage steps and secondary cracks in the final fracture zone.

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Microstructure, mechanical properties and fatigue crack growth behavior of friction stir welded joint of 6061-T6 aluminum alloy

Cited by 94 publications

References 29 publications

Microstructure and Low Cycle Fatigue Properties of AA5083 H111 Friction Stir Welded Joint

Microstructure and Low Cycle Fatigue Properties of AA5083 H111 Friction Stir Welded Joint

Microstructural and fatigue crack growth behavior inhomogeneity of trace Sc added 7085 alloy friction stir welded joint

Corrosion Fatigue Fracture Characteristics of FSW 7075 Aluminum Alloy Joints

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