Fatigue crack propagation near the interface between Al and steel in dissimilar Al/steel friction stir welds

The Friction Stir Welding (FSW) is a dynamically developing version of the pressure welding processes. High-quality welded joints can be created using this process for different engineering applications (e. g. automotive parts). Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed to demonstrate the behaviour of the friction stir welded joints under cyclic loading conditions. Fatigue Crack Propagation (FCG) experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints. The CT type specimens were cut parallel and perpendicular to the characteristic directions of the base materials and the welded joints, and the notch locations in the specimens of welded joints were different, too. Therefore, the propagating cracks represent the possible directions of the fatigue cracks both on the base materials and on the welded joints. The results of the fatigue crack propagation tests on the welded joints clearly demonstrate the different characteristics of the thermo-mechanically affected zone (TMAZ), the heat affected zone (HAZ), and the advancing (AS) and retreating sides (RS) of the weld nugget (WN). The investigations and their results were compared with each other and with the results can be found in the literature.

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Fatigue crack propagation behavior of friction stir welded 5083-H32 Al alloy

Journal of Materials Science ◽

10.1007/s10853-007-1630-x ◽

2007 ◽

Vol 42 (23) ◽

pp. 9888-9893 ◽

Cited By ~ 10

Author(s):

Seongjin Hong ◽

Sangshik Kim ◽

Chang Gil Lee ◽

Sung-Joon Kim

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Al Alloy ◽

Friction Stir ◽

Fatigue Crack Propagation Behavior ◽

Propagation Behavior ◽

Crack Propagation Behavior

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A Study on Fatigue Crack Propagation for Friction Stir Welded Plate of 7N01 Al-Zn-Mg Alloy by EBSD

Materials ◽

10.3390/ma13020330 ◽

2020 ◽

Vol 13 (2) ◽

pp. 330 ◽

Cited By ~ 4

Author(s):

Wenyu Liu ◽

Dongting Wu ◽

Shuwei Duan ◽

Tao Wang ◽

Yong Zou

Keyword(s):

Fatigue Crack ◽

Plastic Zone ◽

Crack Propagation ◽

Base Metal ◽

Fatigue Crack Propagation ◽

Lattice Distortion ◽

Stir Zone ◽

Rolled Plate ◽

Alloy Plate ◽

Friction Stir

EBSD (electron backscattered diffraction) was used to study the fatigue crack propagation mechanism in a friction stir welding joint of a 15 mm-thick 7N01 aluminum alloy plate. Crack tips with detailed features were clearly characterized by EBSD images. The plastic zone caused by crack was small in the stir zone. Due to the fine grain strengthening in the stir zone, there were several lattice distortion regions which were observed in the BC (band contrast) map but disappeared in the SEI (secondary electron image). In the stir zone, fatigue crack tends to awake and grow along grain boundaries, and propagate with little deformation of the grains. When the crack tries to grow across a boundary, the deformation of the plastic zone at the crack tip shows little correlation to the cyclic loading direction. However, the plastic zone in base metal, the rolled plate, is large and continuous, and no obvious lattice distortion region was found. According to Schmidt factor, the base metal near crack is fully deformed, lots of low angle boundaries parallel to the cyclic force can be observed. The base metal showed a better ability for fatigue crack propagation resistance.

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Simulations of fatigue crack propagation in friction stir welds under flight loading conditions*

Materials Testing ◽

10.3139/120.100746 ◽

2006 ◽

Vol 48 (7-8) ◽

pp. 370-375 ◽

Cited By ~ 4

Author(s):

Tommaso Ghidini ◽

Claudia Polese ◽

Agostino Lanciotti ◽

Claudio Dalle Donne

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Loading Conditions ◽

Friction Stir

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Fatigue Crack Growth Rates in Friction Stir Welding Joints of 7075-T6 Al Alloy and Fatigue Life Prediction Based on AFGROW

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.337.507 ◽

2011 ◽

Vol 337 ◽

pp. 507-510 ◽

Cited By ~ 2

Author(s):

Bin Lian Zou ◽

Xin Qi Yang ◽

Jia Hua Chen

Keyword(s):

Fatigue Crack ◽

Friction Stir Welding ◽

Fatigue Crack Growth ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Crack Propagation ◽

Al Alloy ◽

International Institute ◽

Welding Seam ◽

Friction Stir

In this work, a study of fatigue crack propagation (FCP) behavior of friction stir welding (FSW) joints of 7075-T6 aluminum alloy was carried out. Fatigue crack growth rate curves were determined for cracks growing in different locations of the welding lines, including prefabricated crack through welding seam center, advancing side (AS), retreating side (RS), and vertical to welding seam. A computational simulation of fatigue crack propagation was conducted by AFGROW with different stress ratios R, and the effects of R on FCP rate were analyzed. Results showed that the FCP rate in RS of the Heat Affected Zone (HAZ) was the lowest and the highest was in the region vertical to the welding seam. In the low stress intensity factor range (△K) region, the FCP rate in Nugget Zone (NZ) was lower than that in AS of the HAZ, but in the high △K region, the situation was contrary. Reasons of the results were analyzed. Compared with the standard of International Institute of Welding (IIW), FCP rates in all regions were lower and it concluded nice fatigue properties of FSW 7075-T6. The simulation made in terms of crack propagation rate (da/dN) versus △K generally showed a good agreement with the measured values. The study of effects of different R on FCP rates based on AFGROW indicated that FCP rates increased with increasing R.

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