Abstract
The microstructure and texture of materials significantly influence the mechanical properties and fracture behavior; the effect of microstructure in different zones of friction stir-welded joints of 7A52 aluminum alloy on fracture behavior was investigated in this paper. The microstructural characteristics of sections of the welded joints were tested using the electron backscattered diffraction (EBSD) technique. The results indicate that the fracture is located at the advancing side of the thermomechanically affected zone (AS-TMAZ) and the stir zone (SZ) interface. The AS-TMAZ microstructure is vastly different from the microstructure and texture of other areas. The grain orientation is disordered, and the grain shape is seriously deformed under the action of stirring force. The grain size grows unevenly under the input of friction heat, resulting in a large amount of recrystallization, and there is a significant difference in the Taylor factor between adjacent grains and the AS-TMAZ–SZ interface. On the contrary, there are fine and uniform equiaxed grains in the nugget zone, the microstructure is uniform, and the Taylor factor is small at adjacent grains. Therefore, the uneven transition of microstructure and texture in the AS-TMAZ and the SZ provide conditions for crack initiation, which become the weak point of mechanical properties.
Highlights
The obvious boundary is advancing side of the thermomechanically affected zone (AS-TMAZ), Materials 2021, 14, 6362 and the blurred boundary is RS-TMAZ; this is caused by the different flow rates of plastic metal on both sides of the weld nugget during the welding process
The grain size distribution of different weld zones with Friction stir welding (FSW) welding process is shown in Figure 4, the change range of color is shown in the subscript in the figure, gradually increasing from blue to red
This paper mainly discusses the influence of friction stir welding on the welding process of 7A52 aluminum alloy; it is found that the cracking behavior is caused by different microstructures
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. 7A52 aluminum alloy is a 7 xxx aluminum alloy with low density, high ductility, and excellent corrosion resistance, and has been extensively investigated due to its high strength and hardness [1,2,3] It has been widely employed as a structural material in aeronautics, military competition, and warships [4,5,6]. The effect of microstructure and texture in different zones of 7A52 aluminum alloy FSW joints on mechanical properties are still unclear. This paper mainly presents the following: (1) microstructure and texture analysis of friction stir-welded joint of the 7A52 aluminum alloy; (2) the effect of microstructure on mechanical properties and causes of cracking. The correlation between microstructure and mechanical properties is revealed
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