Understanding precipitate evolution during friction stir welding of Al-Zn-Mg-Cu alloy through in-situ measurement coupled with simulation

Abstract

Friction Stir Welding (FSW) imparts both heat and deformation to the metal being joined, producing profound microstructural changes that determine the weld properties. In the case of welding of aerospace aluminium alloys, the most important change is the modification of the size, nature, and fraction of strengthening precipitates. To understand these changes requires the ability to measure the microstructural evolution during the welding process. This paper describes a new tool, the FlexiStir system, a portable friction stir unit designed for use in a high-energy synchrotron beamline that enables in-situ studies of microstructural evolution during FSW. FlexiStir has been used to measure precipitate evolution during FSW of aluminium alloy 7449-TAF and provide time-resolved measurement of precipitate size and volume fraction via small angle X-ray scattering (SAXS). These measurements have been interpreted with the aid of a previously developed microstructural model. The

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

“…In some experimental studies, the post-welding microstructural features, such as recrystallized grain size [13,14], location of marker material [15], and texture characteristic [16], have been analyzed to obtain the inprocess information. Although the experimental approaches, including the in situ observation based on neutron/X-ray [17][18][19], have been developed in recent years, the amount of data were not adequate for understanding the distribution of thermo-mechanical behaviors in three dimensions. In this situation, the numerical simulation has been demonstrated to be a viable tool for the thermo-mechanical analysis for FSW.…”

The Influence of Microstructural Heterogeneity on Mechanical Properties of Friction Stir Welded Joints of T6-Treated Al-Zn-Mg Alloy 7A52

“…In HAZs, the mechanical properties are a strong function of the ratio of η to η phase. Compared to the micro-tensile results, premature failure of the weld joint occurs in HAZs on the advancing side, resulting from stress concentration near the area with the lowest hardness.welding joints [4,[9][10][11][12][13]. These improvements are a result of reduced heat input during FSW compared with conventional fusion weld.…”

“…The solid phase joining of FSW is achieved by introducing frictional heat, interface deformation and solid-state diffusion, which results in gradual local microstructure changes in the aluminum alloy [14,15]. Understanding the microstructural evolution during the thermomechanical process imposed by FSW is a very important step in understanding the weld's mechanical properties.A number of research papers have been published on the development of microstructures and mechanical properties [4,9,11,[15][16][17]. Concerning Al-Zn-Mg alloys, such studies in alloys 7075 [18][19][20][21], 7050 [10,12,22], 7449 [11], 7039 [4,23-27], 7010 [28] are presented.…”

“…welding joints [4,[9][10][11][12][13]. These improvements are a result of reduced heat input during FSW compared with conventional fusion weld.…”

“…A number of research papers have been published on the development of microstructures and mechanical properties [4,9,11,[15][16][17]. Concerning Al-Zn-Mg alloys, such studies in alloys 7075 [18][19][20][21], 7050 [10,12,22], 7449 [11], 7039 [4,23-27], 7010 [28] are presented.…”