Friction-stir welding of an Al–Mg–Sc–Zr alloy in as-fabricated and work-hardened conditions

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tThe effect of prior work hardening on the microstructure and mechanical properties of a friction-stir welded (FSWed) Al-5.4Mg-0.2Sc-0.1Zr alloy was investigated. The microstructure of the final stir zone was shown to be weakly dependent on the initial condition of the base material; FSW led to the formation of fully recrystallized microstructures with average grain sizes ranging from 1.2 to 1.5 μm and a moderate dislocation density of $ 3.57 1.5 Â 10 13 m À 2 in the stir zone. The nano-scale Al 3 (Sc,Zr) dispersoids coarsened from 9 to $ 15 nm but retained a coherent relationship with the matrix. In contrast, the joint efficiency of the obtained welds was very sensitive to the initial material condition. Nearly full strength joints were obtained in both annealed (O) and partially hardened and stabilized (H323) conditions. However, the joint efficiency was only 65% in the fully hardened condition (H18). The relatively low weld strength for the alloy in the H18 condition was attributed to the elimination of dislocation and substructure strengthening during FSW.

Cold-Rolling Strain Hardening Effect on the Microstructure, Serration-Flow Behaviour and Dislocation Density of Friction Stir Welded AA5083

“…In addition, the changes of wrinkle behaviour in the PWCRed-40% sample are consistent with the ideas of a homogeneously uniform distribution of the dislocations. The uniform plastic flow is suggested to occur in those subjected to a regular form and finer grain of Al [49][50][51]. Cold working leads to two remarkable changes in the microstructure of materials, namely, grain size and dislocation density, which in turn affect the performance enhancement of the materials.…”

Superplasticity of friction-stir welded Al–Mg–Sc sheets with ultrafine-grained microstructure

“…Therefore, the conventional technologies are obviously not appropriate for this processing route. In contrast, the friction-stir welding (FSW) technique enables preservation of the fine-grained structure [10][11][12][13][14] and avoids dissolution of the unique Al 3 Sc dispersoids [7][8][9][14][15][16][17][18][19][20] in the weld zone, making FSW particularly promising for use in the joining of UFG Al-Mg-Sc alloys.…”

“…Therefore, the conventional technologies are obviously not appropriate for this processing route. In contrast, the friction-stir welding (FSW) technique enables preservation of the fine-grained structure [10][11][12][13][14] and avoids dissolution of the unique Al 3 Sc dispersoids [7][8][9][14][15][16][17][18][19][20] in the weld zone, making FSW particularly promising for use in the joining of UFG Al-Mg-Sc alloys.Recent studies have demonstrated that friction-stir processed Al-Mg-Sc alloys exhibit excellent superplastic properties [21][22][23][24][25][26][27][28]. Specifically, the maximum elongation-to-failure value may sometimes exceed 2000% [21, 24, 27].…”

Investigation into the Dissimilar Friction Stir Welding of AA5052 and AA6061 Aluminum Alloys Using Pin-Eccentric Stir Tool

“…It has been reported that the cooling rate elevates with increasing pin eccentricity [33]; however, the application of pin eccentricity hardly affected the evolution of strengthening precipitates in the present work. Based on our previous studies [34], coarsening proceeds rapidly if there is an existing population of precipitates available for growth: the amount of initial GP zones in the matrix is high, and thus, the coarsening proceeds completely in a relatively short period, weakening the impact of the cooling rate, and therefore, the distribution and morphology of strengthening precipitates in all joints are similar. Figure 10 shows the hardness results of FSW joints produced by different pin-eccentric stir tools, and the hardness distribution profile was asymmetric due to the different mechanical properties between AA5052 and AA6061.…”

“…The inhomogeneous microstructure led to the mixed fracture and reduced the plasticity of the joints. By contrast, the fracture surfaces of joints P0.4 and P0.8 were characterized by fine and round equiaxed dimples, which indicated that the application of pin eccentricity homogenized the microstructures in the NZ and the mode of failure changes into ductile fractures [34], increasing the plasticity of pineccentric FSW joints. The average hardness of the NZ elevated as the pin eccentricity increased, which elevated from 61 HV for joint P0 to 66 HV for joint P0.8 (Figure 10b).…”