Effect of Stirring Pin Rotation Speed on Microstructure and Mechanical Properties of 2A14-T4 Alloy T-Joints Produced by Stationary Shoulder Friction Stir Welding.

Haifeng Yang,Xinxin Xu,Huijie Liu,Huihui Zhao,Li Zhou,Hongyun Zhao

doi:10.3390/ma14081938

Haifeng Yang, Xinxin Xu + Show 4 more

Open Access

https://doi.org/10.3390/ma14081938

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Journal: Materials	Publication Date: Apr 13, 2021
Citations: 7	License type: CC BY 4.0

Affiliation: Harbin Institute of Technology

Abstract

In this study, 2A14-T4 Al-alloy T-joints were prepared via stationary shoulder friction stir welding (SSFSW) technology where the stirring pin’s rotation speed was set as different values. In combination with the numerical simulation results, the macro-forming, microstructure, and mechanical properties of the joints under different welding conditions were analyzed. The results show that the thermal cycle curves in the SSFSW process are featured by a steep climb and slow decreasing variation trends. As the stirring pin’s rotation speed increased, the grooves on the weld surface became more obvious. The base and rib plates exhibit W- or N-shaped hardness distribution patterns. The hardness of the weld nugget zone (WNZ) was high but was lower than that of the base material. The second weld’s annealing effect contributed to the precipitation and coarsening of the precipitated phase in the first weld nugget zone (WNZ1). The hardness of the heat affect zone (HAZ) in the vicinity of the thermo-mechanically affected zone (TMAZ) dropped to the minimum. As the stirring pin’s rotation speed increased, the tensile strengths of the base and rib plates first increased and then dropped. The base and rib plates exhibited ductile and brittle/ductile fracture patterns, respectively.

Highlights

Aluminum alloy T-joints, as integral parts of load-bearing structures, can bear both unidirectional and combined stresses, thereby effectively improving the rib plates’ stability without affecting the component’s overall quality
T-joints can generally be prepared via Friction stir welding (FSW) by passing through the rib plate to the base plate [11,12]
stationary shoulder friction stir welding (SSFSW) has a unique advantage in the welding of T-joint welded joints, i.e., the welding can start from the inside of the joint only by processing the shaft shoulder into a special rectangular shape

Summary

Introduction

Aluminum alloy T-joints, as integral parts of load-bearing structures, can bear both unidirectional and combined stresses, thereby effectively improving the rib plates’ stability without affecting the component’s overall quality. Friction stir welding (FSW) is a novel solid-state bonding technique developed by The Welding Institute (TWI, Cambridge, UK) [7,8] It possesses many advantages, such as low thermal input, slight residual deformation, high material utilization, and favorable automation degree during the butt welding of aluminum alloy plates [9,10]. Gascoyne et al [20] analyzed the microstructures of the SSFSW T-joints They found that, the appearance of blades is connected with the design structure of the tool and the thread of the stirring pin, which certainly depends on the welding parameters and the properties of the base materials. It examined the forming quality on the weld surface, the evolution of microstructures, and the related mechanical properties at different rotation speeds in-depth, which can provide insight into experimental and theoretical foundations for achieving high-quality bonding of Al-alloy T-joints via the SSFSW

Materials and Methods

Results and Discussion

Rotation Speed Effect on the Surface of SSFSW T-Joints

Conclusions