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

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.

Effects of FSW Tool Plunge Depth on Properties of an Al-Mg-Si Alloy T-Joint: Thermomechanical Modeling and Experimental Evaluation

“…This phenomenon, known as stirring action, provides valuable information about the internal defect formation [ 56 , 57 , 58 ]. The controlling stirring action during FSW of the T-configuration is essential to produce a sound joint [ 3 , 19 , 36 , 59 ]. The material velocity can change the share of the flange in the welding area.…”

“…The value of β is defined between 0 and 1, where 0 is used for a nonmixing situation, and 1 is used for a well-mixed situation. The percentage of heat transferred into the workpiece is related to the thermal conductivity, density, and heat capacity of both the tool and workpiece material and is calculated by [35]: γ = kρC p workpiece kρC p tool + kρC p workpiece (12) The heat flux continuity of the shoulder-workpiece interface is presented as [36]:…”

Thermo-Mechanical Simulation of Underwater Friction Stir Welding of Low Carbon Steel

“…In Equation (17), ( ) is the effective strain rate, Q denotes activation energy, and R is universal gas constant [ 51 ]: where ε ij is the strain rate tensor [ 53 ]: …”

The Feasibility of Static Shoulder Friction Stir Welding in Joining Dissimilar Metals of Al6061 and Ti6Al4V

“…Achieving high-strength dissimilar joints requires experimentation with effective FSW process conditions to minimize material mixing and processing temperature [8,9]. Several studies have explored the influence of process parameters, such as tool offset [10], welding speed [11], rotational speed [12], and the number of multi-passes [13,14], on IMC formation in Al-Ti FSW joints. Li et al [15] observed poor joint strength due to massive IMC formation from Al and Ti intermixing.…”