Improving the structure-property of aluminum alloy friction stir weld by using a non-shoulder-plunge welding tool

Abstract

In order to improve the joint performances by controlling the thermal effect of tool shoulder, a non-shoulderplunge (NSP) welding tool is utilized to conduct friction stir welding (FSW) of an Al-Mg aluminum alloy in this paper. Sound FSW joint is successfully produced by using the NSP welding tool. In contrast to conventional FSW (C-FSW), the thermal effect of tool shoulder is effectively reduced by NSP-FSW, leading to a significant size reduction of shoulderaffected zone in the joint. Besides, the NSP-FSW joint shows finer grain structures in the stir zone and thermo-mechanically affected zone, and exhibits lower extents of grain coarsening, dislocation polygonization, and particle dissolution in the heat-affected zone. Hardness maps show that the softening region width of NSP-FSW joint is only nearly half that of C-FSW joint and the NSP-FSW joint exhibits higher hardness in the heat-affected zone than C-FSW joint. The tensile test results indicate that the joint efficiency is improved from 89 % of C-FSW joint to 97 % by the NSP-FSW process.

Impact of shoulder concavity on non-tool-tilt friction stir welding of 5052 aluminum alloy

“…During the FSW of cold-worked aluminum alloys, the welding heat enables annealing and recovery to take place, and hence induces the formation of softening region with lower hardness than BM [16][17][18]. Since some strength recovery has occurred in the nugget zone and thermo-mechanically affected zone due to the grain refinement strengthening and strain strengthening effects, as commonly confirmed in the FSW of other non-heat treatable aluminum alloys [2,6,9], the joints all have the lowest hardness zones at the HAZs. The lowest hardness zones of 0-and 5-joints are located at the HAZ adjacent to pin periphery, while that of the 10-joint is moved outward to a further location from the weld center.…”

“…Compared with the flat shoulder, the concave shoulder provides larger escape volume for the displaced material from the tool pin; thus, it facilitates the reduction of weld flash [7,8]. Furthermore, in contrast to the conventional FSW, the NTT-FSW process using concave-shouldered tool has been demonstrated to be able to reduce the shoulder thermal effect and improve the joint properties [9].…”

Effect of Shoulder–Workpiece Interference Depth on the Quality of Friction Stir Welding of AA7075-T6 Aluminium Alloy

“…If the shoulder-WP interference is too high or too low, weld surface defects such as groove, flash and internal defects such as tunnel or void are more prone to be formed in the weld line. Actually, the worth of shoulder-WP interference reflects the scope of interaction between tool shoulder and WP thereby on the heat generation that effects on welding quality [17]. Derazkola et al [2] investigated the influence of shoulder plunge depth (SPD) on the mechanical properties of FSW of A441 AISI steel with AA1100 aluminium alloy.…”