Cu donor material assisted friction stir welding of AA2024 and AA6061 dissimilar alloys: Effect on downward force, temperature profile, and mechanical properties

Abstract

In this research, the authors investigated copper (Cu) donor material assisted friction stir welding (FSW) of AA2024-T4 and AA6061-T6 aluminum plates of 6.35 mm thickness. FSW joints were prepared at optimized process parameters at a constant tool rotational rate of 1400 rpm and welding speeds at 1, 2, or 3 mm/s. The Cu donor material of 25% and 50% thickness with respect to the workpiece thickness were selected to assist the FSW joining at the plunge stage. During the welding processes, it was observed that the downward force generated in the FSW process was gradually decreased after introducing Cu donor material. Temperature pro les proved that the inclusion of copper donor material increased the temperature at the beginning of the welding process. Post-weld analysis was characterized in terms of micro-hardness and tensile properties of the welded joints. The experimental results revealed that defect-free joints could be obtained when placing high strength AA2024 alloy at the advancing side with 25% thick donor material. Micro-hardness test results indicated that the hardness decreased from the base metal (BM) to the stir zone across the heat affected zone (HAZ) and thermo-mechanically affected zone (TMAZ). The lowest hardness measurements occurred in the TMAZ and HAZ where tensile failure occurs. The maximum tensile strength improved by 130% with 25% Cu donor material as compared to aswelded condition. SEM Fractography images con rmed mixed modes of brittle and ductile fracture surface with tearing ridges and ner dimples after heat treatment. What Is Your Main Contribution To The Field?The main contribution in this research is on the novel and solid experimental approaches to examine whether donor material can assist friction stir welding (FSW) of dissimilar aluminum alloys. Copper (Cu) was chosen as a donor material due to its good thermal properties. FSW experiments were performed in two different groups: 1) as-welded condition (without Cu donor material) and 2) Cu donor material in assisting different weld con gurations. During the experimentation, it was identi ed that the inclusion of donor material decreases the downward force drastically. It is well known that, when the downward force decreases, the frictional coe cient and contact pressure will reduce, thus it lowers the tool wear. We also studied the temperature pro les using thermocouple in during FSW processes. The temperature measurements con rm that the donor material preheats workpieces in the plunge stage of FSW. The Cu material helps compensate the thermal properties difference between two work pieces, and maintain the equilibrium heat throughout the weldment. The defect-free welding joints were produced when the donor material thickness was 25% of the work piece thickness. Post-weld mechanical testing con rms that the mechanical properties including mechanical strength and micro hardness were not affected after using donor material. This novel idea of FSW assisted by donor material is promising for high volume welding in industrial application...

Fatigue Behavior of Rotary Friction Welding of Acrylonitrile Butadiene Styrene and Polycarbonate Dissimilar Materials

“…Therefore, this technology is frequently used to join metals or polymers [ 7 ]. Bhukya et al [ 8 ] investigated its effect on the mechanical properties, downward force, and temperature profile of an aluminum alloy using friction stir welding. The results revealed that low force was decreased after introducing the copper donor.…”