In this research effort, we explore the use of a donor material to help heat workpieces without wearing the tool or adding more heat than necessary to the system. The donor material would typically be a small piece (or pieces) of material, presumably of lower strength than the workpiece but with a comparable melting point. The donor, a sandwich material, is positioned between the tool head and the material to be welded, where the tool initially plunges and heats up in the same manner as the parent material that is intended for welding. The donor material heats up subsequent to tool penetration due to friction and as a result heats up the material beneath it. This preheating technique softens the harder parent material, which helps to minimize tool wear and produce better weld performance. The goal is to investigate the use of the donor material as a preheating technique that minimizes wear and tear on the tool head without negatively impacting the structural properties of the weld. To demonstrate the donor material concept, a combination of Cu-Al, Cu-1045 Carbon steel (CS), and Al-1045 CS sets of donor and parent materials were used in the simulation, in addition to control samples Al-Al and CS-CS. We simulated two thicknesses of donor material 25 and 50% of the parent material thickness, respectively. The simulation suggests that the donor material concept generates phenomenal results by reducing the temperature and axial forces for the friction stir welding of aluminum AA6061 and carbon steel 1045. It also assists downstream during welding, resulting from frictional mechanical work which is converted into stored heat.
In this research, Copper (Cu) donor material assisted friction stir welding (FSW) of AA6061-T6 alloy was studied. Cu assisted FSW joints of AA6061-T6 alloy were prepared at a constant tool rotational rate of 1400 rpm and various welding speeds at 1 mm/s and 3 mm/s. The Cu donor material of different thickness (i.e., 20%, 40%, and 60%) with respect to the workpiece thickness was selected to assist the FSW joining at the plunge stage. It is observed that the downward force generated in the FSW process was gradually decreased after introducing Cu donor material with incremental thicknesses with respect to workpiece at the plunge stage. Post-weld analysis was characterized in terms of microstructure, and mechanical properties. The results of microstructure analysis at the stir zone (SZ) show the formation of ner grains due to dynamic recrystallization and plastic deformation. Microhardness tests reveal that the hardness decreased from the base metal (BM) to the SZ across the heat affected zone (HAZ) and thermo-mechanically affected zone (TMAZ). The lowest value of hardness appeared in the TMAZ and HAZ where tensile failure occurs. With increasing welding speed, the average hardness in the SZ decreased due to lower heat input and faster cooling rate. Tensile test plots show no signi cant change in ultimate tensile strength with or without Cu donor material. Fractography of tensile tested samples shows both ductile and brittle like structure for given welding parameters. This proposed work of FSW with Cu donor material is promising to increase tool life due to the decrement of the downforce during plunge and throughout the welding stage. Meanwhile, the inclusion of donor material did not compromise the weld quality in terms of the mechanical properties and micro-hardness. 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) processes. To investigate this research question, Copper (Cu) was adopted as the donor material to assist the FSW of Al 6061. Through comparing experiments with and without donor material inclusion in FSW, it was found that the donor material induces drastic decreasing in downward force during FSW processes, which will increases the lifetime of the FSW tools. Meanwhile, the post-weld analysis identi ed no signi cant change occurred in the mechanical properties and microstructure of the welded joints, which is desired for industrial applications. The implementation of the donor material is promising to increase the lifetime of the FSW tools without compromising the mechanical properties FSW joints. The proposed approach is also economical for industrial application due to its effective potential to enhance the life of friction stir tools. What is novel? In theory, in experimental techniques, or a combination of both?This paper presents the novel experimental approach of introducing a Copper (Cu) donor material during the initial stage of friction sti...
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...
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