چكيده به لاتين
Al-Cu friction stir welding has not yet been sufficiently developed and used. Because for metals with high thermal conductivity, such as copper, it is difficult to obtain a weld without defects. In this study, FSW process parameters optimization method have been used to achieve high quality joints with better tensile and electrical properties simultaneously.To perform the experiments and to expand the mathematical model of regression by Design Expert software, the CCD multiple response method was used with consideration of two FSW parameters (tool rotation speed and tool transverse speed), five levels and twelve runs. Besides validating the predicted models, variance analyzes show that the interaction of the two parameters together has the greatest effect on the desired properties. Microstructure analysis revealed that the compound of AlCu, Al2Cu, and Al4Cu were observed in cross section of the joints, and the amount of these intermetallics increased with increasing the ratio of tool rotational speed to tool transverse speed (W/V). The most common welding defects were detected in joints with high and low W/V, which reduced the tensile properties and increased the electrical resistance of the joints. Based on expanded models, the combination of 950 rpm and 85mm/min parameters led to proper joints, with high tensile strength and high elongation as well as low electrical resistance simultaneously. Comparison of the test result performed at the optimum point with the predicted result of the software for the optimum point, corresponded to 90.7% confidence and showed the high validity of the fit model for the experiments. The tensile strength and the elongation of optimum joint were 65% and 6.19% of 2024 aluminum base metal, respectively. Also electrical efficiency of optimum joint was 88%. The hardness of the joints was investigated in the ratio of high, medium and low W/V parameters. Finally the use of Zn foil as an interlayer increased the tensile properties of Al2024 to pure copper.
