Process Parameters Optimization of Rotary Friction Welding of Silicon Bronze CuSi3Fe2Zn3 Alloy Using Response Surface Methodology

This study investigates the optimization of selected process parameters in the rotary friction welding (RFW) process of CuSi3Fe2Zn3 silicon bronze alloys using Response Surface Methodology (RSM) with tensile strength as the primary response. The effects of rotation speed, friction time and friction pressure were evaluated, and the steepest ascent method was applied to determine the best parameters. The results indicated that rotation speed and friction time were the most influential parameters for enhancing tensile strength. A maximum tensile of 424 MPa was achieved under conditions of 3300 rpm, friction time of 25 s, friction pressure of 0.5 MPa, forging time of 16 s, and forging pressure of 8 MPa. However, confirmation experiments exhibited noticeable variability, indicating limitations in process repeatability. Tensile properties, hardness evaluation, microstructural characterization, and thermographic analysis were conducted to assess the quality of the welded joints. Microstructural analysis revealed recrystallized equiaxed grains in the welding center zone, consistent with severe plastic deformation, while microcracks and microvoids were observed and likely contributed for failure during tensile testing. Despite grain refinement, a reduction in microhardness was detected, suggesting the influence of thermal softening mechanisms. Thermographic analysis indicated that the average temperature at the welding center zone reached 564 °C. In conclusion, RSM proved to be a useful tool for identifying trends and guiding process optimization. The results highlight the importance of process stability and control in achieving consistent performance in RFW of copper-based alloys.