Role of oscillation frequency and amplitude on the microstructure and properties of linear friction welded nickel aluminium bronze joints

Abstract This study explores the influence of oscillation frequency and amplitude on the quality of linear friction welded joints using as-cast nickel aluminium bronze. Welding was conducted at 30 Hz, 50 Hz, and 70 Hz oscillated frequencies and amplitudes of 1.5 mm, 2 mm, and 3 mm. The joint’s performance was thoroughly investigated through systematic analysis, including macrostructure examination, peak interfacial temperature measurement, microstructure evaluation, strain assessment, cooling rate determination, microhardness testing, and tensile property characterization. The width of the weld zone varied from 183 μ m to 297 μ m, and the thermomechanical affected zone (TMAZ) area ranged from 4.48 mm 2 to 14.79 mm 2 across different process parameters. In the parent material, the volume fraction of the β -phase was as low as 20.2%, contrasting with the dominant α -phase at 79.8%. The average grain size of the lamellar and globular α -phase mixture was 26.4 μ m. Notably, the weld zone exhibited extremely refined α -phase grains, with diameters less than 5 μ m in all cases. The volume fraction of the β ‘-phase increased significantly with higher frequencies, from 15.299% at 30 Hz to 26.98% at 50 Hz, peaking at 40.08% at 70 Hz, leading to varying k phases. This variation in microstructure had a substantial impact on mechanical properties. Tensile strength ranged from 503 MPa to 582 MPa, while ductility varied from 13.5% to 21.7%. Additionally, the hardness of the parent material increased from approximately 155 Hv to 260 Hv. This study demonstrates that controlling the oscillation frequency and amplitude in linear friction welding processes can yield consistent, high-quality welds in nickel aluminium bronze.