Influence from Size and Morphology of Mn₅Si₃ on Wear Resistance of Cu-Zn-Al-Mn-Si Alloys

In this study, the microstructure, hardness, and wear resistance of two kinds of copper alloy are demonstrated to be affected by both composition, annealing temperature, and phases present with a sliding block-on-ring test, where the ring is 316 stainless steel. With a higher content of Zn, the solubility of Mn and Si would decrease, resulting in increased volume fraction of the hard ω-Mn₅Si₃ phase (with a high nanoindentation hardness of 12.9 GPa). Moreover, the higher contents of Mn and Si lead to the formation of large primary polyhedron Pω-Mn₅Si₃ cylinders during solidification. With the help of two-stage forging, the primary polyhedron Pω-Mn₅Si₃ grow along [0001], enabling the large primary Mn₅Si₃ cylinders all parallel to each other. This special microstructure could significantly improve the wear resistance in comparison with the samples with a microstructure containing only small and randomly oriented precipitates. Such parallel primary polyhedron Pω-Mn₅Si₃ cylinders can act as reinforcements to grab the matrix, effectively improving the wear resistance.