The influence of structural state on the mechanical and tribological properties of Cu-Al-Si-Mn bronze

Introduction. Electron beam additive manufacturing (EBAM) is a promising method for producing new alloys with unique properties. At the same time, existing problems with obtaining a high-quality structure require a search for a technical solution that ensures grain refinement and the formation of a more homogeneous microstructure. For strain-hardened copper alloys, severe plastic deformation (SPD) methods are effective ways to control their structural state and mechanical properties. Currently, the effect of severe plastic deformation on the structure, mechanical, and tribological properties of Cu-Al-Si-Mn bronze, which is promising for industrial application, has not been studied. The aim of this work is to study the relationship between the structural state formed as a result of severe plastic deformation and the mechanical and tribological properties of Cu-Al-Si-Mn bronze samples. The paper studies samples of Cu-Al-Si-Mn bronze, made from bronze (3% Si-1% Mn) wires and commercially pure aluminum using multiwire electron beam additive manufacturing. For targeted changes in structure and properties, the resulting additively manufactured blanks were subjected to severe plastic deformation. Multi-axial forging and rolling were used as SPD methods, aimed at significant grain refinement and increased strength characteristics. The work uses such research methods as transmission electron microscopy (TEM) for a detailed analysis of the submicron structure after SPD, X-ray diffraction (XRD) to identify the phase composition of the alloy, tensile tests to determine key mechanical properties such as tensile strength, yield strength, and percentage of elongation, microhardness measurements to assess the hardening of samples using Vickers loads, confocal laser scanning microscopy (CLSM) for three-dimensional analysis of the surface topography and studying the morphology of worn surfaces, and dry sliding friction tests to assess the wear resistance of the material and the friction coefficient in the absence of lubrication under specified loads and sliding speeds. Results and discussion. Based on the data of transmission electron microscopy, it was found that the use of multi-axial forging and rolling led to significant changes in the structure of the material, as well as its phase composition. Based on the X-ray diffraction analysis, it was revealed that severe plastic deformation contributed to the deformation-induced dissolution of the γ- and β-phases. The results of tensile tests showed that the highest strength is achieved after intense plastic deformation by rolling, after multi-axial forging. SPD by multi-axial forging and subsequent rolling led to an increase in the microhardness of bronze. The results of tribological tests showed that SPD contributes to a decrease in the friction coefficient (FC) compared to the material in the printed state. Heat treatment of samples after SPD led to an increase in FC and an increase in fluctuations in its value. SPD by multi-axial forging and subsequent rolling contributes to a significant increase in the wear resistance of samples under dry sliding friction conditions. Low-temperature annealing after SPD leads to a decrease in the wear resistance of deformed samples. Thus, the use of SPD makes it possible to increase the strength and wear resistance of bronze samples of the Cu-Al-Si-Mn system.