A novel copper surface modification approach based on pinless friction stir surface processing technique with ultra-low heat input

Improving the wear and corrosion performances of widely employed copper and its alloy components can effectively extend their service life. In this study, a novel copper surface modification method based on the friction stir surface processing (FSSP) technique was achieved. Subject to FSSP with pinless tool and low heat-input process parameters (including a minimal axis tilt and extremely low rotational speed), the modified copper surface exhibited enhancement rates of 34.25 % in hardness and 44.76 % in tensile strength , and improved high wear and corrosion resistance characteristics. The research suggests that the primary reasons for the enhanced surface properties are the grain refinement strengthening effect and the rapid formation of a passive film. Additionally, the ultra-low heat input resulted in the preservation of numerous dislocation tangles and incomplete dynamic recrystallization in the modified region, which represented a microstructural evolution mechanism distinct from the traditional friction stir processing. This work provides a reference for a low-energy-consumption and easily achievable approach for enhancing the surface properties of metals. • A novel copper surface modification approach based on FSSP with pinless tool and ultra-low heat input was proposed. • The modified surface exhibited enhancements of 34.2% in hardness and 44.8% in tensile strength to copper substrate. • The hardened surface caused by fine grain strengthening resulted in high wear resistance of the modified surface. • The fast passivation film caused by multi grain boundaries improved the corrosion resistance of the modified surface. • The microstructure evolution was dominated by incomplete dynamic recrystallization under FSSP with ultra-low heat input.

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