Evolution of microstructure, microhardness and surface roughness of Al alloy thin-walled tube during flaring process

Abstract

Flaring forming has been widely utilized in connecting tubes, fluid pipe circuit components and flight fairings. Surface quality of the flared inner wall significantly affects the connection properties and service reliability. However, the surface microstructure, hardness and roughness of flared thin-walled tubes have long lacked corresponding characterization and correlation analysis. In the present study, wear mechanism of a 5052 Al alloy flared tube is analyzed based on multi-scale characterization. Furthermore, the impact of flaring process parameters including spindle speed, feed rate and holding time on the surface roughness is investigated by considering the evolution of microstructure and microhardness. The results reveal that adhesive wear is the main wear mechanism in the flared tube, accompanied by a small amount of abrasive wear. The effect of process parameters on dynamic recrystallization (DRX) and grain orientation are also analyzed in detail. Based on ANOVA analysis, the spindle speed is found as the most crucial controllable parameter affecting the surface roughness. The feed rate is the second important parameter, while the holding time is found to be insignificant. Simulation and experimental results indicate that with the increase of strain, surface roughness first increases and then decreases. This non-monotonic trend is associated with the evolution of strain (strain rate, strain path, etc.) and microstructure (DRX, texture, hardening, etc.).