Evolutions of microstructure and mechanical properties of copper/SS304L composite micro channels during micro rolling

Abstract

Manufacturing metallic micro channels is a critical issue in micro-electromechanical systems (MEMS), such as micro reactors, micro heat exchangers, micro heat sinks, and fuel cell bipolar plates. An ultra-thin metal foil rolling for the fabrication of micro composite channels was proposed in this study, which is able to improve product functions and reduce operational costs. Copper/SS304L composite foils after annealing at 900 °C were used to form micro channels under different rolling reductions (29.1%, 43.8% and 50.0%), in which the thickness of copper and SS304L are 0.3 mm and 0.1 mm, respectively. Accordingly, the microstructure evolution, material deformation behaviours and mechanical properties of the samples after micro rolling were investigated. From the characterisation of the micro channel region on the copper side, a double fibre texture is produced parallel to the rolling reduction, including a relatively strong <111> fibre and a weak <100> fibre. Moreover, a relatively strong <111> fibre and three weak <100>, <110> and α fibres along the rolling direction can be identified on the SS304L side. The hardness of copper and SS304L increases with the increase of rolling reduction, due to the strain-hardening effect for copper, and accumulated dislocation and formation of strain-induced α’ martensite for SS304L during micro rolling, respectively. It is noted that in the ridge region for all the samples, the left fillet is harder compared to the right fillet, indicating the asymmetry of material flow.