High strain rate embossing with copper plate

Embossed parts, that contain a number of features, are desired for a range of components, such as, heat exchangers, bipolar plates, micro-reactors, and micro-fluidics. A comparison of low strain rate embossing and high strain rate embossing was investigated in this study. High strain rate deformation at the embossed surface induced quatitatively different properties than those on a quasi-statically formed part. A commercial hand file was chosen as a simple and available die surface due to its high hardness and relatively fine features. Commercially pure copper (110) was embossed using four methods: quasi-static (static, low strain rate), magnetic pulse (MP, high strain rate), direct vaporizing foil actuator (direct VFA, high strain rate), and urethane-assisted vaporizing foil actuator (urethane VFA, high strain rate). Embossed depth, mechanical properties, and microstructure evolution were studied for both low strain rate embossing and high strain rate embossing. The results showed that generally better conformity to the die features and higher surface hardness were achieved with high strain rate embossing, in part because higher pressures could be developed with these methods. The study of the microstructure revealed that besides the grain size and shape change, significant twinning appeared along the deformed surface in high strain rate embossed parts. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were performed to study the resultant microstructure.