Strengthening of lotus-type porous copper by ECAE process

Lotus-type porous copper with directional cylindrical pores was fabricated by unidirectional solidification in a pressurized hydrogen atmosphere. Improvements in microstructure and mechanical properties of the lotus-type porous copper by equal-channel angular extrusion (ECAE) were investigated using a die with a channel angle of 150°. The porosity decreases with increasing pass number, and decreases from 46% to 30% by four passes. It means that pore closure in the ECAE process is not significant. Both the specific compressive yield strength σ0.2%* and the Vickers hardness HV of the lotus copper increase with increasing pass number of ECAE. The ECAE processed porous copper shows improved σ0.2%* and HV comparable to those of the extruded nonporous copper. It is suggested that ECAE is a promising method to strengthen porous metals without significant pore closure.