Anisotropic mechanical properties of porous copper fabricated by unidirectional solidification

Porous copper whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a mixture gas of hydrogen and argon. The porosity depends on the melting temperature of copper melt, while the orientation of the pores is controlled by the freezing direction. The anisotropy in the uniaxial tensile behavior of the porous copper is examined. The ultimate tensile strength and the yield strength of the porous copper with the cylindrical pores orientated parallel to the tensile direction decrease linearly with increasing the porosity. For the porous copper whose pore axes are perpendicular to the tensile direction, the ultimate tensile strength decreases significantly with increasing the porosity at low porosity, while the yield strength reaches a maximum at a low porosity and then decreases with increasing the porosity. These results are explained in terms of the stress concentration induced in the vicinity of the pores during tensile deformation.