Mechanical characterization and modeling of graded porous stainless steel specimens for possible bone implant applications

A detailed experimental and numerical investigation was performed on graded porous stainless steel preforms for bone implant applications in order to understand the variation of mechanical properties along the graded direction. A simple powder metallurgy methodology was employed to fabricate preforms whose surfaces were later densified with a specially designed densification tool. Homogeneous preforms without densification were tested under uni-axial compression for their stress–strain response. The stress–strain responses of the preforms having various porosity levels were used in numerical modeling in an attempt to understand the porosity gradient generated during the densification process. Micro-indentation experiments were also conducted to determine the variation of Young’s modulus values along the densified layer of preforms. Numerical results indicated that the equivalent plastic strain correlated well with the porosity gradient. In addition, it was found that the diameter of the ball used as a densification tool could significantly influence the porosity gradient of the preform.