Effect of Space Holder on Porosity, Structure and Mechanical Properties of Al Processed via Powder Metallurgy

In recent times, porous materials have been gaining greater interest due to its potential applications such as energy, light weight structural components, scaffolds for bio-applications, insulators, etc. The present work aims at investigating the effect of different space holder materials (NaCl, urea and sugar) on porosity, microstructure and properties of aluminum (Al). In particular, the space holder material amount was fixed at 30 vol% to prepare porous Al. Dissolution sintering process (DSP) and sintering dissolution process (SDP) have been used to prepare the porous Al. Depending on type of space holder and processing technique, the volume fraction of porosity of Al processed via DSP varied in the range of 22.75% to 34.76% and SDP resulted porosity from 26.17 to 34.16%. The Al obtained by DSP was predominantly characterized with porous structure without much interconnected pores. On the contrary, more amount of pores and interconnected porosity was observed in the Al samples produced by SDP. The porous Al processed via DSP exhibited better compression properties (yield strength: 31.0–49.5 MPa, compression strength: 41–161.5 MPa, %Strain: 11.25–46.73, elastic modulus: 0.26–1.42 GPa) than SDP Al (its compression properties measured as: yield strength: 23.5–32.5 MPa, compression strength: 27.5–107.0 MPa, %Strain: 5.79–34.82, elastic modulus: 0.52–1.59 GPa). Such differences in the mechanical properties of porous Al can be attributed to pore structure and residual amount of space holder. The residual space holder content varied between 1.72 and 14.65% for the porous Al processed under different conditions. Overall, this study demonstrates that Urea(spherical) and sugar are preferable as space holder materials to prepare porous Al via DSP and SDP, respectively.