Densification and strength evolution in solid-state sintering Part I Experimental investigation

Prealloyed bronze (Cu-10Sn) powder and a mixed elemental steel (Fe-2Ni-0.9C) powder were evaluated for strength evolution during sintering. For the bronze powder, test samples were fabricated using a loose powder casting method, while the steel powder was formed by injection molding. In situ strength during sintering was measured using a bending fracture test. Primary focus was on measuring the effects of sintering temperature and time on in situ strength evolution. Sintering temperature had the most significant effect, but the strength underwent significant gains prior to densification. The results are explained by the competition among interparticler neck growth, densification, and thermal softening. Sinter strengthening is initially governed by interparticle bonding, followed by a contribution from densification at high temperatures. However, high temperatures also lead to significant strength degradation due to thermal softening. Densification is favored by the declining in situ strength associated with thermal softening at high temperatures.