Sintering Behaviour, Graded Microstructure and Corrosion Performance of Sintered Fe-Mn Biomaterials

Abstract

This article discusses the corrosion of sintered Fe-Mn alloys, as influenced by spatial variability in microstructure and composition. Materials of interest were manufactured by mixing an iron powder with 25, 30 and 35wt.% of manganese powder, pressing the mixtures in a die and sintering. Particles that the sintered materials were comprised of possessed ferritic/martensitic core regions and austenitic pheripheries. While the thickness of austenite shell seemed to increase with increasing Mn content for Fe-25Mn and Fe-30Mn materials, it appeared to fall to its lowest value for the Fe-35Mn material. The corrosion potential of a material exposed to Hank's solution increased with increasing Mn content for Mn-poorer materials but fell to its lowest value for the Mn-richest material. The fractal dimension of an electrochemical noise generated in corroding material was much lower than 1.5 for Mn-poorer materials but increased to the ''white noise'' value of 1.5 for the Mn-richest material. Corrosion rates of all materials were higher than those reported for homogeneous Fe-Mn alloys. It was concluded that while the Mn-richest material was very likely undergoing general corrosion, Mn-poorer materials suffered from galvanic interaction between particle cores and pheripheries and their corrosion was dominated by localized events.