Microstructural evolution and magnetic properties of pressureless-sintered nanosized iron prepared by a facile combustion-based route

Abstract

High-activity iron nanopowders were prepared through a facile combustion-based route, combining solution combustion synthesis and hydrogen reduction. The as-synthesized iron nanopowders were densified by pressureless sintering. The densification behavior, microstructure, mechanical properties and magnetic properties of the iron bulk sintered at different temperatures were studied in detail. At a low sintering temperature of 700 °C, the relative density of the sintered iron reaches 97.3%, because the iron nanopowders exhibit a low sintering activation energy of 123 KJ/mol. The iron bulk sintered at 700 °C exhibits relatively regular equiaxed grains with an average grain size of 0.45 μm, and has a maximum tensile strength of 510.1 MPa, a high microhardness of 201.9 HV, and a saturation induction of 1.75 T. As the sintering temperature increases, the grain size and magnetic properties of the sintered iron enhance, while the mechanical strength decreases. For the sintered iron prepared at 1300 °C with the average grain size ~ 80.9 μm, the saturation induction value reaches 1.78 T and the tensile strength is 334.9 MPa.