The micromechanical properties of the structural phases in non-fluxed indurated titanomagnetite pellets

Abstract

Compressive strength is one of the strength metrics of indurated pellets in macroscopic tests and is governed by crack initiation and growth, typically through the pellet core where tensile stresses are highest. We used instrumented indentation to study local deformation processes and quantify microhardness, reduced modulus of elasticity, plasticity index, and creep for titanomagnetite/magnetite and titanohematite/hematite phases in the cores of non-fluxed indurated titanomagnetite pellets. SEM/EDS revealed grains composed of titanomagnetite and titanohematite containing minor Al, Mg, and V; the magnetite and hematite phases also contain minor Al and Mg. XRD indicated that the smaller the interplanar spacing and the unit-cell volume, the higher the microhardness of these structural phases. It was shown that the plasticity index for titanomagnetite/magnetite exceed that for titanohematite/hematite, while titanohematite/hematite exhibits lower creep; together, these results point to a greater propensity of the latter to accumulate internal stresses leading to microcrack formation.