Enhancement of Fracture Properties of Wustite by Precipitation

Abstract

Both the fracture‐initiation energy, γ i , and the fracture strength, σ f , of 99.5% dense wustite (grain size 23 μm) were substantially increased by (1) precipitating coherent‐coplanar Fe 3 O 4 , and (2) decomposing the wustite eutectoidally to α‐Fe+Fe 3 O 4 , forming a continuous α‐Fe network at the former wustite grain boundaries. The increase in γ i , and σ f resulting from the presence of 13 vol% Fe 3 O 4 in wustite was attributed to the difference in cleavage habits between the precipitates and matrix and to crack‐front pinning. The continuous α‐Fe network increased the fracture stability in that fracture was not catastrophic but progressed in steps. The improvement in γ i and σ f was attributed mainly to the plastic work in fracturing the α‐Fe.