Obtaining good ductility in an FeAl intermetallic

Abstract

Deformation and fracture mechanisms leading to tensile failure have been examined in a mechanically-alloyed and a recrystallized Fe–40Al intermetallic. It is shown that tensile failure begins by the initiation of a small crack near the sample surface at a given level of strain, and crack propagation occurs rather quickly thereafter such that the total strain at failure is only slightly larger than the crack initiation strain. Crack propagation is initially slow, and affected by the test environment, and later it is faster and unaffected by test environment. Deformation localizes into slip bands and crack nucleation takes place easily, at a small strain, in the recrystallized material of large grain size. In the as-extruded material, deformation remains homogeneous under the influence of the small distributed particles, and crack initiation over a scale of many grain dimensions is slow. Possibilities for further ductility improvements by microstructure control are discussed.