Microstructural investigations of an ultrafine eutectic Fe83Ti7Zr6B4 alloy reveal that spherical eutectic colonies are composed of nanoeutectic areas which are encapsulated by submicron eutectic areas indicating length-scale heterogeneity of lamellar structure. Furthermore, formation of the wavy and discontinuous shear bands indicative of dissipation of the shear stress are possibly caused by a rotation of the eutectic colonies along the submicron eutectic areas during deformation, leading to developing typical dimples on the fracture surface. The rotation of the eutectic colonies containing the length-scale heterogeneity is proposed to be responsible for macroscopic plasticity of the ultrafine eutectic Fe83Ti7Zr6B4 alloy.

A Ni–8Zr high strength ultrafine eutectic-dendrite composite with large plasticity has been developed in the Ni–Zr binary eutectic system. The excellent mechanical properties are attributed to the specific heterogeneous microstructure with distinctly different length scales, i.e., micrometer-size ductile dendrites combined with an ultrafine eutectic matrix. The plastic deformation mainly proceeds through a shear banding mechanism. However, there is no significant shear localization due to the constraint effect of ductile solid solution Ni phases including dendrites and/or alternating lamellar layers. Furthermore, excessive shear stress and accumulated shear strain can be effectively released and accommodated by delocalization and multiplication of shear bands.