Weak boundary enabled tensile ductility in dealloyed porous Fe alloy

Abstract

Dealloying has emerged as a new route to the synthesis of porous or nanoporous materials for a variety of novel structural/functional applications. However, dealloyed (nano-)porous metals are notoriously brittle and often fracture catastrophically in bending or tension, which is detrimental to their applications. In this paper, we report that under tension, the irreversible fracture strain (εi) of a macroscopic porous Fe(MnCr) alloy prepared by liquid metal dealloying can be enhanced from nearly zero to 4.1 % by introducing weak domain boundaries, while previous samples with homogeneous (nano-)porous structure usually fracture at εi below 1.0 %. Tensile ductility is enhanced only if the mean domain size (D¯) is not too much larger than mean ligament diameter (L¯), evidenced by the dramatic increase in εi as D¯/L¯ decreases from ∼24 to ∼7. The “ductile” deformation of these materials is associated with the diffuse failure under tension, arising from the promoted nucleation of micro-cracks and the crack deflection or branching along weak domain boundaries at lower D¯/L¯. This strategy might also apply to other (nano-)porous materials self-organized in dealloying or fabricated by other methods.