Evidence of a thin sheet toughening mechanism in Al−Fe−X alloys

Abstract

A toughening mechanism, dubbed thin sheet toughening, is proposed for improving the fracture resistance (KIC and tearing modulus) of powder-metallurgy alloys of limited ductility. The basis of this approach is the recognition that internal delamination of thick-section components or cracked specimens into thin sheet ligaments in the fracture process zone leads to a drastic reduction in triaxial stresses, with the consequence of enhancing the critical fracture strain, fracture toughness (KIC orJIC), and tearing modulus. Theoretical analyses indicate that a factor of\(\sqrt 3 \), increase in theKIC value, and even greater increases in the tearing modulus are possible for idealized conditions. The predicted results are compared with experimental results of tensile,KIC, andJ tests conducted on four powder-metallurgy Al−Fe−X alloys at 25 and 316°C. The comparison reveals that thin sheet toughening is a contributor to the highKIC value observed in a state-of-the-art Al−Fe−V−Si alloy. Increasing the critical strain to fracture is also shown to be a possible method to improve the fracture toughness of Al−Fe−X alloys, independent of the thin sheet toughening effect.