Notch tensile testing as a measure of the toughness of aluminum alloys

Abstract

In the development of high strength aluminum alloys, sharp focus has been placed on toughness as well as on strength, stiffness, fatigue behavior, corrosion etc. In this paper the tension properties (the ultimate tensile strength σ UTS, the yield strength σ YS and the elongation) of various rapidly solidified and ingot-based aluminum alloys were examined and correlated with their notched tensile properties. Compiled data have shown that a linear relationship exists between the yield strength σ YS and the notch yield ration σ NTS/ σ YS (where σ NTS is the notch tensile strength); there is a poorer correlation between the ductility and the notch yield ratio. On the basis of linear elastic fracture mechanics, the linear relationship is extended to relate σ YS with K Ic. Under a given set of processing parameters, the extended equation K Ic = f( σ YS) could be utilized to indicate whether the toughness of an alloy (taking into account the related processing stepps) in any way encourages or discourages further development. Overall results indicate that rapidly solidified alloys are no better than ingot metallurgy alloys in terms of toughness and raise the question of why this should be so. One probable reason may be the presence of excess oxides in the form of stringers in the inadequately worked rapidly solidified and powder metallurgy alloys.