Effects of particles and solutes on strength, work-hardening and ductile fracture of aluminium alloys

Abstract

The influence of particles and solutes on the strength, work-hardening behaviour and ductile fracture of four different aluminium alloys in the as-cast and homogenised condition is investigated in this paper. These alloys contain different types and volume fractions of particles, i.e. constituent particles and dispersoids, in addition to elements in solid solution. Tensile tests on smooth and notched axisymmetric specimens are performed to determine the work-hardening curves and the ductile fracture characteristics of the alloys. A laser-based extensometer is used to continuously measure the logarithmic strain to failure in the minimum cross section of the specimens. Finite element simulations of the test specimens are used to determine the work-hardening curves to failure. Both the J2 flow theory and the Gurson model are used to describe the stress–strain behaviour of the materials, where the latter accounts for material softening due to void growth. The microstructure of the alloys is characterised by optical and scanning electron microscopy, and fractography is performed to investigate the fracture modes. While the damage and failure mechanisms are similar in the four alloys, the failure strain depends markedly on the stress triaxiality and the yield stress. The trend is that the failure strain decreases linearly with increasing yield stress for the investigated alloys.