SHEARING AND TOUGHENING MECHANISMS IN AN RSP RECYCLED ALUMINUM-ALLOY

The shear fracture behavior was investigated using both smooth and cir cumferentially-notched bars under uniaxial tension in a temperature ra nge of 193 K-423 K and a strain rate range of 10(-5)-1 s(-1), and the fracture toughness was evaluated using circumferentially-cracked cylin drical specimens tested al room temperature, for an Al alloy recycled via rapid-solidification processing (RSP). An analytical procedure was performed to make corrections on the hydrostatic stresses in the neck ed region of the smooth specimen. The results indicate that a pure she ar fracture occurs only for the as-extruded alloy in plain tension at intermediate temperatures and relatively low strain rates, and the int erfacial delamination is associated with both the shear fracture in pl ain tension and the local shearing in notch tension. A constraint-rele asing mechanism is proposed to account for the combined mechanical and metallurgical conditions under which the present shear fracture is ev ident. This mechanism is attributed to increase appreciably the alloy' s resistance to stable crack growth but is not effective in affecting the plane strain Fracture toughness. (C) 1997 Acta Metallurgica Inc.