Microstructure and creep behaviour of an Osprey processed and extruded Al-Cu-Mg-Ti-Ag alloy

This paper reports the microstructure and creep behaviour of an Al-Cu-M-Ti-Ag alloy processed via Osprey forming and extrusion. The microstructure of the as-received extruded bars showed elongated grains towards the extrusion direction, which contained a fine substructure. Elongation to failure values of about 25% were obtained at test temperatures up to 400 degrees C and for strain rates ranging from 10(-4) to 10(-2) s(-1). In this temperature range, the mechanical behaviour of the alloy was similar to that of particle-strengthened aluminium alloys: (1) the apparent stress exponents of n = 17 and 7 were higher than that reported for most aluminium alloys; (2) the microstructure and the texture did not change significantly during tensile deformation. At temperatures higher than 400 degrees C, the elongated grains of the microstructure started to recrystallize into smaller grains and a maximum elongation to failure of 170% was observed at 520 degrees C and 10(-4) s(-1). Tensile tests performed at higher strain rates in this temperature range revealed a stress exponent of 4.5, which corresponds to a slip creep mechanism. (c) 2006 Elsevier B.V. All rights reserved.