The mechanical behavior of a cryomilled Al-10Ti-2Cu alloy

The mechanical behavior of a cryomilled Al-10Ti-2Cu (wt.%) alloy has been s tudied by performing uniaxial tension tests at temperatures ranging from ro om temperature to 525 degreesC, Elastic-nearly perfectly plastic stress-str ain behavior is observed at all temperatures. Tension-compression asymmetry of the room temperature yield stress is also observed. Those characteristi cs are in agreement with those recently reported in the literature for sing le-phase NC materials. The flow stress (700 MPa at room temperature) decrea ses dramatically with increasing temperature. Testing of material following thermal exposures suggests that microstructural coarsening alone cannot ac count for the decrease in strength with increasing temperature. From a coar sening standpoint, this material appears to be very thermally stable. The d uctility is influenced by several factors. Low levels of internal porosity along with the presence of fine oxide and carbide dispersoids contribute to lower ductility. The absence of work hardening exhibited by the Al-10Ti-2C u also leads to reduced strain to failure. The features observed on fractur e surfaces suggest that fracture occurs by the nucleation and growth of voi ds at particle-matrix interfaces. Evidence of fracture along prior powder p article boundaries is present as well. The microstructure consists primaril y of regions containing grains measuring in the range 30-70 nm. Large grain ed regions consisting of nominally pure Al ranging in size from 300 to 500 nm are also present. No evidence of dislocation activity within either the fine or large grained regions can be found in the as extruded material. Spe cimens deformed at room temperature and 93 degreesC reveal evidence of disl ocation activity within the large grain regions. Dislocation configurations suggest an Orowan bypass mechanism. No dislocations are found within the 3 0-70 am size grains following tensile deformation. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.