The influence of texture on the elastic properties of ultrafine-grain copper

The connection between texture and elastic behavior of ultrafine-grain (250 nm) copper produced by severe plastic deformation is investigated. A previous study indicated that as-processed ultrafine-grain copper has a low elastic modulus (E = 115 GPa) which recovers the accepted value (128 GPa) after annealing above 150-200 degrees C. It was proposed that the low modulus was the result of non-equilibrium grain boundaries. In the current study we have found that the anomalous elastic behavior is likely to be the result of a deformation texture formed during processing. The texture was characterized by x-ray pole figure analysis, revealing preferred orientations of 10 x random. The orientation distribution function tvas calculated and incorporated into a Hill approximation of the elastic behavior. Experimental ultrasonic velocities were measured revealing anisotropy consistent with the predictions of the Hill approximation. After annealing above the recrystallization temperature (185 degrees C). texture analysis and acoustic velocity measurements showed isotropy was recovered. (C) 1998 Elsevier Science S.A.