Creep behavior of a cryomilled ultrafine-grained Al–4% Mg alloy

• Published in: Journal of materials research Vol. 15; no. 10; pp. 2215 - 2222
• Main Authors: Hayes, R. W., Tellkamp, V., Lavernia, E. J.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.10.2000
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.2000.0318

The creep behavior of a cryomilled ultrafine-grained Al–Mg alloy was examined. The grain size ranged from 300 to 400 nm. The stress exponents ranged from 7.2 to 7.4. The apparent activation energy for creep, 83.7 kJ/mol at 27.5 MPa and 77 kJ/mol at 38 MPa, agreed well with the activation energy for grain boundary diffusion in aluminum. Transmission electron microscope analysis following creep at 300 °C to approximately 0.2% strain in 1411 h revealed the grain size was unchanged from its as-extruded size indicating significant thermal stability of this material at relatively high fractions of the melting temperature. The creep resistance of the Al–Mg alloy was rationalized in terms of an attractive interaction between grain boundary dislocations and incoherent particles within the boundary region, which suppressed grain boundary deformation. The grain boundary particles also led to high thermal stability by exerting a Zener pinning force on the grain boundaries, thus inhibiting grain growth at high temperatures.