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Alloy Design of Ordered Intermetallics†
Published online by Cambridge University Press: 28 February 2011
Abstract
Ordered intermetallics based on aluminides and silicides constitute a unique class of metallic materials possessing promising high-temperature properties. However, brittle fracture and poor ductility have limited their use as engineering materials in most cases. During the past ten years extensive research has been conducted on ordered intermetallics. As a result, significant progress has been made in identifying various causes of brittle fracture, and their relative importance in different ordered alloys. In some cases this understanding has helped achieve dramatic improvements in ductility. We review here three different classes of brittle fracture in ordered intermetallics and discuss the results in terms of model alloy systems chosen from each class. Ni3A1 and NiAl are discussed as prototypical ordered alloys prone to intrinsic intergranular brittleness. They are used to review our current understanding of intrinsically weak grain boundaries and the mechanisms by which boron is thought to suppress intergranular fracture. Next, FeAl and Fe3A1 are discussed as examples of ordered intermetallics that are susceptible to environmental embrittlement at ambient temperatures. Recent discoveries in these two alloy systems are reviewed with special emphasis on some of the rather interesting but subtle effects of test environment. Finally, A13X type intermetallics (A13 Sc, Al3Ti-base, and Al3 Zr-base alloys) are discussed as examples of ordered alloys that have high symmetry (L12 structure), are relatively soft, yet cleave transgranularly with very little ductility. In all these cases, experimental results are compared with theoretical calculations.
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- Copyright © Materials Research Society 1991
Footnotes
Research sponsored by the Division of Materials Sciences, U.S. Dept. of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.
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