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A Lifetime of Research in Creep, Superplasticity, and Ultrafine‐Grained Materials
Author(s) -
Langdon Terence G.
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201900442
Subject(s) - superplasticity , materials science , creep , climb , grain boundary sliding , metallurgy , slip (aerodynamics) , grain size , grain boundary , dislocation , flow stress , dislocation creep , composite material , strain rate , alloy , microstructure , thermodynamics , physics
A long‐term career at the University of Southern California, followed by an appointment at the University of Southampton, provided an opportunity to conduct extensive research into the flow behavior of polycrystalline metals. Initially, research is conducted on creep properties at elevated temperatures and it is shown that solid solution metallic alloys exhibit transitions in creep behavior with dislocation climb and viscous glide as the dominant rate‐controlling mechanisms. There are transitions between climb and glide with increasing stress and also a breakaway from the glide process at high stresses. These transitions are predicted theoretically and the results are in excellent agreement with the experimental data for a wide range of alloys. Attention is directed to the process of superplasticity and it is shown that the flow occurs by grain boundary sliding with accommodation by a limited amount of intragranular slip. Separate rate equations are developed for sliding in coarse‐grained materials and in superplastic materials where the grain sizes are generally <10 μm so that flow occurs without the development of any subgrains. Finally, attention is directed to the properties of ultrafine‐grained materials having submicrometer or nanometer grain sizes produced through the application of severe plastic deformation.