In situ and tomographic characterization of damage and dislocation processes in irradiated metallic alloys by transmissi
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Bai Cui Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA; and Department of Mechanical and Materials Engineering, University of Nebraska, Lincoln, Nebraska 68588, USA
Ian M. Robertson College of Engineering, University of Wisconsin, Madison, Wisconson 53706, USA (Received 14 October 2014; accepted 2 January 2015)
Progress toward combining time-resolved experiments with periodic three-dimensional analysis of the evolved microstructural state has been made recently. In situ electron microscopy is used to observe in real time the development of irradiation defects and the influence of these defects on dislocation behavior. Three-dimensional characterization provides information on the true spatial distribution of defects and clarifies effects of the free surfaces in thin films. This quasi-four dimensional analysis approach has been applied to understand the formation of channels in irradiated alloys, the depth distribution of ion damage in an electron transparent foil, and the dislocation channel interactions with grain boundaries. The new insight obtained from these experiments is highlighted and contrasted with findings from simulations.
I. INTRODUCTION
The degradation of mechanical properties of metals by irradiation with high-energy particles, neutrons, protons, or ions has been investigated extensively.1–3 It has been shown that the irradiation damage leads to a loss of ductility, an increase in the yield strength and hardness values, and the appearance of a distinct yield point.4–8 Irradiation can also lead to secondary detrimental effects such as susceptibility to stress corrosion cracking and lower failure strain during creep deformation.9–11 This degradation of mechanical properties has important implications in the monitoring of current nuclear reactors as well as in the development of the next generation of reactor structural materials.12,13 Advances in both areas require a fundamental understanding between the short- and long-term microstructural changes induced by irradiation damage and their effects on the mechanical properties. A persistent challenge in understanding the effects of irradiation damage is the temporal and spatial scales involved. The initial impact of high-energy particles causes damage initiation at the picosecond timescale Contributing Editor: Khalid Hattar a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.14 1202
J. Mater. Res., Vol. 30, No. 9, May 14, 2015
http://journals.cambridge.org
Downloaded: 05 Jun 2015
and at atomic length scales.14,15 The degradation of mechanical properties, however, can continue to evolve over the course of decades and involves interactions spanning multiple grains.13 As the conditions encountered in application cannot be replicated in a single experiment, the development of accurate simulations is vital. This includes computer simulations as well as experiments capable of simulating the effects experienced by materials in application. T
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