简介:Preface
In nature most materials, such as rocks, ice, sand and soil, appear to be aggregates
composed of a set of crystalline elements. Similarly, modern society
is built on applications of metals, ceramics and other 简介:Preface
In nature most materials, such as rocks, ice, sand and soil, appear to be aggregates
composed of a set of crystalline elements. Similarly, modern society
is built on applications of metals, ceramics and other “hard materials”, which
also are polycrystalline. So are drugs, bones and trace particles relevant to
environmental matters, as well as many objects of artistic or archaeological
significance.
Remarkably, until recently, no nondestructive method existed for providing
comprehensive three-dimensional information on the structure and
dynamics of polycrystals at the scale of the individual elements (the grains,
subgrains, particles or domains). X-ray and neutron diffraction have been confined
to two limiting cases: powder diffraction, which averages over elements,
and diffraction performed on single crystals. Most real-world materials occur
as heterogeneous aggregates with substantial internal structure, and thus fall
between these two extremes. Local information has been provided by tools
such as optical, electron, ion beam and scanning probe microscopy. However,
these methods probe the near-surface regions only. Hence, the characterization
is only two-dimensional and prohibits studies of bulk dynamics.
Three-dimensional x-ray diffraction (3DXRD) is a novel experimental
method for structural characterization of polycrystalline materials. It is based
on two principles: the use of highly penetrating hard x-rays from a synchrotron
source and a “tomographic” approach to the acquisition of diffraction
data. Uniquely, the method enables a fast and nondestructive characterization
of the individual microstructural elements (grains and sub-grains)
within millimeter-to-centimeter-sized specimens. The position, morphology,
phase and crystallographic orientation can be derived for hundreds of elements
simultaneously, and the elastic and plastic strains can also be derived.
Furthermore, the dynamics of the individual elements can be monitored during
typical processes such as deformation or annealing. Hence, for the first
time, information on the interaction between elements can be obtained directly.
The provision of such data is vital if we are to extend our knowledge
beyond the current structural models.
The aim of this book is to give a comprehensive account of 3DXRD microscopy,
with a focus both on methodology and on applications. The methodology
is presented from a geometric/crystallographic point of view, but with
VIII Preface
sufficient details of algorithms and hardware to enable the reader to plan his
or her own 3DXRD experiments and analyze the resulting data. The main
applications are introduced by a short preamble, intended to motivate the
use of 3DXRD. To underline the prospects for 3DXRD, a number of untested
suggestions for methodological improvements and alternative applications are
included.
The book is written for a general reader who has a background in the
natural sciences and a basic understanding of x-ray diffraction. For historical
reasons, the majority of the applications presented relate to materials science.
However, as the structure of polycrystals is of more general interest it is my
hope that the book may serve to stimulate research in other fields also, such
as geophysics, geology, chemistry and pharmaceutical science.
Synchrotron instrumentation requires, by its nature, a collaborative effort.
Hence, I welcome this opportunity to thank the group of people who
have contributed towards the development of 3DXRD methodology. These
include Jacob Bowen, Xiaowei Fu, Stephan Garbe, Carsten Gundlach, Dorte
Juul Jensen, Erik Knudsen, Axel Larsen, Erik Mejdal Lauridsen, Torben
Lorentzen, Lawrence Margulies, Søren Fæster Nielsen, Wolfgang Pantleon,
Søren Schmidt, John Wert and Grethe Winther at Risø; Erik Offerman and
Jilt Sietsma at the Technical University of Delft; Robert Suter at CMU;
Rene Martins at GKSS; and, last but not least, Ulrich Lienert at the APS.
The development of the method into the 3DXRD microscope at ESRF was
only possible thanks to the dedication and expertise of the in-house staff,
in particular Andy Goetz, ˚Ake Kvick and Gavin Vaughan from beamline
ID11. The Danish National Research Foundation is gratefully acknowledged
for supporting “Center for Fundamental Research: Metal Structures in Four
Dimensions”.
The work presented in this book would not have been possible without
the pioneering studies in hard x-ray diffraction by Jochen Schneider. Furthermore,
for numerous very valuable discussions, I thank Roger Doherty, Niels
Hansen, Gabor Herman, Veijo Honkim¨aki, Torben Leffers, Wolfgang Ludwig,
Adam Morawiec and Jan Teuber.
Finally, I’m grateful to Roger Doherty, Dorte Juul Jensen and Brian Ralph
for reading and discussing this manuscript.
Roskilde, July 2004 Henning Friis Poulsen详细>