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1

Metal Structures in Four Dimensions

Schmidt S., Jensen D. J.

Archives of Metallurgy and Materials

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2005

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Vol. 50, iss. 1

181-187

EN

The Three Dimensional X-ray Diraction (3DXRD) microscope located at the European Synchrotron Radiation Facility (ESRF) in Grenoble, developed in collaboration between Risoe and the ESRF, utilizes high energy x-rays to investigate processes such as plastic deformation, phase transformation, recovery and recrystallization non-destructively in the bulk of materials. Lately, an annealing experiment using a deformed aluminum single crystal has shown that it is possible to follow in-situ the evolution of the three dimensional shape of a single grain as function of annealing time, i.e. a four dimensional measurement of a recrystallizing grain. Contradictory to classical models, where the growth is assumed to be spherical and smooth, the measured grain exhibits a very irregular shape along with abrupt movements of the individual boundary segments. The experimental method also makes it possible to monitor the texture components of the deformed microstructure as it shrink in size due to growth of the recrystallized volume. The talk will give an overview of the experimental method and discuss its potential. In addition, a number of examples from the analysis will be presented.

PL

Trójwymiarowa mikroskopia dyfrakcji rentgenowskiej (3DXRD) zlokalizowana w European Synchrotron Radiation Facility (ESRF) w Grenoble, rozwinieta we współpracy pomiędzy Risoe i ESRF wykorzystuje wysokoenergetyczna wiązkę rentgenowską do nieniszczących badań takich procesów jak deformacja plastyczna, przemiana fazowa, zdrowienie i rekrystalizacja w objętości materiału. Ostatnio, możliwa jest obserwacja in-situ rozwoju rekrystalizacji 3-wymiarowego kształtu pojedynczego ziarna odkształconego monokryształu aluminium w funkcji czasu wygrzewania, tj. czwartego wymiaru. W odróżnieniu do modeli klasycznych, w których zakłada się regularny i sferyczny wzrost, mierzone ziarno wykazuje bardzo nieregularny kształt z gwałtownymi przemieszczeniami segmentów granicy pojedynczych ziaren. Wprowadzona metoda eksperymentalna umożliwia również monitorowanie składowych tekstury odkształconej mikrostruktury kurczącej się podczas wzrostu objętości zrekrystalizowanej. W pracy omówiono metodę i przedyskutowano jej możliwości, podając wiele przykładów zastosowania.

2

Nanostructured metals - processing, microstructure and properties.

Hansen N., Jensen D.J.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

1006-1011

EN

Nanostructured metals and alloys processed by plastic deformation are described with emphasis on their structural evolution and on correlations between structure and mechanical properties. Various processes are considered both conventional ones (e.g. rolling, drawing and torsion) and new ones (e.g. accumulative roll bonding, cyclic extrusion compression and equal channel angular extrusion). For all these processes it is a general finding that the structure evolves by subdivision of grains by deformation induced boundaries forming a cell block structure, which refines with increasing strain. A number of structural parameters are defined and analysed leading to qualitative and quantitative correlations between processing parameters and structure and between structural parameters and mechanical properties.

3

Modern modelling of recrystallization.

Jensen D.J.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

637-644

EN

A new trend in recrystallization modelling is to analyse microstructural and textural changes simultaneously by including orientation aspects of nucleation and of growth in the models. Compared to traditional recrystallization models, which focus on either microstructure or texture, the new models are more realistic and lead to much more precise predictions of specific recrystallization experiments. In the present paper, the various approaches of this modern recrystallization modelling is described and discussed.

4

Microtexture and microstructure investigations by orientation imaging microscopy.

Bunsch A., Jensen D.J., Hansen N.

Inżynieria Materiałowa

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1998

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R. XIX, nr 3

455-458

EN

The OIM technique is presented and examples of OIMs from recrystallized and cold deformed aluminium are given. It was found that the grain structures of the recrystallized samples are well resolved by the OIMs. Grain subdivision on different length scales during deformation is also clearly visible. The development in orientational grain subdivision is followed as a function of strain up to Epsilon=0.8 and the results are presented both by OIM pictures, average misorientations and misorientation distributions. Finally the potentials of the OIM technique are discussed.

5

Formation of fine grains in aluminium deformed to large strains.

Richert M., Hansen N., Richert J., Jensen D.J., Liu Q., Godfrey A.

Inżynieria Materiałowa

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1998

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R. XIX, nr 3

502-505

EN

Pure aluminium (99,992%) deformed to large strains by CEC method has been annealed in the temperature range from 373 to 563 K. After annealing at 513 K a partly recrystallized microstructure with small grains is observed. An analysis of the changes in microstructure suggests that both discontinuous and continuous recrystallization might have taken place.