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	Author	Bartova, B.; Wiese, N.; Schryvers, D.; Chapman, J.N.; Ignacova, S.
	Title	Microstructure of precipitates and magnetic domain structure in an annealed Co₃₈Ni₃₃Al₂₉ shape memory alloy			Type	A1 Journal article
	Year	2008	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	56	Issue	16	Pages	4470-4476
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	The microstructure of a Co38Ni33Al29 ferromagnetic shape memory alloy was determined by conventional transmission electron microscopy (TEM), electron diffraction studies together with advanced microscopy techniques and in situ Lorentz microscopy. Rod-like precipitates, 1060 nm long, of hexagonal close-packed -Co were confirmed to be present by high-resolution TEM. The orientation relationship between the precipitates and B2 matrix is described by the Burgers orientation relationship. The crystal structure of the martensite obtained after cooling is tetragonal L10 with a (111) twinning plane. The magnetic domain structure was determined during an in situ cooling experiment using the Fresnel mode of Lorentz microscopy. While transformation proceeds from B2 austenite to L10 martensite, new domains are nucleated, leading to a decrease in domain width, with the magnetization lying predominantly along a single direction. It was possible to completely describe the relationship between magnetic domains and crystallographic directions in the austenite phase though complications existed for the martensite phase.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000259931300033	Publication Date	2008-06-11
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	23	Open Access
	Notes	Multimat			Approved	Most recent IF: 5.301; 2008 IF: 3.729
	Call Number	UA @ lucian @ c:irua:72321			Serial	2072
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	Author	Idrissi, H.; Renard, K.; Ryelandt, L.; Schryvers, D.; Jacques, P.J.
	Title	On the mechanism of twin formation in FeMnC TWIP steels			Type	A1 Journal article
	Year	2010	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	58	Issue	7	Pages	2464-2476
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Although it is well known that FeMnC TWIP steels exhibit high work-hardening rates, the elementary twinning mechanisms controlling the plastic deformation of these steels have still not been characterized. The aim of the present study is to analyse the extended defects related to the twinning occurrence using transmission electron microscopy. Based on these observations, the very early stage of twin nucleation can be attributed to the pole mechanism with deviation proposed by Cohen and Weertman or to the model of Miura, Takamura and Narita, while the twin growth is controlled by the pole mechanism proposed by Venables. High densities of sessile Frank dislocations are observed within the twins at the early stage of deformation, which can affect the growth and the stability of the twins, but also the strength of these twins and their interactions with the gliding dislocations present in the matrix. This experimental evidence is discussed and compared to recent results in order to relate the defects analysis to the macroscopic behaviour of this category of material.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000276523200018	Publication Date	2010-01-25
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	244	Open Access
	Notes	Iap			Approved	Most recent IF: 5.301; 2010 IF: 3.791
	Call Number	UA @ lucian @ c:irua:82270			Serial	2441
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	Author	Delville, R.; Malard, B.; Pilch, J.; Schryvers, D.
	Title	Microstructure changes during non-conventional heat treatment of thin NiTi wires by pulsed electric current studied by transmission electron microscopy			Type	A1 Journal article
	Year	2010	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	58	Issue	13	Pages	4503-4515
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Transmission electron microscopy, electrical resistivity measurements and mechanical testing were employed to investigate the evolution of microstructure and functional superelastic properties of 0.1 mm diameter as-drawn NiTi wires subjected to a non-conventional heat treatment by controlled electric pulse currents. This method enables a better control of the recovery and recrystallization processes taking place during the heat treatment and accordingly a better control on the final microstructure. Using a stepwise approach of millisecond pulse annealing, it is shown how the microstructure evolves from a severely deformed state with no functional properties to an optimal nanograined microstructure (2050 nm) that is partially recovered through polygonization and partially recrystallized and that has the best functional properties. Such a microstructure is highly resistant against dislocation slip upon cycling, while microstructures annealed for longer times and showing mostly recrystallized grains were prone to dislocation slip, particularly as the grain size exceeds 200 nm.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000279787100020	Publication Date	2010-06-02
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	110	Open Access
	Notes	Multimat; FWO IAA			Approved	Most recent IF: 5.301; 2010 IF: 3.791
	Call Number	UA @ lucian @ c:irua:83279			Serial	2062
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	Author	Cao, S.; Nishida, M.; Schryvers, D.
	Title	Quantitative three-dimensional analysis of Ni₄Ti₃ precipitate morphology and distribution in polycrystalline Ni-Ti			Type	A1 Journal article
	Year	2011	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	59	Issue	4	Pages	1780-1789
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	The three-dimensional size, morphology and distribution of Ni4Ti3 precipitates in a Ni50.8Ti49.2 polycrystalline shape memory alloy with a heterogeneous microstructure have been investigated using a focused ion beam/scanning electron microscopy slice-and-view procedure. The mean volume, central plane diameter, thickness, aspect ratio and sphericity of the precipitates in the grain interior as well as near to the grain boundary were measured and/or calculated. The morphology of the precipitates was quantified by determining the equivalent ellipsoids with the same moments of inertia and classified according to the Zingg scheme. Also, the pair distribution functions describing the three-dimensional distributions were obtained from the coordinates of the precipitate mass centres. Based on this new data it is suggested that the existence of the heterogeneous microstructure could be due to a very small concentration gradient in the grains of the homogenized material and that the resulting multistage martensitic transformation originates in strain effects related to the size of the precipitates and scale differences of the available B2 matrix in between the precipitates.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000287265100045	Publication Date	2010-12-20
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	34	Open Access
	Notes	Fwo			Approved	Most recent IF: 5.301; 2011 IF: 3.755
	Call Number	UA @ lucian @ c:irua:85533			Serial	2766
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	Author	Chen, X.; Cao, S.; Ikeda, T.; Srivastava, V.; Snyder, G.J.; Schryvers, D.; James, R.D.
	Title	A weak compatibility condition for precipitation with application to the microstructure of PbTe-Sb₂Te₃ thermoelectrics			Type	A1 Journal article
	Year	2011	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	59	Issue	15	Pages	6124-6132
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	We propose a weak condition of compatibility between phases applicable to cases exhibiting full or partial coherence and Widmanstätten microstructure. The condition is applied to the study of Sb2Te3 precipitates in a PbTe matrix in a thermoelectric alloy. The weak condition of compatibility predicts elongated precipitates lying on a cone determined by a transformation stretch tensor. Comparison of this cone with the long directions of precipitates determined by a slice-and-view method of scanning electron microscopy combined with focused ion beam sectioning shows good agreement between theory and experiment. A further study of the morphology of precipitates by the Eshelby method suggests that interfacial energy also plays a role and gives an approximate value of interfacial energy per unit area of 250 dyn cm−1.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000294086900026	Publication Date	2011-07-22
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	8	Open Access
	Notes				Approved	Most recent IF: 5.301; 2011 IF: 3.755
	Call Number	UA @ lucian @ c:irua:92388			Serial	3911
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	Author	Tirumalasetty, G.K.; van Huis, M.A.; Fang, C.M.; Xu, Q.; Tichelaar, F.D.; Hanlon, D.N.; Sietsma, J.; Zandbergen, H.W.
	Title	Characterization of NbC and (Nb, Ti)N nanoprecipitates in TRIP assisted multiphase steels			Type	A1 Journal article
	Year	2011	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	59	Issue	19	Pages	7406-7415
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Multiphase steels utilising composite strengthening may be further strengthened via grain refinement or precipitation by the addition of microalloying elements. In this study a Nb microalloyed steel comprising martensite, bainite and retained austenite has been studied. By means of transmission electron microscopy (TEM) we have investigated the size distribution and the structural properties of (Nb, Ti)N and NbC precipitates, their occurrence in the various steel phases, and their relationship with the Fe matrix. (Nb, Ti)N precipitates were found in ferrite, martensite, and bainite, while NbC precipitates were found only in ferrite. All NbC precipitates were found to be small (520 nm in size) and to have a face centred cubic (fcc) crystal structure with lattice parameter a = 4.36 ± 0.05 Å. In contrast, the (Nb, Ti)N precipitates were found to have a broader size range (5150 nm) and to have a fcc crystal structure with lattice parameter a = 8.09 ± 0.05 Å. While the NbC precipitates were found to be randomly oriented, the (Nb, Ti)N precipitates have a well-defined NishiyamaWasserman orientation relationship with the ferrite matrix. An analysis of the lattice mismatch suggests that the latter precipitates have a high potential for effective strengthening. Density functional theory calculations were performed for various stoichiometries of NbCx and NbxTiyNz phases and the comparison with experimental data indicates that both the carbides and nitrides are deficient in C and N content.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000296405200026	Publication Date	2011-09-29
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	58	Open Access
	Notes				Approved	Most recent IF: 5.301; 2011 IF: 3.755
	Call Number	UA @ lucian @ c:irua:93297			Serial	328
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	Author	Colla, M.-S.; Wang, B.; Idrissi, H.; Schryvers, D.; Raskin, J.-P.; Pardoen, T.
	Title	High strength-ductility of thin nanocrystalline palladium films with nanoscale twins : on-chip testing and grain aggregate model			Type	A1 Journal article
	Year	2012	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	60	Issue	4	Pages	1795-1806
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	The mechanical behaviour of thin nanocrystalline palladium films with an ∼30 nm in plane grain size has been characterized on chip under uniaxial tension. The films exhibit a large strain hardening capacity and a significant increase in the strength with decreasing thickness. Transmission electron microscopy has revealed the presence of a moderate density of growth nanotwins interacting with dislocations. A semi-analytical grain aggregate model is proposed to investigate the impact of different contributions to the flow behaviour, involving the effect of twins, of grain size and of the presence of a thin surface layer. This model provides guidelines to optimizing the strength/ductility ratio of the films.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000301989500035	Publication Date	2012-02-02
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	38	Open Access
	Notes	Iap			Approved	Most recent IF: 5.301; 2012 IF: 3.941
	Call Number	UA @ lucian @ c:irua:94213			Serial	1465
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	Author	Tirumalasetty, G.K.; van Huis, M.A.; Kwakernaak, C.; Sietsma, J.; Sloof, W.G.; Zandbergen, H.W.
	Title	Deformation-induced austenite grain rotation and transformation in TRIP-assisted steel			Type	A1 Journal article
	Year	2012	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	60	Issue	3	Pages	1311-1321
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	Uniaxial straining experiments were performed on a rolled and annealed Si-alloyed TRIP (transformation-induced plasticity) steel sheet in order to assess the role of its microstructure on the mechanical stability of austenite grains with respect to martensitic transformation. The transformation behavior of individual metastable austenite grains was studied both at the surface and inside the bulk of the material using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) by deforming the samples to different strain levels up to about 20%. A comparison of the XRD and EBSD results revealed that the retained austenite grains at the surface have a stronger tendency to transform than the austenite grains in the bulk of the material. The deformation-induced changes of individual austenite grains before and after straining were monitored with EBSD. Three different types of austenite grains can be distinguished that have different transformation behaviors: austenite grains at the grain boundaries between ferrite grains, twinned austenite grains, and embedded austenite grains that are completely surrounded by a single ferrite grain. It was found that twinned austenite grains and the austenite grains present at the grain boundaries between larger ferrite grains typically transform first, i.e. are less stable, in contrast to austenite grains that are completely embedded in a larger ferrite grain. In the latter case, straining leads to rotations of the harder austenite grain within the softer ferrite matrix before the austenite transforms into martensite. The analysis suggests that austenite grain rotation behavior is also a significant factor contributing to enhancement of the ductility. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000301157900054	Publication Date	2011-12-19
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	80	Open Access
	Notes				Approved	Most recent IF: 5.301; 2012 IF: 3.941
	Call Number	UA @ lucian @ c:irua:97210			Serial	630
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	Author	Malard, B.; Pilch, J.; Sittner, P.; Delville, R.; Curfs, C.
	Title	In situ investigation of the fast microstructure evolution during electropulse treatment of cold drawn NiTi wires			Type	A1 Journal article
	Year	2011	Publication	Acta materialia	Abbreviated Journal	Acta Mater
	Volume	59	Issue	4	Pages	1542-1556
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Microstructural changes taking place during the heat treatment of cold-worked NiTi alloy are of key interest in shape memory alloy technology, since they are responsible for setting the austenite shape and functional properties of the heat-treated alloy. In this work, microstructural evolution during non-conventional electropulse heat treatment of thin NiTi filaments was investigated in a unique high-speed in situ synchrotron X-ray diffraction experiment with simultaneous evaluation of the tensile force and electrical resistivity of the treated wire. The in situ results provide direct experimental evidence on the evolution of the internal stress and density of defects during fast heating from 20 °C to ∼700 °C. This evidence is used to characterize a sequence of dynamic recovery and recrystallization processes responsible for the microstructure and superelastic functional property changes during the electropulse treatments.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Oxford	Editor
	Language		Wos	000287265100023	Publication Date	2010-12-11
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1359-6454;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	5.301	Times cited	48	Open Access
	Notes				Approved	Most recent IF: 5.301; 2011 IF: 3.755
	Call Number	UA @ lucian @ c:irua:98372			Serial	1583
Permanent link to this record