Kirchheim, Reiner

[["dc.bibliographiccitation.firstpage","347"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Microscopy and Microanalysis"],["dc.bibliographiccitation.lastpage","353"],["dc.bibliographiccitation.volume","13"],["dc.contributor.author","Choi, Pyuck-Pa"],["dc.contributor.author","Al-Kassab, Tala'at"],["dc.contributor.author","Kwon, Young-Soon"],["dc.contributor.author","Kim, Ji-Soon"],["dc.contributor.author","Kirchheim, Reiner"],["dc.date.accessioned","2018-11-07T10:58:16Z"],["dc.date.available","2018-11-07T10:58:16Z"],["dc.date.issued","2007"],["dc.description.abstract","Focused ion-beam milling has been applied to prepare needle-shaped atom probe tomography specimens from mechanically alloyed powders without the use of embedding media. The lift-out technique known from transmission electron microscopy specimen preparation was modified to cut micron-sized square cross-sectional blanks out of single powder particles. A sequence of rectangular cuts and annular milling showed the highest efficiency for sharpening the blanks to tips. First atom probe results on a Fe(95)Cu(5) powder mechanically alloyed in a high-energy planetary ball mill for 20 h have been obtained. Concentration profiles taken from this powder sample showed that the Cu distribution is inhomogeneous on a nanoscale and that the mechanical alloying process has not been completed yet. In addition, small clusters of oxygen, stemming from the ball milling process, have been detected. Annular milling with 30 keV Ga ions and beam currents >= 50 pA was found to cause the formation of an amorphous surface layer, whereas no structural changes could be observed for beam currents <= 10 pA."],["dc.identifier.doi","10.1017/S1431927607070717"],["dc.identifier.isi","000250127700006"],["dc.identifier.pmid","17900385"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/50440"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Cambridge Univ Press"],["dc.relation.issn","1431-9276"],["dc.title","Application of focused ion beam to atom probe tomography specimen preparation from mechanically alloyed powders"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","240"],["dc.bibliographiccitation.issue","2-3"],["dc.bibliographiccitation.journal","Surface and Interface Analysis"],["dc.bibliographiccitation.lastpage","245"],["dc.bibliographiccitation.volume","39"],["dc.contributor.author","Heinrich, Andreas J."],["dc.contributor.author","Al-Kassab, Tala'at"],["dc.contributor.author","Kirchheim, Reiner"],["dc.date.accessioned","2018-11-07T11:05:36Z"],["dc.date.available","2018-11-07T11:05:36Z"],["dc.date.issued","2007"],["dc.description.abstract","The initial stages of nucleation and precipitation of the Co-rich phase in a supersaturated Cu2at.%Co alloy were studied with the field ion microscope (FIM) and the tomographic atom probe (TAP). The specimens of nominal composition Cu2at.%Co were homogenised at 1173 K and aged for different times at different temperatures from 703 to 833 K to follow the decomposition path at these reaction temperatures. In this paper, results on the time evolution of the decomposition are presented. New aspects in the decomposition of CuCo were found, which are discussed. At the initial stages of the nucleation, fluctuations were observed, which could be quantitatively characterised. Decomposition was found to take different paths at different annealing temperatures. At 853 K individual precipitates grew, whereas during coarsening the elastic soft [100] directions were preferred. At 763 K, cigar-shaped precipitates formed along the [100] directions as a metastable state, which degraded into individual spherical precipitates for longer aging times. The initial stages of decomposition were also characterised for 703 K by using the cluster search algorithm. Copyright (C) 2007 John Wiley & Sons, Ltd."],["dc.identifier.doi","10.1002/sia.2522"],["dc.identifier.isi","000244295600031"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/52108"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","John Wiley & Sons Ltd"],["dc.publisher.place","Chichester"],["dc.relation.conference","49th International Field Emission Symposium"],["dc.relation.eventend","2004-07-15"],["dc.relation.eventlocation","Graz, Austria"],["dc.relation.eventstart","2004-07-12"],["dc.relation.issn","0142-2421"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Investigation of new aspects in the initial stages of decomposition of Cu2at.%Co with the tomographic atom probe and the field ion microscope"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","730"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Ultramicroscopy"],["dc.bibliographiccitation.lastpage","737"],["dc.bibliographiccitation.volume","111"],["dc.contributor.author","Wille, Catharina G."],["dc.contributor.author","Al-Kassab, Tala'at"],["dc.contributor.author","Kirchheim, Reiner"],["dc.date.accessioned","2018-11-07T08:56:16Z"],["dc.date.available","2018-11-07T08:56:16Z"],["dc.date.issued","2011"],["dc.description.abstract","Being widely accessible as well as already utilised in many applications, Fe-Cu acts as an ideal binary model alloy to elaborate the enforced nonequilibrium enhanced solubility in such a solution system that shows a limited regime of miscibility and characterised by a large positive heat of mixing. In addition to the detailed analysis of ball milled Fe-Cu powders by means of Atom Probe Tomography (APT), site specific structural analysis has been performed in this study using Transmission Electron Microscopy (TEM). In this contribution results on powders with low Cu concentrations (2.5-10 at%) are presented. Combining a ductile element (Cu, fcc) and a brittle one (Fe, bcc), striking differences in morphology were expected and found on all length-scales, depending on the mixing ratio of the two elements. However, not only could the atomic mixing of Fe and Cu be evaluated, but also the distribution of impurities, mostly stemming from the fabrication procedure. The combination of APT and TEM enables a correlation between the structural evolution and the chemical mixing during the milling process. For the first time, a clear distinction can be drawn between the morphological evolution at the surface and in the interior of the powder particles. This became possible owing to the site specific sample preparation of TEM lamellae by Focussed Ion Beam (FIB). Surprisingly, the texture arising from the ball milling process can directly be related to the classical rolling texture of cold rolled Fe. In addition, full homogeneity can be achieved even on the nano-scale for this material as shown by APT, resulting in an extended miscibility region in comparison to the equilibrium phase diagram. Grain sizes were determined by means of XRD and TEM. The strain corrected XRD results are in very good agreement with the values derived by TEM, both confirming a truly nanocrystalline structure. (C) 2011 Elsevier B.V. All rights reserved."],["dc.description.sponsorship","Deutsche Forschungsgemeinschaft [KI-230/33-1]"],["dc.identifier.doi","10.1016/j.ultramic.2011.01.036"],["dc.identifier.isi","000300460900065"],["dc.identifier.pmid","21664545"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/23101"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.publisher.place","Amsterdam"],["dc.relation.conference","52nd International Field Emission Symposium"],["dc.relation.eventend","2010-07-08"],["dc.relation.eventlocation","Sydney, AUSTRALIA"],["dc.relation.eventstart","2010-07-05"],["dc.relation.issn","1879-2723"],["dc.relation.issn","0304-3991"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Time evolution of morphology in mechanically alloyed Fe-Cu"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2136"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science"],["dc.bibliographiccitation.lastpage","2143"],["dc.bibliographiccitation.volume","42A"],["dc.contributor.author","Semboshi, Satoshi"],["dc.contributor.author","Nishida, Tomoya"],["dc.contributor.author","Numakura, Hiroshi"],["dc.contributor.author","Al-Kassab, Tala'at"],["dc.contributor.author","Kirchheim, Reiner"],["dc.date.accessioned","2018-11-07T08:54:09Z"],["dc.date.available","2018-11-07T08:54:09Z"],["dc.date.issued","2011"],["dc.description.abstract","To improve the balance of the electrical conductivity and mechanical strength for dilute Cu-Ti alloys by aging in a hydrogen atmosphere, the influence of aging temperature ranging from 673 K to 773 K (400 A degrees C to 500 A degrees C) on the properties of Cu-3 at. pct Ti alloy was studied. The Vickers hardness increases steadily with aging time and starts to fall at 3 hours at 773 K (500 A degrees C), 10 hours at 723 K (450 A degrees C), or over 620 hours at 673 K (400 A degrees C), which is the same as the case of conventional aging in vacuum. The maximum hardness increases from 220 to 236 with the decrease of aging temperature, which is slightly lower than aging at the same temperature in vacuum. The electrical conductivity at the maximum hardness also increases from 18 to 32 pct of pure copper with the decrease of the temperature, which is enhanced by a factor of 1.3 to 1.5 in comparison to aging in vacuum. Thus, aging at 673 K (400 A degrees C) in a hydrogen atmosphere renders fairly good balance of strength and conductivity, although it takes nearly a month to achieve. The microstructural changes during aging were examined by transmission electron microscopy (TEM) and atom-probe tomography (APT), and it was confirmed that precipitation of the Cu(4)Ti phase occurs first and then particles of TiH(2) form as the third phase, thereby efficiently removing the Ti solutes in the matrix."],["dc.identifier.doi","10.1007/s11661-011-0637-8"],["dc.identifier.isi","000291704200002"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/7377"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22605"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","1073-5623"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","Goescholar"],["dc.rights.uri","https://goedoc.uni-goettingen.de/licenses"],["dc.title","Effects of Aging Temperature on Electrical Conductivity and Hardness of Cu-3 at. pct Ti Alloy Aged in a Hydrogen Atmosphere"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","246"],["dc.bibliographiccitation.issue","2-3"],["dc.bibliographiccitation.journal","Surface and Interface Analysis"],["dc.bibliographiccitation.lastpage","250"],["dc.bibliographiccitation.volume","39"],["dc.contributor.author","Wolde-Giorgis, Daniel"],["dc.contributor.author","Al-Kassab, Tala'at"],["dc.contributor.author","Kirchheim, Reiner"],["dc.date.accessioned","2022-01-27T09:48:34Z"],["dc.date.available","2022-01-27T09:48:34Z"],["dc.date.issued","2007"],["dc.identifier.doi","10.1002/sia.2523"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/98692"],["dc.relation.issn","0142-2421"],["dc.relation.issn","1096-9918"],["dc.relation.orgunit","Institut für Materialphysik"],["dc.title","Grain-boundary segregation in nanocrystalline CuBi layers studied with the tomographic atom probe"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]