Carl-Georg Oertel

Formation and destruction of cube texture in MgO films using ion beam assisted pulsed laser deposition

Biaxially textured MgO thin films were deposited on amorphous substrates using ion beam assisted pulsed laser deposition. The development of the texture and microstructure was investigated with electron diffraction and atomic force microscopy. After the first few nanometers of growth, a sharp nucleation texture is observed. During further growth a texture change takes place, leading to two texture components, one in the 〈220〉 direction and the other in the 〈111〉 direction parallel to the substrate normal. In both cases the 〈200〉 direction is parallel to the ion beam. This texture change can be explained in terms of the highly anisotropic sputter rate observed in experiments on single crystals, leading to grains having a 〈200〉 direction parallel to the ion beam during growth being preferred. Without ion beam assistance during further growth, one of the two texture components dominates.

Microstructure and texture formation in extruded lead sulfide (galena)

Abstract Lead sulfide (galena) of different purity and grain size was extruded through a round and rectangular die at temperatures between 773 and 923 K. Global and local lattice preferred orientations (here referred to as textures) were measured by neutron and electron back-scattering diffraction. Tension leads to a double fibre texture. Pure shear deformation yields texture components near the ideal face-centered cubic metal brass, copper, Goss and cube positions. The intensity of the components depends on the purity and/or grain size. The microstructure is partially recrystallized. Electron back-scattering diffraction indicates that in tension the and in pure shear the Goss and cube components are associated with dynamic recrystallization. The deformation texture can be qualitatively explained by the full and relaxed constraints Taylor model using slip on {100} , {110} and {111} systems. The texture formation in lead sulfide compares well with that observed for other ionic crystals with the NaCl-structure as well as for face-centered cubic metals with a high stacking fault energy.

Mechanism of texture formation in MgO buffer layers using ion-beam assisted laser deposition

Abstract Biaxially textured MgO films have been grown using ion-beam assisted pulsed laser deposition. Above 250 °C a cube texture with a 〈1 1 0〉 direction parallel to the ion beam is observed in films thinner than 10 nm at ion incidence angles between 35° and 55°. The in-plane alignment determined using RHEED analysis was better than 21°. A strongly anisotropic sputter rate is responsible for this oriented nucleation. During further growth the nucleation texture changes in such a way that the 〈1 0 0〉 direction becomes parallel to the ion beam. This change can also be explained by the anisotropic sputter rate of MgO found in sputtering experiments on single crystals selecting grains with a 〈1 0 0〉 direction parallel to the ion beam during growth.

Grain refinement and texture formation in torsion deformed NiAl

Abstract Torsion at elevated temperatures and pressures was used to severely deform the intermetallic compound NiAl. The microstructure and texture as a function of shear strain were investigated by orientation imaging microscopy and diffraction of synchrotron radiation, respectively. The results show that at high shear strains a steady state grain structure and texture develops by continuous dynamic recrystallisation. The lowest grain size achieved is in the micron range, the main texture component is {110}<100>. It is concluded that high-strain torsion may open new possibilities in terms of grain refinement, texture formation and ductilisation of NiAl.

Microstructure Development During High Strain Torsion of NiAl

The microstructure development was investigated in torsion deformed NiAl. High strain torsion of solid bars was done with a Paterson rock deformation machine at temperatures between 700 K and 1300 K under a confining pressure of 400 MPa. The maximum shear strains and shear strain rates applied were 19 and 2.2 × 10 -4 s -1 , respectively. The shear stress-shear strain curves are characterized by a peak at low shear strains, which is followed by softening and a steady state at high shear strains. Increasing shear strain leads to grain refinement, with the average grain size decreasing with temperature. Moreover, a steady state grain aspect ratio and inclination of the grain long axis with respect to the shear plane is observed. With increasing shear strain, the fraction of low angle grain boundaries goes over a maximum and approaches a steady state of about 20-40%. The development of the microstructure is characterized by two different temperature regimes. Up to 1000 K, continuous dynamic recrystallization characterized by limited grain growth takes place, leading to a transformation of low into high angle grain boundaries. At temperatures above 1000 K, discontinuous dynamic recrystallisation occurs by massive grain growth. The results are qualitatively discussed on the basis of models dealing with dynamic recrystallization.

Texture Formation and Swift Effect in High Strain Torsion of NiAl

Texture formation and Swift effect were investigated in torsion deformed NiAl. High-strain torsion of solid bars was done with a Paterson rock deformation machine at temperatures between 700 K and 1300 K under a confining pressure of 400 MPa. The maximum shear strains and shear strain rates applied were 19×10 -4 s -1 and 2.2 ×10 -4 s -1 , respectively. Textures were measured by diffraction of neutrons, electrons, and synchrotron radiation. The textures consist of an oblique cube and Goss component, the intensity of which depends on the initial texture and deformation temperature. The axial lengthening and shortening observed are related to the Goss and the oblique cube components, respectively. There is qualitative agreement between experiment and simulation at low temperature and low shear strains. With increasing temperature, continuous and discontinuous dynamic recrystallization take place, strongly influencing the development of texture and Swift effect.

15th International Conference on the Strength of Materials (ICSMA-15)

The 15th International Conference on the Strength of Materials (ICSMA 15) took place in Dresden, Germany, August 16–21, 2009. It belongs to the triennial series of ICSMA meetings with a long tradition, starting in 1967 - Tokyo, 1970 - Asilomar, 1973 - Cambridge, 1976 - Nancy, 1979 - Aachen, 1982 - Melbourne, 1985 - Montreal, 1988 - Tampere, 1991 - Haifa, 1994 - Sendai, 1997 - Prague, 2000 - Asilomar, 2003 - Budapest, 2006 - Xian. ICSMA 15 was hosted by the Dresden University of Technology, Institute of Structural Physics. Following the tradition of this conference series, it was the main focus of ICSMA 15 to promote and strengthen the fundamental understanding of the basic processes that govern the strength of materials. Nonetheless, it was the aim to forge links between basic research on model materials and applied research on engineering materials of technical importance. Thus, ICSMA 15 provided a forum for the presentation and discussion of research on the mechanical properties of all materials which are of interest to materials scientists and engineers from many different areas. The topics covered by ICSMA 15 were: 1.Atomistic and microstructural aspects of plastic deformation 2.Atomistic and microstructural aspects of fracture 3.Adhesion and interfacial strength 4.Cyclic deformation and fatigue 5.High temperature deformation and creep 6.Mechanical properties related to phase transformations 7.Large and severe plastic deformation 8.Nano- and microscale phenomena in plasticity and fracture 9.Strength issues in biological systems and biomaterials 10.Mechanical behaviour of glasses and non-crystalline solids 11.Multiscale modelling and experimental validation 12.Insight through new experimental methods 13.Other new developments related to the field While there was large interest in the new topics 7 and 8, contributions to topic 9 were much less than expected. ICSMA 15 attracted 352 scientists from 30 countries with one fourth of the participants being students. This is a very good ratio showing that we could attract the young generation. There have been 272 oral and 135 poster presentations. It is our pleasure to thank the members of the International ICSMA Committee for their valuable help, especially for proposing and choosing the 18 plenary speakers. 187 papers were submitted for publication in the proceedings, 167 were accepted after reviewing. We would like to express our thanks to all referees for their efficient and prompt efforts. We acknowledge particularly support from the German Research Society (DFG), the Saxon Ministry for Science and Art and the City of Dresden. We are also grateful for industrial support from PLANSEE Metall GmbH, Goodfellow GmbH, MTS Systems GMB, Nagoya University and IOP Publishing. Finally we thank all members of the Local Organizing Committee, Intercom Dresden and Conwerk / Laboratory Ten for the excellent organization of ICSMA 15 and the very pleasant collaboration. During the conference the International ICSMA Committee decided to convene the next conference in Bangalore, India, in 2012. We wish the organizers of ICSMA 16 great success and look forward to meeting you in Bangalore. Werner Skrotzki (Technische Universitat Dresden) Carl-Georg Oertel (Technische Universitat Dresden) Horst Biermann (Bergakademie Technische Universitat Freiberg) Martin Heilmaier (Technische Universitat Darmstadt) Guest Editors Dresden, June 23, 2009 (* Corresponding author; e-mail address: werner.skrotzki@physik.tu-dresden.de)

Development of Texture and Microstructure in MgO Buffer Layers Using Ion-Beam Assisted Pulsed Laser Deposition

MgO thin films were deposited on amorphous substrates using ion-beam assisted pulsed laser deposition. The texture formation was investigated in-situ with RHEED. The microstructure of the films was observed by AFM. Using an ion beam at an angle between 35° and 65° with respect to the substrate normal, strong nucleation textures develop. Under certain deposition parameters a cube texture is observed in films thinner than 10nm. During further growth this nucleation texture changes in such a way that the «100» direction becomes parallel to the ion beam. This change can be explained by the anisotropic sputter rate of MgO seen in sputter experiments on single crystals. Moreover, MgO films were deposited homoepitaxially on MgO single crystals above 250° C with internal stresses decreasing with increasing deposition temperature. In contrast, films grown further on the thin cube-textured nucleation layer without ion-beam assistance show a texture change towards fibre textures.

17th International Conference on Textures of Materials (ICOTOM 17)

The 17th International Conference on Textures of Materials (ICOTOM 17) took place in Dresden, Germany, August 24-29, 2014. It belongs to the triennial series of ICOTOM meetings with a long tradition, starting in 1969 - Clausthal, 1971 - Cracow, 1973 - Pont-a-Mousson, 1975 - Cambridge, 1978 - Aachen, 1981 - Tokyo, 1984 - Noordwijkerhout, 1987 - Santa Fe, 1990 - Avignon, 1993 - Clausthal, 1996 - Xian, 1999 - Montreal, 2002 - Seoul, 2005 - Leuven, 2008 - Pittsburgh, 2011 - Mumbai, 2014 - Dresden. ICOTOM 17 was hosted by the Dresden University of Technology, Institute of Structural Physics. Following the tradition of the ICOTOM conferences, the main focus of ICOTOM-17 was to promote and strengthen the fundamental understanding of the basic processes that govern the formation of texture and its relation to the properties of polycrystalline materials. Nonetheless, it was the aim to forge links between basic research on model materials and applied research on engineering materials of technical importance. Thus, ICOTOM 17 provided a forum for the presentation and discussion of recent progress in research of texture and related anisotropy of mechanical and functional properties of all kinds of polycrystalline materials including natural materials like rocks. Particular attention was paid to recent advances in texture measurement and analysis as well as modeling of texture development for all kinds of processes like solidification, plastic deformation, recrystallization and grain growth, phase transformations, thin film deposition, etc. Hence, ICOTOM 17 was of great interest to materials scientists, engineers from many different areas and geoscientists. The topics covered by ICOTOM 17 were: 1. Mathematical, numerical and statistical methods of texture analysis 2. Deformation textures 3. Crystallization, recrystallization and growth textures 4. Transformation textures 5. Textures in functional materials 6. Textures in advanced materials 7. Textures in rocks 8. Texture related research on microstructures 9. Texture-induced anisotropy 10. Insight through new experimental methods 11. Technological applications of texture studies 12. Other new developments and future trends related to the field While there was large interest in the topics 2, 3 and 8, contributions to topic 7 were much less than expected. ICOTOM 17 attracted 266 scientists from 34 countries with about one third of the participants being students. This is a very good ratio showing that we could attract the young generation. There have been 216 oral and 76 poster presentations, three of which received a poster award. It is our pleasure to thank the members of the International ICOTOM Committee for their valuable help, especially for proposing and choosing the 15 plenary speakers as well as the distinguished scientist of the texture community for the Bunge Award. 130 papers were submitted for publication in the proceedings, 116 were accepted after reviewing. We would like to express our thanks to all referees for their efficient and prompt efforts. We acknowledge particularly support from the German Research Society (DFG) and the City of Dresden. We are also grateful for industrial support from Bruker Nano GmbH, Oxford Instruments GmbH, Ametek GmbH / EDAX, Labosoft S.C., PANalytical GmbH and IOP Publishing. Finally we thank all members of the National Organizing Committee, Intercom Dresden and Conwerk / Laboratory Ten for the excellent organization of ICOTOM 17 and the very pleasant collaboration. On the first day of the conference three tutorials have been offered. Each of them has been attended by about 30 participants. 1. Texture-aided residual stress identification system (TARSIuS) (organized by Prof. Dr. J. Bonarski and Mr. B. Kania) 2. MTEX - MATLAB toolbox for quantitative texture analysis (organized by Dr. R. Hielscher and Mr. F. Bachmann) 3. Grain boundary engineering (organized by Prof. N. Bozzolo and Prof. Dr. A.D. Rollett) A highlight of ICOTOM 17 was the ceremony honoring Prof. Dr. Claude Esling with the Bunge Award for his distinguished contributions to the field of Textures of Materials and his continuous effort to pass on his knowledge to future generations of texture experts. The Bunge Award is named after Professor Hans Bunge († 2004), to whom the worlds texture community is very much indebted not only for his magisterial work on the Mathematical Theory of Texture, but also for his lifelong promotion of the field of Textures of Materials. To the great delight of all participants, Helga Bunge and her son Prof. Hans-Peter Bunge, to whom many of the older generation have a personal relationship, attended the ceremony (see Fig. 1 in the PDF). Following the award ceremony Prof. Dr. Claude Esling gave an in memoriam tribute to Prof. Dr. Richard Penelle, who was an internationally recognized texture specialist. Details can be found in the proceedings paper by Esling et al. [this issue]. During the conference the International ICSMA Committee decided to convene the next conference in St. George, USA, in 2017. We wish the organizers of ICOTOM 18 great success and look forward to meeting you in St. George. Werner Skrotzki* (Chairman of ICOTOM 17, Dresden University of Technology) Carl-Georg Oertel (Dresden University of Technology) Guest Editors Dresden, March, 2015 (* Corresponding author; e-mail address: werner.skrotzki@tu-dresden.de)

Formation of Biaxially Textured MgO Buffer Layers using Ion-Beam Assisted Pulsed Laser Deposition

MgO thin films were deposited on amorphous substrates using ion-beam assisted pulsed laser deposition. The texture formation was investigated in-situ with RHEED. The microstructure of the films was observed by AFM. Using an ion beam at an angle of 55° with respect to the substrate normal, strong nucleation textures develop. Above 250°C a cube texture is observed in films thinner than 10 nm. During further growth this nucleation texture changes in a way that the direction becomes parallel to the ion beam. This change can be explained by the anisotropic sputter rate of MgO found in sputter experiments on single crystals. Moreover, MgO films were deposited homoepitaxially on MgO single crystals above 250°C with internal stresses dreasing with increasing deposition temperature. This result gives rise to hope that homoepitaxial growth of MgO on the nucleation layer without ion-beam assistance should be possible in future PLD-experiments keeping the desired cube texture in thicker films.