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Journal of Materials Science & Technology 2022年第7期102卷 89-96页

作者： Xu Liu Lin Song andreas stark Uwe Lorenz Zhanbing He Junpin Lin Florian Pyczak Tiebang Zhang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Institute of Materials Research Helmholtz-Zentrum GeesthachtMax Planck-Str.1Geesthacht 21502Germany State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

In modernβ-solidified TiAl alloys,the decomposition of α_(2) phase is frequently observed during heat treatment or high-temperature deformation of the alloys.In this study,high-temperature deformation and decomposition mechanisms of α_(2) phase in a Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y alloy are investigated.In a sample deformed at 800℃,the precipitation ofβ_(o)(ω_(o))phase is observed within the equiaxed α_(2) phase.The nucleation ofω_(o) particles within theβ_(o) matrix indicates the α_(2)→β_(o)→ω_(o) transformation.In addition,numerous y phase precipitates form within theβ_(o)(ω)areas.The α_(2) lamellae decompose into ultrafine( α_(2)+γ)lamellae and coarsened y lamellae via α_(2)→ α_(2)+γand α_(2)→γtransformation,re-spectively.Moreover,theω_(o) phase nucleates within the ultrafine lamellae via α_(2)→ω_(o) transformation.However,in a sample deformed at 1000℃,the nucleation ofβ_(o) particles is sluggish,which is caused by the efficient release of the internal stress via dynamic recrystallization(DRX).These results indicate that complex phase transformations can be introduced by the decomposition of α_(2) phase in TiAl alloys with a high amount ofβ-stabilizing elements.

关键词： TiAl alloys Phase transformation Microstructure Electron microscopy

On the reversibility of the α_(2)/ω_(o) phase transformation in a high Nb containing TiAl alloy during high temperature deformation

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Journal of Materials Science & Technology 2021年第34期93卷 96-102页

作者： Lin Song Fritz Appel andreas stark Uwe Lorenz Junyang He Zhanbing He Junpin Lin Tiebang Zhang Florian Pyczak State Key Laboratory of Solidification Processing Northwestern Poly technical University.Xi'an 710072China Institute of Materials Research Helmholtz-Zentrum GeesthachtMax Planck-Str.1Geesthacht 21502Germany Department of Microstructure Physics and Alloys Design Max-Planck-lnsdtut fiir Eisenforschung GmbHDusseldorf 40237Germany State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

The transformations between the phasesα_(2)(Ti_(3)Al)andω_(o)were investigated in a lamellar multiphase titanium aluminide alloy based onγ(TiAl).The paper complements an earlier investigation performed on the same material in which the importance of deformation-induced twin structures for theα_(2)→ω_(o) transformation was demonstrated.The present study shows that the reverse transformationω_(o)→α_(2) can also occur during high-temperature deformation.The transformation is probably triggered by constraint stresses,which exist between the different constituents due to the crystalline mismatch.The combined operation of mechanical twinning of theα_(2) phase and the reversible transformation fully converts theα_(2) lamellae into a mixture ofα_(2) andω_(o).This conversion greatly reduces the mechanical anisotropy existing in formerα_(2) lamellae.Regarding the technical use of the alloy,the stability of the converted structure with respect to further annealing was also examined.The reported processes occur at the nano-meter and sub nano-meter scale,thus,advanced characterization techniques were applied,such as high-resolution transmission electron microscopy(HRTEM)and atom probe tomography(APT).

关键词： TiAl alloys Phase transformation Electron microscopy Microstructure

Hot deformation of Mg-Y-Zn alloy with a low content of the LPSO phase studied by in-situ synchrotron radiation diffraction

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Journal of Magnesium and Alloys 2020年第1期8卷 199-209页

作者： Klaudia Horváth Fekete Daria Drozdenko Jan Capek Kristián Máthis Domonkos Tolnai andreas stark Gerardo Garcés Patrik Dobron Department of Physics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116 PragueCzech Republic Nuclear Physics Institute of the CAS 25068ˇRežCzech Republic Magnesium Research Center Kumamoto University2-39-1 Kurokami Chuo-ku860-8555 KumamotoJapan Laboratory for Neutron Scattering and Imaging Paul Scherrer InstituteVilligen PSI5232Switzerland Institute of Materials Science Helmholtz-Zentrum GeesthachtMax-Planck Str.1GeesthachtD21502Germany Department of Physical Metallurgy CENIM-CSICAvenida Gregorio del Amo 8E-28040 MadridSpain

The compressive deformation behavior of the extruded WZ42(Mg98.5Y1Zn0.5 in at.%)magnesium alloy containing a low amount of long-period stacking ordered(LPSO)phase was studied by in-situ synchrotron radiation diffraction technique.Tests were conducted at temperatures between room temperature and 350℃.Detailed microstructure investigation was provided by scanning electron microscopy,particularly the backscattered electron imaging and electron backscatter diffraction technique.The results show that twinning lost its dominance and kinking of the LPSO phase became more pronounced with increasing deformation temperature.No cracks of the LPSO phase and no debonding r at the interface between the LPSO phase and the Mg matrix were observed at temperatures above 200℃.At 350℃,the LPSO phase lost its strengthening effect and the deformation of the alloy was mainly realized by the dynamic recrystallization of the Mg matrix.

关键词： Magnesium alloy LPSO phase Kinking High temperature Synchrotron radiation diffraction

Miniaturization of a coherent monocular structured illumination system for future combination with digital holography

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Light(Advanced Manufacturing) 2022年第3期3卷 160-167页

作者： andreas Walter stark Eugene Wong Holger Babovsky Christian Franke Richard Kowarschik Institute of Applied Optics and Biophysics Friedrich Schiller University Jena07743 JenaGermany University Hospital 07743 JenaGermany

Holographic and 3D-measurement processes are an often-used tool in industry,medicine,and scientific applications.While small deviations of objects can be visualized by holographic means with high accuracy,optical systems with active structured illumination are a reliable source of absolute 3D-information in these fields.The combination of digital holography with structured illumination allows to simultaneously measure deformations and absolute 3D coordinates but also requires coherent light and has already been demonstrated in principle with a stereo camera setup.Multi-camera systems are limited to certain setup sizes given by the volume and distance of the detectors.Reducing the system to a one-camera(monocular)setup reduces space and acquisition costs.By using a multi-aperture illumination source an extremely high projection rate could be realized and reduced to a monocular approach with a novel voxel-calibration technique,while the projection system itself still requires a large amount of space.In this paper we present a miniaturized,monocular 3D-measurement system that works with repeatable,coherent speckles,generated by a fiber-coupled laser whose light was distributed by a fiber-switch to a diffuser plate connected with a measurement-head,also including a camera.By addressing different fibers through the switch,varying but repeatable patterns are generated.The size of the device(diameter<3 cm)is now mainly limited by the volume of the camera.A first 3D-reconstruction of an object and an outlook for a combination of this system with digital holography is given,allowing absolute 3D-coordinates and relative deviations of object points to be measured simultaneously.

关键词： 3D-measurement Structured illumination Speckle projection Monocular 3D-measurement Combination 3D-measurment and holography

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汽车制造商竞争2020

中国企业家 2002年第2期38卷 122-123页

作者： andreas Maurer Wilko andreas stark 波士顿咨询公司杜塞尔多夫办公室副总裁斯图加特办公室顾问

到2020年,这个“熟悉的产业”

关键词：汽车制造商汽车工业市场竞争发展趋势世界材料车型 2020年