Browsing NTNU Open by Author "Mathiesen, Ragnvald"
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2D in situ røntgenavbilding av aluminiumskum under kompresjon
Flatøe, Bjørnar Askeland (Master thesis, 2019)Dette studiet ble gjennomført for å bestemme nytteverdien av todimensjonale in situ røntgenavbildninger for å undersøke dynamiske prosesser i tredimensjonale prøver. Aluminium skumble undersøkt ved bruk av radiogram of ... -
Achieving dispersed fine soft Bi particles and grain refinement in a hypermonotectic Al-Bi alloy by severe plastic deformation and annealing
Zha, Min; Yu, Zhiyuan; Qian, Feng; Wang, Huiyuan; Li, Yanjun; Mathiesen, Ragnvald; Roven, Hans Jørgen (Journal article; Peer reviewed, 2018)The present work revealed that equal-channel angular pressing (ECAP) deformation combined with appropriate annealing could represent as an efficient route to modify immiscible as-cast microstructure of a monotectic Al–8Bi ... -
Analytical transmission cross-coefficients for pink beam X-ray microscopy based on compound refractive lenses
Falch, Ken Vidar; Detlefs, Carsten; Snigirev, Anatoly; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2018)Analytical expressions for the transmission cross-coefficients for x-ray microscopes based on compound refractive lenses are derived based on Gaussian approximations of the source shape and energy spectrum. The effects of ... -
Correcting lateral chromatic aberrations in non-monochromatic X-ray microscopy
Falch, Ken Vidar; Detlefs, Carsten; Di Michiel, Marco; Snigireva, Irina; Snigirev, Anatoly; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2016)Lateral chromatic aberration in microscopy based on refractive optics may be reduced significantly by adjustments to the illumination scheme. By taking advantage of a broadened bandwidth illumination, the proposed scheme ... -
Experimental and numerical modelling study on the nucleation and grain growth of inoculated aluminium alloys
Xu, Yijiang (Doctoral theses at NTNU;2017:343, Doctoral thesis, 2017)With the aim to achieve an in-depth understanding on the heterogeneous nucleation and grain growth behavior during solidification of inoculated aluminum alloys, an integrated study by in-situ X-radiography, numerical ... -
Experimental investigation of Gaussian random phase screen model for x-ray diffusers
Falch, Ken Vidar; Detlefs, Carsten; Christensen, Magnus Sebastian; Paganin, David; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2019)The beam diffusing properties of stacked layers of diffuser material were evaluated experimentally and compared to a Gaussian random phase screen model. The model was found to give promising accuracy in combination with a ... -
Faceted interfacial structure of {1011} twins in Ti formed during equal channel angular pressing
Li, Yanjun; Chen, Yongjun; Walmsley, John C.; Mathiesen, Ragnvald; Dumoulin, S; Roven, Hans Jørgen (Journal article; Peer reviewed, 2010)The boundary structure of {1011} deformation twins formed in commercial pure titanium (CP-Ti) during the initial pass ECAP processing has been studied by TEM and HRTEM. A new twining mode with twinning dislocation of b3/3, ... -
Heterogeneous nucleation and grain growth of inoculated aluminium alloys: An integrated study by in-situ X-radiography and numerical modelling
Xu, Yijiang; Casari, Daniele; Du, Qiang; Mathiesen, Ragnvald; Arnberg, Lars; Li, Yanjun (Journal article; Peer reviewed, 2017)A comprehensive study on the heterogeneous nucleation and grain growth of Al-10 wt.%Cu alloys inoculated with Al-5Ti-1B was carried out. To further reveal the solute segregation stifling mechanism, in-situ near-isothermal ... -
High-energy X-ray Transmission Microscopy based on Compound Refractive Lenses
Falch, Ken Vidar (Doctoral theses at NTNU;2017:124, Doctoral thesis, 2017)Summary of thesis: In the results of the work presented in this thesis it has been shown theoretically and demonstrated experimentally that lateral chromatic aberration in hard x-ray transmission microscopy can be ... -
In situ hard X-ray transmission microscopy for material science
Falch, Ken Vidar; Casari, Daniele; Di Michiel, Marco; Detlefs, Carsten; Snigirev, Anatoly; Snigireva, Irina; Honkimäki, Veijo; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2017)Hard X-ray transmission microscopy based on refractive X-ray optics can be employed as a tool in material science to investigate buried-in microstructures in two or three dimensions with spatial resolution approaching 100 ... -
In situ investigation of spinodal decomposition in hypermonotectic Al–Bi and Al–Bi–Zn alloys
Schaffer, Paul; Mathiesen, Ragnvald; Arnberg, Lars; Di Sabatino, Marisa; Snigirev, Anatoly (Journal article; Peer reviewed, 2008)Spinodal decomposition of hypermonotectic Al–6 wt.%Bi, Al–8 wt.%Bi and Al–6 wt.%Bi–8 wt.%Zn alloys has been investigated using synchrotron radiography. In the case of the 6 and 8 wt.%Bi binary alloys undercoolings of ... -
In-situ X-radiographic study of nucleation and growth behaviour of primary silicon particles during solidification of a hypereutectic Al-Si alloy
Xu, Yijiang; Deng, Yun; Casari, Daniele; Mathiesen, Ragnvald; Li, Yanjun (Peer reviewed; Journal article, 2020)Real-time observation of structure evolution in a hypereutectic Al-Si(-Cu) alloy under near-isothermal melt solidification condition was conducted by using in-situ micro-focus X-radiography. The nucleation, growth rate and ... -
Investigation of glitches induced by single-crystal diamond compound refractive lenses based on crystal orientation
Zhang, Qiuyuan; Polikarpov, Maxim; Nataliya, Klimova; Larsen, Helge Bøvik; Mathiesen, Ragnvald; Emerich, Hermann; Thorkildsen, Gunnar; Snigireva, Irina; Snigirev, Anatoly (Journal article; Peer reviewed, 2019)Single-crystal diamond is considered as an ideal material for compound refractive lenses (usually abbreviated to “CRLs”) mainly due to its stability when bathed in strong X-ray radiation. Since CRLs come into operation by ... -
Non-steady 3D dendrite tip growth under diffusive and weakly convective conditions.
Mirihanage, Wajira; Falch, Ken Vidar; Casari, Daniele; McFadden, Shaun; Browne, David J.; Snigireva, I.; Snigirev, Anatoly; Li, Yanjun; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2019)Three dimensional α-Al dendrite tip growth under varying solute gradients in an Al-Cu-Si alloy melt has been studied using real time synchrotron X-ray imaging and mathematical modelling. X-radiographic image sequences with ... -
Quantitative 3D Imaging and Metrology Using Coherent X-ray Scattering
Skjønsfjell, Eirik Torbjørn Bakken (Doctoral theses at NTNU;2017:300, Doctoral thesis, 2017)This thesis has focused on exploring methods of using coherent X-ray scattering at synchrotron sources. New imaging techniques using coherent X-ray scattering have been investigated, and it has been discussed how limitations ... -
Recrystallization and phase transformation of light metals induced by electric current flash heating
Wang, Shubo (Doctoral theses at NTNU;2020:186, Doctoral thesis, 2020)Aluminium (Al), and titanium (Ti) alloys are two commonly used light metal materials in the aerospace and automotive industry due to their high strength-to-weight ratio. Various heat treatments are applied to improve the ... -
Retrieval of three-dimensional spatial information from fast in situ two-dimensional synchrotron radiography of solidification microstructure evolution
Mirihanage, Wajira; Falch, Ken Vidar; Snigireva, Irina; Snigirev, A; Li, Yanjun; Arnberg, Lars; Mathiesen, Ragnvald (Journal article; Peer reviewed, 2014)In situ synchrotron X-ray radiography of columnar dendritic growth in Al–15 wt.% Cu–9 wt.% Si–0.015 wt.% Sr alloy has been carried out with the temporal and spatial resolutions of 100 ms and 0.65 μm, respectively. ... -
Revealing internal flow behaviour in arc welding and additive manufacturing of metals
Aucott, Lee; Dong, Hongbiao; Mirihanage, Wajira; Atwood, Robert; Kidess, Anton; Gao, Shian; Wen, Shuwen; Marsden, John; Feng, Shuo; Tong, Mingming; Connolley, Thomas; Drakopoulos, Michael; Kleijn, Chris R.; Richardson, Ian M.; Browne, David J.; Mathiesen, Ragnvald; Atkinson, Helen V. (Journal article; Peer reviewed, 2018)Internal flow behaviour during melt-pool-based metal manufacturing remains unclear and hinders progression to process optimisation. In this contribution, we present direct time-resolved imaging of melt pool flow dynamics ... -
Revealing the Heterogeneous Nucleation and Growth Behaviour of Grains in Inoculated Aluminium Alloys During Solidification
Xu, Yijiang; Casari, Daniele; Mathiesen, Ragnvald; Li, Yanjun (Peer reviewed; Journal article, 2019)An in situ X-ray radiographic study on the grain nucleation and grain growth of inoculated Al–10Cu and Al–20Cu alloys during isothermal melt solidification and directional solidification conditions with constant cooling ... -
Revealing the heterogeneous nucleation behavior of equiaxed grains of inoculated Al alloys during directional solidification
Xu, Yijiang; Casari, Daniele; Mathiesen, Ragnvald; Li, Yanjun (Journal article, 2018)An in-situ study on the directional solidification of an inoculated Al-20 wt%Cu alloy under well-controlled constant cooling rates and temperature gradients has been carried out using a microfocus X-radiography set-up. The ...