Miha Založnik

Miha Založnik
French National Centre for Scientific Research | CNRS · Institut Jean Lamour, Nancy

PhD

About

129
Publications
27,225
Reads
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1,764
Citations
Additional affiliations
September 2001 - October 2006
Impol d.d.
Position
  • Researcher
November 2009 - present
French National Centre for Scientific Research
Position
  • Instabilities of Heat and Mass Transfer in a Solidifying Mushy Zone
November 2006 - October 2009
University of Lorraine
Position
  • Modeling of Macrosegregation and Microstructure in Steel and Aluminium Casting
Education
November 2001 - October 2006
University of Nova Gorica
Field of study
  • Materials Characterization - Modeling of Materials and Processes
October 1995 - September 2001
University of Ljubljana
Field of study
  • Mechanical Engineering

Publications

Publications (129)
Article
Full-text available
Grain growth during the solidification of an alloy is accompanied by the enrichment of the surrounding liquid phase in chemical species. The resulting diffusion fields induce interactions between the grains that are strongly dependent on their spatial arrangement. The influence of these diffusive interactions is not limited to the shapes and sizes...
Article
Full-text available
To provide quantitative predictions, multiscale models of dendritic solidification (e.g., GEM, DNN, CAFE) need to be validated and require model parameters, which can be calculated by phase-field simulations. We report on a multiscale modeling of dendritic solidification in samples that are cooled homogeneously at a constant rate. We consider three...
Article
Full-text available
Mesosegregation appears during the solidification of low-alloyed steels at the scale of a few grains. It causes chemically segregated bands in forgings manufactured from steel ingots. As this may affect the mechanical properties of the produced parts, it is crucial to understand the formation of such segregation patterns. While both microsegregatio...
Article
Full-text available
Ti-Al alloys have replaced Ni-based superalloys in the last stages of some aircraft engines to improve fuel efficiency. In order to improve their properties, grain refinement has been investigated via isomorphic inoculation with Ti-Al-Nb particles. This inoculation method is orders of magnitude more efficient on a particle-by-particle basis than tr...
Article
Full-text available
The chemical composition mapping of low-alloyed steel ingots used for the nuclear industry is crucial in the manufacturing of forgings and their final quality mastering. Mechanical properties of forged and hot-rolled steels may be affected by chemically segregated bands. These bands arise from segregations that appear at the scale of a few grains i...
Article
Full-text available
The ICASP conference series is a preeminent forum for researchers to discuss the latest advances and future directions in solidification science . The 6th edition was held 20-24 June 2022 at “Le Bischenberg”, in Bischoffsheim, on the Alsace Wine Route and at the foot of the Vosges in the east of France. ICASP-6 covered all aspects of research and a...
Article
Full-text available
The grain envelope model (GEM) describes the growth of envelopes of dendritic crystal grains during solidification. Numerically the growing envelopes are usually tracked using an interface capturing method employing a phase field equation on a fixed grid. Such an approach describes the envelope as a diffuse interface, which can lead to numerical ar...
Article
The chemical homogeneity and metallurgical structure of vacuum arc remelted (VAR) zirconium ingots are directly responsible for product quality. It is therefore important to understand the relationship between these properties and the operating conditions. An in-depth analysis of the modelling of solidification phenomena during the VAR was carried...
Preprint
Full-text available
The grain envelope model (GEM) describes the growth of envelopes of dendritic crystal grains during solidification. Numerically the growing envelopes are usually tracked using an interface capturing method employing a phase field equation on a fixed grid. Such an approach describes the envelope as a diffuse interface, which can lead to numerical ar...
Article
A model of mushy zone instability is developed for characterization and prediction of channel segregation in castings. The model highlights the connection of the mushy zone instability with the mush permeability. A new criterion for amplification of the mush instability is derived, which depends on the interdendritic velocity, the isotherm velocity...
Article
Full-text available
A series of single-track selective laser melting (SLM) experiments was carried out on IN718 plates with and without a powder layer and with different laser processing parameters (power and scan velocity) and surface conditions (original surface and sand blasted surface). The impacts of the powder, laser parameters, and surface conditions on the mol...
Article
Quantitative modeling of solidification microstructures growing under the influence of convection is a challenging multiscale problem. It is of particular interest in processes where strong flow is present, such as centrifugal casting of Ti–Al alloys, where hypergravity strongly reinforces the buoyancy-driven flow. We present the coupling of the me...
Article
Full-text available
We present a quantitative benchmark of multiscale models for dendritic growth simulations. We focus on approaches based on phase-field, dendritic needle network, and grain envelope dynamics. As a first step, we focus on isothermal growth of an equiaxed grain in a supersaturated liquid in three dimensions. A quantitative phase-field formulation for...
Article
Full-text available
Macrosegregation is a severe defect present in direct-chill (DC) cast aluminium ingots and billets. In the recent years, experimental studies were conducted to modify and to an extent optimize macrosegregation formation by modifying the inlet melt flow. Due to several limitations, the grain settling behavior and corresponding liquid flow pattern is...
Article
Full-text available
The control of the carbon macrosegregation level in steel ingots is important for the structural integrity of the final component. Previous studies using the SOLID® multiscale modelling software have shown that in order to obtain predictive results for the macrosegregation and the grain structure (CET, grain morphology) in steel ingots, a model nee...
Article
Experiments of directional solidification of TiAl cylindrical samples were conducted within the frame of the ESA GRADECET project. The experiments were performed in the ESA “Large Diameter Centrifuge” using a furnace with a well defined thermal protocol. The furnace was mounted in the centrifuge and free to tilt in such a way that the total apparen...
Preprint
We present a quantitative benchmark of multiscale models for dendritic growth simulations. We focus on approaches based on phase-field, dendritic needle network, and grain envelope dynamics. As a first step, we focus on isothermal growth of an equiaxed grain in a supersaturated liquid in three dimensions. A quantitative phase-field formulation for...
Article
A 3D meso-scale model is developed to predict the flow of liquid within a semi-solid binary Fe-C alloy with various equiaxed microstructure, ranging from dendritic to globular. The model domain consists of a set of 8000 grains given by a Voronoi tessellation. Solidification of each grain is simulated independently via a volume average approach, pro...
Article
The main objective of the present paper is to define a new benchmark test for macrosegregation in axisymmetry and to verify a novel meshless method on it. The test case represents a solidification of Al4.5 wt%Cu alloy in two different types of geometries, a solid and a hollow cylinder, cooled at the vertical boundaries. The volume averaging method...
Article
Full-text available
Within the framework of the ESA GRADECET project, experiments of directional solidification of cylindrical Ti-Al samples were conducted in hypergravity. The experiments were performed in a centrifuge with the apparent gravity (sum of centrifugal and terrestrial gravity) aligned along the cylinder centerline. 3D numerical simulations of aluminum mac...
Article
Full-text available
Correct prediction of composition heterogeneities and grain structure across a steel ingot is critical in optimizing the industrial processing parameters for enhanced performance. The columnar to equiaxed transtion (CET) is a microstructural transition which is strictly controlled as it affects the mechanical properties of the final product along w...
Article
Full-text available
A 3D mesoscopic envelope model is used to numerically simulate the experimental X-ray observations of the equiaxed dendritic isothermal solidification of a thin sample of Al-20 wt%Cu alloy including the natural convection flow. Several four-grain simulations are run to investigate the effect of the convection, of the grain position, and of the grai...
Article
Full-text available
The control of the carbon macrosegregation level in steel ingots is important for the structural integrity of the final component. During solidification, the fragmentation of the columnar dendrites is an important source of equiaxed grains, and has a large influence on the macrosegregation and the grain structure. The goal of this study is to show...
Article
Full-text available
A 3D meso-scale discrete-element model has been developed to simulate fluid flow during dendritic solidification of steel. The model domain is a representative volume element consisting of a set of equiaxed dendritic grain envelopes along with extra-dendritic liquid channels, where the final grain shape is given by a Voronoi tessellation. Solidific...
Article
A 3D mesoscopic envelope model is used to numerically simulate the experimental X-ray observations of isothermal equiaxed dendritic solidification of a thin sample of Al-20 wt % Cu alloy. We show the evolution of the system composed of multiple grains growing under influence of strong solutal interactions. We emphasize the three-dimensional effects...
Article
Full-text available
A simplified three-phase, multiscale macrosegregation model which describes the growth kinetics of equiaxed grains and the coupling between microstructure morphology and the macroscopic transport has been proposed previously. In this paper, the model is validated by comparing the numerical model predictions to the experimental data from DC casting...
Article
Full-text available
This paper addresses the phenomenon of random packing of sedimenting grains in the context of metallic alloy solidification from a dynamics perspective. More precisely, we investigate the evolution of the grains from the initial steady-state sedimentation until the final mechanical equilibrium—packing—is achieved. The packing dynamics of two grain...
Article
Full-text available
Macroscale solidification models incorporate the microscale and mesoscale phenomena of dendritic grain growth using constitutive relations. These relations can be obtained by simulating those phenomena inside a Representative Elementary Volume (REV) and then upscaling the results to the macroscale. In the present study, a previously developed mesos...
Conference Paper
Full-text available
Nonuniform solute distribution at the scale of the cast product is referred to as macrosegregation. This is a common defect observed in direct chill (DC) casting of aluminium alloys. Transport mechanisms such as solidification shrinkage induced flow, thermal-solutal convection and equiaxed grain motion contribute to this defect. Casting parameters,...
Article
Full-text available
Direct chill (DC) casting of aluminum involves alloys employing different solute elements. In this article, a qualitative analysis and comparison of macrosegregation formation is presented for three different alloy systems: Al-Mg, Al-Zn and Al-Cu. For this purpose, a multiphase, multiscale solidification model based on a volume-averaging method acc...
Article
Full-text available
Macrosegregation is a result of the interplay of various transport mechanisms, including natural convection, solidification shrinkage, and grain motion. Experimental observations also indicate the impact of grain morphology, ranging from dendritic to globular, on macrosegregation formation. To avoid the complexity arising due to modelling of an equ...
Poster
Full-text available
Direct Chill (DC) Casting of Aluminium involves alloys employing different solute elements. Shrinkage induced flow, thermal-solutal convection and grain motion are some of the transport mechanisms resulting in inhomogeneity of these solute elements which is referred to as macrosegregation. In the current research, a qualitative analysis and compari...
Article
Full-text available
The transport of solid crystals in the liquid pool during solidification of large ingots is known to have a significant effect on their final grain structure and macrosegregation. Numerical modeling of the associated physics is challenging since complex and strong interactions between heat and mass transfer at the microscopic and macroscopic scales...
Chapter
Full-text available
Several transport mechanisms contribute to macrosegregation formation in Direct Chill (DC) casting of aluminium. The latter include solidification shrinkage induced flow, thermal-solutal convection and grain motion. The relative importance of these transport mechanisms depends on process parameters such as cast velocity, inlet melt flow, cooling ra...
Article
Full-text available
The packing of free-floating crystal grains during solidification has a strong impact on the phase-change process as well as on the structure and the defects in the solidified material. The packing fraction is affected by the particular dendritic morphology of the grains and by their low inertia resulting from the small density difference between s...
Article
Full-text available
A volume average model to study the transition of a semi-solid mushy zone to a planar solid/liquid interface in a static temperature gradient is presented. This model simulates the principal phenomena governing mushy zone dynamics including solute diffusion in the interdendritic and bulk liquids, migration of both the solid-liquid interface and the...
Article
Full-text available
The macroscopic multiphase flow and the growth of the solidification microstructures in the mushy zone of a direct chill (DC) casting are closely coupled. These couplings are the key to the understanding of the formation of the macrosegregation and of the non-uniform microstructure of the casting. In the present paper we use a multiphase and multis...
Conference Paper
Full-text available
Macroscopic models of equiaxed solidification in an undercooled melt consist of conservation and constitutive relations. Currently available constitutive relations assume highly simplified envelope shapes and diffusion conditions and have not been validated. Simulation results from a previously developed mesoscopic envelope model are used to develo...
Article
We investigate and assess the capability of the mesoscopic envelope model of dendritic solidification to represent the growth of columnar dendritic structures. This is done by quantitative comparisons to phase-field simulations in two dimensions. While the phase-field model resolves the detailed growth morphology at the microscale, the mesoscopic e...
Article
Full-text available
The random packing of equiaxed dendritic grains in metal-alloy solidification is numerically simulated and validated via an experimental model. This phenomenon is characterized by a driving force which is induced by the solid-liquid density difference. Thereby, the solid dendritic grains, nucleated in the melt, sediment and pack with a relatively l...
Article
Prediction of solidification defects, such as macrosegregation and inhomogeneous microstructures constitutes a key issue for the industry. The development of models of casting processes needs to account for several imbricated length scales and different physical phenomena. For example, the kinetics of the growth of microstructures needs to be coupl...
Article
Full-text available
We used two complementary modeling approaches for the simulation of columnar growth in directional solidification of organic alloys: a phase-field model and a mesoscopic envelope model of dendritic growth. While the phase-field method captures the details of the dendritic structure and of the growth dynamics, the mesoscopic model approximates the c...
Conference Paper
Full-text available
Prediction of solidification defects like macro and mesosegregations and of microstructures constitutes a key issue for the industry. The development of models needs to account for several imbricated length scales and different physical phenomena. The goal of this presentation is to introduce the existing models and their principles. The most recen...
Conference Paper
Full-text available
The mesoscopic solidification model is based on a simplified representation of dendritic structures by their envelopes. It provides quantitative predictions of dendritic growth over a wide range of solidification conditions. Because of its low computational cost compared to microscopic (e.g., phase-field) methods, parametric studies can be performe...
Chapter
The phenomena responsible for the formation of macrosegregations, and grain structures during solidification are closely intertwined. We present a model study of the formation of macrosegregation and grain structure in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy slab. The modeling of these phenomena in DC casting is a c...
Article
The mesoscopic envelope model is a recent multiscale model that is intended to bridge the gap between purely microscopic and macroscopic approaches for the study of dendritic solidification. It consists of the description of a dendritic grain by an envelope that links the active dendrite branches. The envelope growth is deduced from an analytical m...
Conference Paper
Full-text available
In solidification processes of large industrial castings and ingots, the transport of solid in the liquid has an important effect on the final grain structure and macrosegregation. Modeling is still challenging as complex interactions between heat and mass transfers at microscopic and macroscopic scales are highly coupled. This paper first presents...
Article
Full-text available
We use two complementary modeling approaches for the simulation of columnar growth in directional solidification of organic alloys: a phase field model and a mesoscopic envelope model of dendritic growth. While the phase-field method captures the details of the dendritic structure and of the growth dynamics, the mesoscopic model approximates the co...
Article
Full-text available
We present a new method to handle a representative elementary volume (REV) with a mixture of columnar and equiaxed grains in ingot castings in the framework of an Eulerian volume averaged model. The multiscale model is based on a previously established fully equiaxed model. It consists of a three-phase (extra-granular liquid, intra-granular liquid...
Article
Full-text available
The mechanical properties of an alloy being related to its microstructure, the understanding of the mechanisms responsible for the grain structure formation in direct chill casting is crucial. However, the grain size prediction by modelling is difficult since a variety of multi-scale coupled phenomena have to be considered. Nucleation and growth of...
Article
We investigate the impact of the convective transport of inoculant particles on the distribution of the final microstructure (grain size) in grain-refined aluminum-alloy castings. We carry out numerical simulations of a casting experiment, considering the solidification of an Al–22 wt.%Cu alloy inoculated with Al–Ti–B in a side-cooled 76 × 76 × 254...
Article
Full-text available
Solutal melting was investigated in-situ by mean of high temperature laser scanning confocal microscopy. This technique enabled us to track the motion of the solid-liquid interface in order to determine the evolution of the interfacial velocity. The Cu-Ni binary system was chosen as a model case and concentric samples were fabricated from both pure...
Article
Full-text available
The growth of dendritic (treelike) crystal grains is governed by an intricate interplay between diffusion and convection of heat and solute as well as capillary and surface effects. Furthermore, it is influenced by adjacent grains due to the overlap of thermal and chemical species fields emanating from each growing grain. Originally developed by St...
Article
Full-text available
We investigate the role of the inertia of the flow through the dendritic mushy zone in the numerical prediction of channel segregations during columnar solidification. The contribution of inertia is included in the momentum transport equation through the quadratic Forchheimer correction term. The study reveals a significant influence of the Forchhe...
Chapter
The phenomena responsible for the formation of macrosegregations, and grain structures during solidification are closely intertwined. We present a model study of the formation of macrosegregation and grain structure in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy extrusion ingot. The modeling of these phenomena in DC cas...
Article
This paper describes a series of experiments performed on BM05 at the European Synchrotron Radiation Facility (ESRF), dedicated to the analysis of a mushy zone evolution in a fixed temperature gradient. A mushy zone is the partially solid/partially liquid zone that is formed when solidification proceeds with the development of dendrites, and it has...