Alain Jacot

ESI Group | ESIGROUP · Product Development

In cast aluminiumAluminium products, small equiaxed grains reduceReduce the risk of hot tears and shrinkage porosities by facilitating the liquid feeding in the interdendritic liquid. Although grain refinementGrain refinement in aluminium alloysAluminium alloys is well known and widely used, grain size control is still not always guaranteed industr...

This article provides an overview of high-pressure die casting (HPDC)-related research undertaken at the EPSRC Future LiME Hub between 2015–2022. The project aimed to identify the cause of variability in the tensile ductility of die-cast structures, and to develop novel processing techniques to address this issue. Variability in tensile ductility w...

In the cold chamber high-pressure die casting (CC-HPDC) process, alloy solidification in the shot sleeve due to heat loss leads to the formation of externally solidified crystals (ESCs), which have been proven to be closely related to microstructure inhomogeneity and mechanical properties of cast components. In this paper, the solidification behavi...

This article unmasks the probabilistic nature of high-pressure die casting; specifically, the cause of scatter in the tensile ductility of die-cast Al8Si0.4Mn0.3Mg (wt.%) alloy. Scatter in tensile ductility is related to the size of large pores and non-metallic inclusions. We propose that these non-metallic inclusions form during the pyrolysis of c...

The breakup of agglomerates and bodies suspended in turbulent flows are important phenomena that influence many aspects of modern solidification processing. It is often assumed that breakup operates in high-pressure die casting, wherein molten metal is transported at high speed through a narrow orifice system. To test this assumption, X-ray tomogra...

Aimed at the mechanical property improvement in the high pressure die casting (HPDC) process for the aluminium alloy, two sets of shot curves (the baseline and the optimized condition) are designed to study their influence on the distributions of the ultimate tensile strength (UTS) and the elongation (El) for the as-cast ASTM tensile samples. Diffe...

The application of computer aided engineering (CAE) has become a trend in manufacture industry due to its great efficiency and reliability. In casting industries, numerical modelling of the casting process based on CAE has replaced traditional trial-and-error R&D procedures in many aspects. With advanced parallel computing techniques and numerous c...

Grain refinement by inoculation is widely practised in metal casting, in particular for aluminium alloys. During the last decades several modelling techniques have emerged to quantitatively predict solidification microstructures. The prediction of grain size remains however a challenge due to the complex competition between nucleation and growth, a...

The high pressure die casting process is extensively used to manufacture light metal parts with high productivity. A major drawback of the process is the relatively high variability in mechanical properties and poor repeatability between casting cycles, limiting the achievement of weight reduction through lighter design. Although it has been establ...

A comprehensive simulation approach integrating solidification, homogenization, and precipitation during aging has been used to predict the formation of γ/γ′ microstructures in the AM1 nickel-based superalloy. The particle size distribution of intradendritic γ′ precipitates after aging was calculated with a multicomponent diffusion model coupled wi...

A 3D phase-field (PhF) model has been developed to study the formation of micropores constrained to grow within a well-developed solid network. The model accounts for the equilibrium condition at triple (solid–liquid–pore) lines and the partitioning of dissolved gases. Growth of a micropore in a representative volume element taken from X-ray tomogr...

The precipitation of γ′ phase in a commercial single crystal Ni-based superalloy with different cooling rates has been investigated by atom probe tomography. Numerous irregular interconnected γ′ precipitates in the size range of ~30 to 50 nm were obtained even utilizing the fastest possible cooling rate. Diffuse γ/γ′ interface and far from equilibr...

A modelling approach is developed for the description of microstructure formation in the industrial AM1 Ni-base superalloy. Solidification and homogenization simulations are first carried out using a microsegregation model, before using the local compositions as an input for precipitation calculations, in order to characterize the influence of segr...

A multiphase-field model has been developed in order to study the evolution of micropores constrained to grow in a solid network, with a so-called pinching effect. The model accounts for the pressure difference due to capillarity between liquid and gas, the equilibrium condition at triple (solid-liquid-pore) lines, the partitioning and diffusion of...

A comprehensive particle size distribution model has been developed for the simulation of γ′ precipitation in multicomponent Ni alloys. Nucleation, growth and coarsening of the precipitates are described by a particle size distribution. The growth rate of each precipitate class is calculated with a multi-component diffusion model formulated for non...

A comprehensive modelling approach has been developed for the simulation of microstructure formation during solidification and heat treatment in Ni-base superalloys. The microsegregation taking place during solidification is simulated using the pseudo-front tracking (PFT) technique. This finite volume method calculates the concentration profiles in...

A 3D multiphase-field (PhF) model has been developed in order to study the formation of a micropore constrained to grow in a solid network (i.e., pinching effect). The model accounts for the pressure difference due to capillarity between liquid and gas, the equilibrium condition at triple (solid-liquid-pore) lines, the partitioning and diffusion of...

A three-dimensional (3-D) multiphase-field model has been developed in order to study the formation of a micropore constrained to grow in a solid network (i.e. pinching effect). The model accounts for the pressure difference due to capillarity between liquid and gas, the equilibrium condition at triple (solid–liquid–pore) lines, and the partitionin...

A phase-field model has been developed to describe the morphology of pores constrained by a dendritic solid network, and are forced to adopt complex non-spherical shapes. The distribution of the solid, liquid and gas phases was calculated with a multiphase-field approach which accounts for the pressure difference between the liquid and the gas. The...

Directional transformation of a hypo-peritectic Fe–17.5 at.% Co alloy was studied. Two consecutive phase transformations—solidification (liquid to delta ferrite) and solid-state transformation (δ ferrite to γ austenite)—were observed and compared with theory. In all experiments, the solidification front was planar and in the steady-state, and there...

Volume 22B describes the methods, models, and tools used to simulate manufacturing processes and predict the microstructure and mechanical properties of metals and metal parts. It covers a wide range of processes from melting, casting, and solidification to heat treating, welding, and machining. It also addresses powder metallurgy, additive manufac...

Volume 22B describes the methods, models, and tools used to simulate manufacturing processes and predict the microstructure and mechanical properties of metals and metal parts. It covers a wide range of processes from melting, casting, and solidification to heat treating, welding, and machining. It also addresses powder metallurgy, additive manufac...

The Cu–Ge binary system was assessed thermodynamically using the CALPHAD method through Thermo-calc® software package based on the evaluation of all available experimental data from the published literature. The solution phases, including liquid, fcc, hcp and diamond (Ge), were described by the substitutional solution model, of which the excess Gib...

A 2D phase-field model has been developed in order to describe the morphology of a pore forming within interdendritic liquid channels and the geometrical effect of mechanical contacts with neighboring solid. The distribution of the solid, liquid and gas phases is calculated with a multiphase-field approach which accounts for the pressure difference...

A phase-field model for the solid–solid α → γ transition of Ti–Al binary alloys is presented based on analytical Gibbs free energies and couplings to the thermodynamical database ThermoCalc. The equilibrium values recover the α + γ phase boundaries. Morphological transitions from diffusive to massive (partitionless) growth are observed on increasin...

This paper presents a few examples of the application of electron back-scatter diffraction (EBSD) to solidification problems. For directionally solidified Al–Zn samples, this technique could reveal the change in dendrite growth directions from <100> to <110> as the composition of zinc increases from 5 to 90 wt%. The corresponding texture evolution...

A 2D phase field model has been developed to describe the shape of a pore formed within interdendritic liquid channels. The influence of the solid, which can force the pore to adopt a non-spherical shape, is taken into account through the geometry of the domain and appropriate boundary conditions. The results show that the presence of solid call su...

A phenomenological modelling approach has been developed to describe the massive transformation and the formation of lamellar microstructures during cooling in binary γ titanium aluminides. The modelling approach is based on a combination of nucleation and growth laws which take into account the specific mechanisms of each phase transformation. Nuc...

The origin of intragranular variations of the crystallographic orientation in hot-dip Al-Zn-Si coatings is discussed based on new experimental results and modelling. The solidification microstructure in as-received 55Al-43.4Zn-l.6Si (in wt.%) coatings deposited on steel plates in an industrial production line was analyzed by electron backscattered...

A comprehensive model is presented for the simulation of microstructure evolution during industrial solidification and homogenization processing of aluminum alloys. The model combines on the one hand microsegregation due to long-range diffusion during solidification and subsequent heat treatment with, on the other hand, precipitation in the primary...

To explain the experimentally observed relation between the cooling rate and the non-equilibrium eutectic fraction obtained during solidification experiments of Al–Cu binary alloys [Eskin DG, Du Q, Ruvalcaba D, Katgerman L. Mater Sci Eng A 2005;405:1–10], a two-dimensional (2-D) microsegregation model, the pseudo-front tracking (PFT) method [Jacot...

A phenomenological modeling approach has been developed to describe the massive transformation and the formation of lamellar microstructures during cooling in gamma titanium aluminides. The modeling approach is based on a combination of nucleation and growth laws which take into account the specific mechanisms of each phase transformation. Nucleati...

The casting and repair of single-crystal gas turbine blades require specific solidification conditions that prevent the formation of new grains, equiaxed or columnar, ahead of the epitaxial columnar dendrites. These conditions are best determined by microstructure modeling. Present day analytical models of the columnar-to-equiaxed transition (CET)...

An expression for the anisotropy of the solid-liquid interfacial energy has been determined experimentally by an inverse method for the Al-43.4 wt%Zn-1.6 wt%Si system. Assuming that dendrite growth directions correspond to the minima of the surface stiffness, the anisotropy of the solid-liquid interfacial energy could be described by minimizing the...

A comprehensive model has been developed for the simulation of microstructure evolution during solidification and homogenization treatments of aluminum alloys. It combines, on the one hand, a pseudo-front tracking method for the prediction of long range diffusion during solidification and homogenization, and, on the other hand, a particle size dist...

A comprehensive model has been developed for the simulation of microstructure evolution during solidification and homogenization treatments. It combines, on the one hand, a pseudo-front tracking method for the prediction of long range diffusion during solidification and homogenization, and, on the other hand, a particle size distribution method for...

The dendrite structure and the surface appearance of hot-dip metallic coatings are strongly influenced by the interaction of the dendrite tips with the boundaries confining the melt. In order to develop a better understanding of microstructure formation in these systems, a multiscale simulation approach has been developed. The approach consists fir...

A new two-dimensional model for the simulation of microstructure formation and microsegregation during solidification of multicomponent alloys is presented. The model combines a direct simulation of the primary phase formation based on a previously published pseudo-front tracking method [Jacot A, Rappaz M. Acta Mater 2002;50:1909; Acta Mater 2002;5...

IntroductionPseudo-Front Tracking Model Primary Phase FormationSecondary Phases FormationCoupling with Thermodynamic Databases Primary Phase FormationSecondary Phases FormationCellular Automaton–Finite Element Model Nucleation LawGrowth LawCoupling of CA and FE Methods Results and Discussion PFT ModelCAFE ModelConclusion References Primary Phase Fo...

The tendency of low-concentration alloys to develop hot tears during solidification is strongly related to the ability of the primary solid phase to form a coherent network, which can withstand significant tensile or shear stresses. Coalescence, i.e. the transformation of two impinging solidification fronts into a solid bridge (or grain boundary),...

A multiphase-field model for the description of coalescence in a binary alloy is solved numerically using adaptive finite elements with high aspect ratio. The unknown of the multiphase-field model are the three phase fields (solid phase 1, solid phase 2, and liquid phase), a Lagrange multiplier and the concentration field. An Euler implicit scheme...

In the Epitaxial Laser Metal Forming (E-LMF) process, metal powder is injected into a molten pool formed by controlled laser heating with the aim of producing a single crystal deposit on a single crystal substrate. It is a near net-shape process for rapid prototyping or repair engineering of single crystal high pressure/high temperature gas turbine...

Hot tearing, a severe defect occurring during solidification, is the conjunction of tensile stresses which are transmitted to the mushy zone by the coherent solid underneath and of an insufficient liquid feeding to compensate for the volumetric change. In most recent hot tearing criteria, one of the critical issues is the definition of a coherency...

Hot tearing in castings is closely related to the difficulty of bridging or coalescence of dendrite arms during the last stage of solidification. The details of the process determine the temperature at which a coherent solid forms; i.e., a solid that can sustain tensile stresses. Based on the disjoining-pressure concept used in fluid dynamics, a th...

A two-dimensional model for the simulation of microstructure formation during solidification in multi-component systems has been developed. The formation of the primary solid phase is described using a pseudo-front tracking technique. This method permits to calculate the evolution of solid/liquid interfaces which are governed by solute diffusion an...

Hot tearing, a severe defect occurring during solidification, is induced by tensile stresses that are transmitted to the mushy zone by the coherent solid underneath. As the solid grains/dendrites are pulled apart, voids will form if the interdendritic liquid is unable to compensate for the volume changes. Based on these physical mechanisms, a fairl...

A two-dimensional model for the simulation of microstructure formation during solidification in multi-component systems has been developed. The model is based on a new pseudo-front tracking technique for the calculation of the evolution of interfaces that are governed by solute diffusion and the Gibbs–Thomson effect. The diffusion equations are sol...

A comprehensive mathematical model based on the commercial finite-element (FE) code ABAQUS has been developed to predict the evolution of temperature, microstructure, and residual stresses in cast iron castings. The thermal component of the model, applied in stage one of the analysis, is capable of simulating the formation of microstructure over a...

A two-dimensional (2-D) microstructural model has been developed for the description of the solidification of gray and white iron eutectics at the scale of a casting process. The model deals with the competition that can occur between the white and gray iron microstructures and between the columnar and equiaxed morphologies. The evolution of the vo...

A combined model which allows one to simulate all the steps of the reaustenitization process of ferrito-pearlitic plain carbon steel has been developed. The dissolution of pearlite, the transformation of ferrite into austenite and the homogenization of the carbon distribution is described with a finite volume method. The simulation is performed on...

A two-dimensional model has been developed for the description of the formation of austenite from lamellar pearlite in steel. The diffusion equation is solved in a small domain representative of a regular structure of lamellar pearlite. The solution is obtained using a finite element method with a deforming mesh and a remeshing procedure. The main...

A two-dimensional (2D) model has been developed for the prediction of diffusive phase transformations (e.g. α to γ). For that purpose, the diffusion equations are solved within each phase (α and γ) using an explicit finite volume technique formulated for a regular hexagonal grid. The discrete interface is represented by special volume elements . An...

In the first part of this work a comprehensive model of the continuous hardening of 3D-axisymmetric steel components by induction heating has been developed. In the model, the Maxwell and heat flow equations are solved using a mixed numerical formulation : the inductor and the workpiece are enmeshed with finite elements (FE) but boundary elements (...

The application of solidification theories to the case of the casting of aluminium alloys might be made difficult for several reasons. Firstly, depending upon the density of inoculant particles and cooling rate, the as-cast microstructure can be globular, globular-dendritic or dendritic. Therefore, the distribution of secondary eutectic phases is n...

A comprehensive micro-macroscopic model of the continuous hardening of 3d-axisymmetric steel components by induction heating has been developed. At the macroscopic scale, the Maxwell and heat flow equations are solved using a mixed numerical formulation : the inductor and the workpiece are enmeshed with finite elements (FE) but boundary elements (B...

Inverse methods can be used in solidification and related processes for the estimation of boundary conditions or physical properties of materials. For heat flow problems, these methods are based upon a minimisation of the errors between calculated and measured temperatures at given locations and times of the space-time domain, the calculated values...

At the intermediate mesoscopic scale of the grains, cellular automata (CA) methods can integrate nucleation and grain growth mechanisms to simulate the formation of grains during solidification. CA methods were combined with finite element heat flow calculations to predict the grain structure at the scale of a whole process. The microstructural fea...

A three-dimensional stochastic model of equiaxed solidification of eutectic alloys in the presence of convection/sedimentation is proposed. Assuming uniform temperature, the heat balance is coupled to a microscopic description of grain evolution. Grain location is chosen randomly within the solidifying volume. Grain evolution is followed by mapping...

A three-dimensional probabilistic model describing the solidification of a small specimen containing a metallic alloy of eutectic composition has been developed. For a uniform temperature, the heterogeneous nucleation of the grains is assumed to be randomly distributed within the domain. The growth kinetics of the grain interface may be that of eit...