- The specific thermomechanical and fluid flow models developed and used by several partners have been benchmarked resulting in good confidence in their adequacy. The specific models are in many cases built in commercially available software packages but some are written in proprietary code.
- The process sensitivity has been analysed using the various thermomechanical and fluid flow models.
- Full-scale casting experiments have been performed on five aluminium alloys resulting in valuable data.
- A database of physical and thermomechanical material properties for four industrial aluminium alloys has been delivered. From this, constitutive thermomechanical material models have been synthesised.
- A database of heat transfer measurements in laboratory experiments has been delivered for a wide range of conditions and for four industrial aluminium alloys. These results conform to DC casting.
- Generalised formulae for the heat flux as a function of operating conditions have been composed.
- Friction forces between mould and ingot have been measured and related with casting events.
- Hot tears have been characterised in three alloys. Hot cracking has been simulated in-situ by E-SEM and on the Gleeble machine. 'Gleeble' experiments resulted in realistic cracked surfaces. The basic cracking mechanism is found to be liquid film separation following grain boundaries and local ductile deformation of dendrite bridges.
- A physical and numerical model of micro-/macrosegregation evolution during DC casting has been newly built and verified. The model describes micro-segregation in binary, ternary, and multi-component alloys based on mapped phase diagram data and accounts for back diffusion. The micro-segregation module is integrated in the macrosegregation model handling the heat, momentum, mass, and solute conservation. Thermosolutal buoyancy and solidification shrinkage are taken into account.
- A model has been written describing the generation, agglomeration, settling and capture of swarms of solidifying grains and their interaction with the surrounding liquid melt.
- A physical and numerical model of the development of surface segregation has been built. The surface segregation was measured in full-scale, which served to verify the developed model.
- The permeability of the mushy zone has been measured in a model alloy. Generalisation of this result towards the other alloys has been attempted by modelling of the evolution of the dendrite morphology.
- Dendritic coherency data has been delivered on all alloys of interest.
BE95-1112 Development of Predictive Tools for Aluminium ingot Casting Performance The total installed world capacity for primary aluminium production is about 18 million tons per annum, of which approximately 3.4 million is produced in Western Europe. The major casting technique applied for the production of aluminium alloy products is the Direct Chill (DC) casting of extrusion and sheet ingots.
The main limitations occurring in the DC casting process are:
- Geometrical defects (butt curl and butt swell);
- Hot tears and cold cracks;
- Micro- and macro segregation, e.g. the inhomogeneous distribution of the alloy elements at the scale of microstructure and the whole casting respectively and segregation of the alloy elements at the surface.
In the EMPACT project, research is proposed in order to obtain a method to control and minimize formation, cracking and micro/macro-segregation developments in aluminium casting of slabs and billets. This is to be accomplished by identifying basic mechanisms and quantifiable process parameters, implementation of those in numerical models, and developing predictive modelling tools. An essential next step is the combination of the actual experimental and production data with computational results in order to develop predictive tools for DC casting control.
The Empact project brings together the major European aluminium industries, leading institutes and universities in the field of metal solidification and materials science.
Funding SchemeCSC - Cost-sharing contracts
2628 AL Delft