PostDoc position : Controlling Defect Formation in Recycled Aluminium Alloys through Solidification Engineering and Multi-Physics Modelling Scientific fields: Material Science, thermal simulation, Metallurgy, Solidification of alloys,...

School - Location: Centrale Lille Institute
Laboratory: LaMcube Web site: http://lamcube.univ-lille.fr/
Name of the supervisor: Amina Tandjaoui Email: amina.tandjaoui@centralelille.fr
Funding :   MSCA Postdoctoral Fellowship
Application : File deposit (no email withattached files accepted) 

Submit your ZIP file (FIRST NAME_FAMILY NAME) :
https://nextcloud.univ-lille.fr/index.php/s/ezJxfSBwTjkJCnt

Key words: solidification, recycled aluminum alloys, induction heating, thermal simulations, 3D modelling, mechanical testing.

Scientific context & project objectives:
The transition toward a circular economy requires the increasing use of recycled aluminium
alloys in structural and automotive applications. However, recycled alloys often contain
impurities (particularly iron), leading to the formation of brittle intermetallic phases and casting
defects that reduce mechanical performance and fatigue life.
Understanding and controlling the 3D microstructure and defect formation during solidification
is therefore a key scientific and industrial challenge.
However, the use of recycled alloys introduces significant challenges related to chemical
contamination and microstructural heterogeneity. During collection, sorting and remelting
processes, several impurity elements such as iron [1], copper, zinc or magnesium may
accumulate in the melt. Among these elements, iron is particularly problematic because it
promotes the formation of Fe-rich intermetallic phases, which are typically brittle and may
strongly affect the mechanical behaviour of the alloy.
In addition to chemical heterogeneities, the casting process strongly influences the
microstructure and defect population. The Lost Foam Casting (LFC) process, developed in the
1980s as an alternative to conventional gravity Die Casting (DC), offers advantages such as
reduced tooling costs and improved dimensional accuracy. However, the slower cooling rates
associated with LFC lead to:
 coarser α-Al dendritic structures,
 larger and more numerous shrinkage pores,
 modifications in eutectic silicon morphology.
These microstructural heterogeneities are known to strongly influence damage mechanisms
under mechanical and thermo-mechanical loading. In particular, casting defects such as pores
may act as preferential sites for fatigue crack initiation, while brittle intermetallic phases may
influence crack propagation paths within the microstructure.
Previous research carried out at the LaMcube laboratory [2–4] has investigated the relationship
between microstructural features, casting defects and fatigue crack initiation in recycled
aluminium alloys. These studies highlighted the importance of the three-dimensional distribution
of defects and intermetallic phases in controlling crack initiation mechanisms.
However, a major difficulty in analysing these mechanisms arises from the large variability of
defect populations in industrial castings, which makes it difficult to isolate the influence of specific
microstructural parameters.
To address this issue, the LaMcube laboratory has recently developed the SPECIMEN 3D platform,
an experimental system designed to produce aluminium alloy tensile specimens with controlled
defect distributions and tailored microstructures.
The objective of this project is to understand and control the formation of defects and
microstructural heterogeneities during the solidification of recycled aluminium alloys.
More specifically, the project aims to:
 analyse the influence of thermal gradients and cooling kinetics on defect formation
during solidification,
 control the spatial distribution of shrinkage pores within a predefined region of interest
in tensile specimens,
 investigate the influence of impurity elements and alloying additions on the morphology
of intermetallic phases and eutectic microstructures,
 provide well-controlled model specimens enabling systematic studies of crack initiation
and propagation mechanisms in recycled alloys.
By combining numerical modelling and controlled experiments, the project seeks to establish
quantitative relationships between processing conditions, microstructure and defect formation.
Description of the work & Methodology :
The project will combine multi-physics numerical simulations, casting process modelling, and
experimental validation.
The study will focus on the production of aluminium alloys tensile specimens with the SPECIMEN
3D platform. This platform is therefore equipped with an induction-heating furnace, below which
a mould will be positioned to allow casting and control of the solidification.
The first part of the work will focus on modelling the thermal behaviour of the mould-specimen
system during casting. Thermal simulations will be performed using ANSYS Fluent or COMSOL

Multiphysics in order to:
 model heat transfer within the mould and specimen,
 simulate induction heating of the mould-specimen assembly,
 evaluate temperature gradients and cooling rates during solidification.
These simulations will be used to determine the conditions required to control the solidification
front and local cooling kinetics, which are critical parameters governing pore formation.
In parallel, simulations of the mould filling and solidification process will be performed using
NovaFlow software.

These simulations will provide insight into:
 melt flow behaviour during mould filling,

 feeding conditions during solidification,
formation mechanisms of shrinkage porosity.
The results will guide the optimisation of casting parameters.
The numerical models will be validated experimentally using the SPECIMEN 3D platform. Several
engineering challenges remain to be addressed:
 adapting the induction heating system to achieve the thermal conditions predicted by
simulations,
 defining the process parameters required to control the solidification front,
 ensuring that shrinkage pores form within the targeted region of interest in the specimen
gauge.
In addition, the chemical composition of the melt will be modified during the melting stage in
order to study the influence of alloying elements such as iron and strontium on the morphology
of intermetallic phases and eutectic silicon[5,6].
At the end, the resulting specimens will be characterised using a multi-scale approach.Three-
dimensional characterization of defects will be performed using X-ray microtomography, allowing
the identification of : pore size distributions, pore morphology and spatial distribution of defects
within the specimen. At a finer scale, the microstructure will be analysed using: optical
microscopy, scanning electron microscopy (SEM) for phase identification.
These analyses will provide detailed information on the relationship between pores, intermetallic
phases, and the surrounding microstructure [7].
These final stages will be carried out by collaboration with PhD students whose funding and
recruitment are currently in progress.
Funding :
This position is offered in view of submitting a proposal to the Marie Skłodowska-Curie Postdoctoral
Fellowship programme. The selected candidate will be supported in preparing the fellowship application.

Candidate profile :
We are looking for a motivated candidate with expertise in:
Thermal or multi-physics numerical simulations

Metallurgy of alloys and solidification
Experience in casting simulation or heat transfer modelling
 3D modelling tools (CATIA, OnShape, or similar)
The candidate should demonstrate strong motivation for the proposed research, as well as good
teamwork and communication skills.
References:
[1] Li Z, Limodin N, Tandjaoui A, Quaegebeur P, Osmond P and Balloy D 2017 Influence of Sr, Fe
and Mn content and casting process on the microstructures and mechanical properties of AlSi7Cu3 alloy
Mater. Sci. Eng. A 689 286–97
[2] Wang L, Limodin N, El Bartali A, Witz J-F, Seghir R, Buffiere J-Y and Charkaluk E 2016 Influence
of pores on crack initiation in monotonic tensile and cyclic loadings in lost foam casting A31 9 alloy by
using 3D in-situ analysis Mater. Sci. Eng. A 673 362–72
[3] Dahdah N, Limodin N, El Bartali A, Witz J-F, Seghir R, Charkaluk E and Buffiere J-Y 2016 Influence
of the Casting Process in High Temperature Fatigue of A319 Aluminium Alloy Investigated By In-Situ X-
Ray Tomography and Digital Volume Correlation Procedia Struct. Integr. 2 3057–64
[4] Li Z, Limodin N, Tandjaoui A, Quaegebeur P, Witz J-F and Balloy D 2016 Damage investigation
in A319 aluminum alloy by digital image correlation during in-situ tensile tests Procedia Struct. Integr. 2
3415–22
[5] Firouzdor V, Rajabi M, Nejati E and Khomamizadeh F 2007 Effect of microstructural
constituents on the thermal fatigue life of A319 aluminum alloy Mater. Sci. Eng. A 454–455 528–35
[6] Yi J, Gao Y, Lee P and Lindley T 2004 Effect of Fe-content on fatigue crack initiation and
propagation in a cast aluminum–silicon alloy (A356–T6) Mater. Sci. Eng. A 386 396–407
[7] Limodin N, El Bartali A, Wang L, Lachambre J, Buffiere J-Y and Charkaluk E 2014 Application of
X-ray microtomography to study the influence of the casting microstructure upon the tensile behaviour
of an Al–Si alloy Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 324 57–62