Ongoing research projects

IMMC

Ongoing research projects in iMMC (July 2020)


This a short description of research projects which are presently under progress in iMMC.
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List of projects related to: metallic alloys




Development of high-toughness cryogenic alloys
Researcher: Alvise Miotti Bettanini
Supervisor(s): Pascal Jacques

Materials that can perform at extremely low temperatures are in great demand. Applications span from tanks and pressure vessels for LNG (Liquefied Natural Gas) carriers to structural materials in extreme conditions, like the upcoming exploration of Mars. In this context, it is critical to ensure very high toughness, which measures the resistance to crack propagation, at cryogenic temperatures. In this project, the experimental development of Fe-based superalloys is guided by a CALPHAD-based methodology, which allows the calculation of phase stability and phase transformation with computational models in order to reduce the experimental effort and hasten the development cycle of new materials.



Characterization and physics based modeling of plasticity and fracture of Dual-Phase steels towards ultratough materials by microstructure optimization
Researcher: Karim Ismail
Supervisor(s): Thomas Pardoen, Pascal Jacques

The research work, in collaboration with company ArcelorMittal, is about the plasticity, the damage and the crack propagation resistance of dual-phase steels, which are commonly used in the automotive industry. A minimum level of fracture toughness is required to prevent the propagation during forming operations of small edge damage or cracked zones induced by cutting. Therefore, unravelling the relationship between fracture toughness, microstructure and damage mechanisms is essential to develop advanced steels with superior forming ability. Furthermore, reaching superior fracture toughness could open to other potential applications.
Experimental works as well as computational modeling are used to study the behavior of such steels. A model for the plastic behavior and for the damage mechanisms related to the microstructure has been developed. A finite element based unit cell approach is used to address the plastic behavior, locally as well as at the macroscopic scale. A particular focus is put on the effect of particle morphology and orientation that have not been much investigated and that considerably affect local mechanical fields, and hence damage and fracture behavior. A two-stage void coalescence process is suggested in elongated microstructures. The data extracted from the elastoplastic analysis are fed into a cellular automaton approach of the damage evolution. This model introduces a statistical description of the material while using relatively simple damage evolution laws. Furthermore, the essential work of fracture method is used to quantify the resistance to the propagation of a crack on thin sheets. Martensite morphology in the form of platelets seems to be a means to reach a high fracture toughness. Finally, damage mechanisms are observed post-mortem and hole expansion ratio tests will be performed.



CeraMAX / Aerostream
Researcher: Matthieu Marteleur
Supervisor(s): Pascal Jacques

I am currently working on the processing and characterisation of a particular type of ceramics called MAX phases. They present an intermediate behavior between a ceramic and a metal at high temperature, providing a unique combination of functional properties.
My research projects also include Additive Manufacturing on metallic materials, particularly Al and Ti alloys. I am studying the relationship between the process parameters and the resulting microstructure and properties.



DeltaT
Researcher: Valentin Marchal-Marchant
Supervisor(s): Pascal Jacques

obtained his degree in engineering in materials science from the Université catholique de Louvain in 2011. Then, he accomplished his PhD under the supervision of prof. Pascal Jacques, on the study of Physical Vapor Deposition of thick copper films on steel.

His research is now focused on the development of thermoelectric materials and thermoelectric generators for energy harvesting and passive electromechanical systems. It aims at using common and non-toxic materials to generate electrical power from thermal gradients. Nowadays, attention is put on large scale applications owing to more than 7 years of research about thermoelectric materials leaded in IMAP.

The big challenge of this topic is the development of new tools and equipments for material production and assembly, and specific characterization methods. Such a wide range of different tasks can only be achieved thanks to the versatility of technical and scientific expertises of the IMAP team members as well as Lacami support.



Study of the hardening properties, damage resistance and toughness of a new family of beta metastables titanium alloys
Researcher: Laurine Choisez
Supervisor(s): Pascal Jacques

The association of different plastic deformation modes (TRIP, TWIP) induces unmatched levels of mechanical properties in a new beta metastables titanium alloys family. A hardening beyond the theoretical limit is especially noticed, together with a uniform deformation 3 to 4 times higher than the one in a classic TA6V alloy and a yield stress superior of 30 percent to the one in a
TWIP alloy. A positive synergy is thought to exist between a high hardening and the damage resistance and toughness of such materials. My thesis will consist in the study of the damage resistance and the toughness of several beta metastables titanium alloys with different prevailing plastic deformation mechanisms in order to highlight the mechanism responsible of the post-necking deformation properties.



Locoted
Researcher: Geoffrey Roy
Supervisor(s): Pascal Jacques

Geoffrey holds a Master in Mechatronic Engineering (2010) and a PhD in Engineering (2015) from the Université catholique de Louvain where he works as a senior researcher at the Institute of Mechanics, Materials and Civil Engineering (iMMC).
Within the Division of Materials and Process Engineering (IMAP), his research is focused on the development of new thermoelectric materials and systems for a range of applications going from industrial waste heat recovery to autonomous powering of smart sensors. In his research, he pays particular attention to the development of new solutions that present improved both technical and economical profiles in order to facilitate the emergence of these solutions out of the lab.
This research is followed by several companies such as: Drever International, AGC Glass Europe, Carmeuse or Engie.



Aerostream and IAWATHA (additive manufacturing), LOCOTED (thermoelectrics)
Researcher: Camille van der Rest
Supervisor(s): Pascal Jacques, Aude Simar

Camille van der Rest completed her PhD thesis on the optimisation of Heusler Fe2VAl-based thermoelectric compounds through innovative metallurgical processing in 2015. It was under the joint supervision of Prof. Pascal Jacques and Prof. Aude Simar. Her research topics now concern thermoelectric materials, additive manufacturing and friction stir processing technologies. Concerning thermoelectrics, the main objective is the development of low-cost, non-toxic, and powerful materials that could be used in large-scale industrial applications of heat recovery. In addition, she studies some fundamental aspects in order to improve the performances of such materials, i.e. ordering phenomena in off-stoichiometric Fe2VAl-based Heusler compounds. It is essential to make the link between (innovative) manufacturing processes, microstructures and the functional properties of these TE materials. Concerning additive manufacturing, the main contributions are on the characterisation and optimisation of the microstructures and the mechanical behaviour of Al parts obtained by Selective Laser Melting and the developpment of new materials for additive manufacturing. Again, the link between the process parameters and the final microstructure/properties is a key issue. Finally, Camille developed, together with Prof. Aude Simar and Prof. Pascal Jacques, a novel Friction Melt Bonding (FMB) process in order to weld aluminium alloys and steels. This process is still under development thanks to the collaboration with other researchers of IMAP.



RESTEAR
Researcher: Thaneshan Sapanathan
Supervisor(s): Aude Simar

completed a mechanical engineering degree and a PhD at Monash University (Australia) in 2010 and 2014, respectively. His thesis was entitled “Fabrication of axi-symmetric hybrid materials using combination of shear and pressure”. During his PhD, he worked on architectured hybrid materials fabrication using severe plastic deformation (SPD) processes. Two novel axi-symmetric SPD techniques were investigated to fabricate hybrid materials with concurrent grain refinements. After that, he started a research project at University of Technology of Compiègne (France) in which he investigated the weldability window for similar and dissimilar material combinations using numerical simulations for magnetic pulse welding. He also studied the interfacial phenomena, behavior of material under high strain rate deformation, modeling and simulation of the magnetic pulse welding/forming. Then, I was working as a postdoctoral research fellow at UCL on the topic of characterizations of aluminium to steel welds made by friction stir welds and friction melt bonding. At present, I am working as a FNRS reserch officer (Chargé de recherche) and investigating intermetallic induced residual stresses and mitigation of hot tear in innovative dissimilar joints.



Friction stir processing based local damage mitigation and healing in aluminium alloys
Researcher: Matthieu Baudouin Lezaack
Supervisor(s): Aude Simar

Al 7XXX alloys will be characterized before and after friction stir process (FSP) in order to identify the damage mechanisms. The performances of FSPed alloys will be studied by macromechanical testing. Up to now, a 150% increase in ductility was reached by FSP + heat treatments compared to the base 7475 Al material. Then a numerical model will catch the 7XXX aluminium behavior in a close future.



Influence of defects on the life of biomedical implants
Researcher: Maïté Croonenborghs
Supervisor(s): Pascal Jacques, Thomas Pardoen

Implants are devices aiming to support, help or even correct biological structures. However, with time, some of these implants show aging problems. The roots of these problems can have numerous explanations. In some cases, the body reacts to the presence of a foreign body, and this can lead to health risks. Sometimes, the material can show, with time, signs of weakness. Later on, these defects can lead to the failure of the implant.
In the case of permanent stent implants, the presence of a foreign body in the blood vessels can lead to restenosis or late thrombosis. This is why bioresorbable stents are nowadays developed. These stents should support the vessels during their healing period and dissolve in an inoffensive way afterwards. Iron-based alloys are investigated for their appropriate mechanical properties but their degradation rate is too low. One investigated solution is to increase surface roughness to dissolve faster the implant. The effect of this roughness on the expansion process has not been analyzed for now.
The case of growth rods shows that the material itself can lead to implant failure. These rods are placed, during a surgery, along the spine of scoliotic children. They aim to support the spine and help it to straighten back. However, fracture events occur in 36% of the patients. During the surgery, the rods are bent to fit to the natural shape of the spine. The tools employed for this process can introduce some indentation marks on the surface of the rods and decrease their fatigue lifetime.
From these case studies, it is observed that the completion of an implant (i.e. stent implantation process) or its lifetime (i.e. growth rod failure) can be affected by its surface state. This research will therefore focus on the imperfection sensitiveness of such devices. Various kinds of defects are introduced at the sample surface. To understand the influence of these defects on the mechanical properties, these samples are tested and compared.



Fracture toughness of high entropy alloys
Researcher: Antoine Hilhorst
Supervisor(s): Pascal Jacques, Thomas Pardoen

High entropy alloys (HEAs) are a new family of metallic alloys. In contrast to conventional alloys, HEAs have multiple principal elements e.g. the equiatomic "Cantor" alloy CrMnFeCoNi. Alloys in this range of chemical composition have gathered attention only recently. From what was observed in conventional alloys, it was expected that HEAs microstructure be composed of several intermetallic phases but some systems are surprisingly single phase solid solution. Moreover, such single-phase alloys have excellent mechanical properties. For instance, CrMnFeCoNi possess a large fracture toughness, which increases with decreasing temperature, putting this alloy on par with the current best alloys used for cryogenic applications. As such, the objective of the thesis is to understand the underlying mechanisms responsible for the observed macroscopic behavior of such alloys.


The thesis aims to answer several questions such as: What are the mechanisms responsible for the increase in ductility, strength, and fracture toughness with decreasing temperature? What high-throughput methodology would be able to screen the vast range of possible chemical composition of HEAs for high performance alloys?


To understand the deformation mechanisms, several HEAs will be fully characterized from casting to mechanical testing. For the fracture toughness measurements, the essential work of fracture method will be employed as it is best suited for ductile thin sheets than compact tests. Diffusion multiples will be explored as a possible high-throughput method, as the presence of composition gradients allows the simultaneous characterization of a range of composition by techniques such as EDX, EBSD and nano-indentation.