Physical Metallurgy, Advanced Microstructures, Properties
The OR 2MP is based on cross-disciplinary expertise in metallurgy. The objectives include: formulation and design of new alloys, design of innovative microstructures from bulk materials, understanding of mechanical properties and underlying deformation mechanisms, and optimization of the use properties of materials developed elsewhere.
The research carried out is strongly experimental in nature, but is closely linked (co-supervised theses, ANR projects, etc.) with the other research groups of the axis. This research is based on the implementation of conventional and non-conventional metallurgical processes of elaboration (powder metallurgy, thermomechanical treatments), microstructural transformation (post-treatments) and observation and analysis of the mechanisms of plasticity at the origin of macroscopic mechanical behaviors.
The activities focus on improving properties, sometimes antagonistic, such as mechanical strength and ductility, via the design and optimization of microstructures, with the aim of proposing material solutions, in particular for the transport, defense and biomedical industries.
These activities are divided into 3 main themes detailed below:
- Multi-main element alloys with high mixing entropy (HEA).
- Metallic materials with harmonic microstructures and grain size gradient.
- Optimization & post-processing.
Multi-major element alloys with high mixing entropy (HEA)
To meet the demand for materials with better performance, new concepts of materials development are needed. Among them, the design of alloys from multi-main elements (as opposed to conventional dilute alloys) appears as a powerful strategy to develop new materials with improved properties. The work carried out in this framework focuses on the formulation and design of multi-main element refractory alloys with high mixing entropy, as well as the evaluation of their mechanical properties (quasi-static, dynamic, fatigue) and the associated deformation mechanisms.
Metallic materials with harmonic microstructures and grain size gradient
Mechanical strength and ductility are two antagonistic concepts in conventional metallurgy. Making them cohabit in pure metals or diluted alloys has always been a subject of permanent research. One of the keys consists in delocalizing the deformation in order to delay the plastic instability. The aim is to develop a methodology to design, thanks to the versatility of powder metallurgy combined with severe plastic deformation processes (SPD) and/or large deformations (in part in inter-axis collaboration with the OR ETMHP, MINOS axis), microstructures likely to generate a plasticity gradient, for a synergy between mechanical strength and ductility.
Classic structure of a Harmonic Titanium alloy. The large grains (the core) are grouped in clusters and surrounded by smaller grains (the shell).
Optimization & post-processing
The theme proposes to explore two ways of post-processing on materials obtained by conventional or non-conventional methods (metal additive manufacturing), allowing to optimize the properties of use. The materials mainly concerned are titanium alloys. The envisaged research will be centered on the development of processes of : (i) microwave plasma oxidation treatment. The objective is to improve tribological properties by proposing cleaner and more efficient surface treatments on metal (inter-axis collaboration with the OR Plasma/Surface Interaction and Microplasmas, PPANAM axis); (ii) post-treatment by CIC on parts produced by additive manufacturing in order to reduce porosity, residual stresses and possibly anisotropy and to improve the life span of the parts thus manufactured.