PI & Resources
Prof. Manas V. Upadhyay (co-PI)
Dr. Eva Héripré (co-PI)
Post-Doc
Dr. Meriem Ben Haj Slama
Affiliations
- LMS, C.N.R.S., Ecole Polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128 Palaiseau Cedex, France
- MSSMat, C.N.R.S., CentraleSupéléc, 91190 Gif-sur-Yvette, France
Motivation
Most research (experimental and modeling) efforts in understanding the microstructure formation during 3D-printing or additive manufacturing (AM) of metals and alloys have been dedicated towards understanding the impact of heat-matter interactions in the melt-pool and rapid solidification. While these are important topics to study, it is equally important to understand the microstructure evolution in the heat-affected solid zone which undergoes thermal cycling. To better understand this, consider the layer-by-layer building of a single-track (one heat-source scan per layer) wall and focus on the material at a point X on a deposition layer L (>1). Immediately after the localized deposition, the material at X cools down at a very high temperature rate (ranging from 103 to 106 ℃/s). Addition of more layers (i.e. L+1, L+2, …) results in thermal cycling at X with varying temperature rates and amplitudes. The transient thermal gradients result in the formation of high-amplitude cyclic thermal stresses which must affect the microstructure at X, for example, through dislocation density evolution. At later stages of thermal cycling (i.e. during deposition of layer N >> L), a steady-state heat transfer could occur at X resulting in dynamic recovery/recrystallization.
However, so far there have been no coherent efforts to study their evolution during thermal cycling. This is important because AM materials spend most of the processing time undergoing thermal cycling. Furthermore, AM steels typically exhibit superior strength in comparison to their conventionally processes counterparts without any significant loss of ductility, and these desirable properties should be strongly affected by the microstructural activity occurring during thermal cycling.
Project aim
In this project, the aim is to monitor in-situ, and understand, the impact of thermal cycling on the evolution of the non-equilibrium AM microstructure of a stainless steel.
Main collaborators
- Lluís Yedra Cardona (MSSMat, CentraleSupélec)
- Alexandre Tanguy (LMS, Ecole Polytechnique)
- Simon Hallais (LMS, Ecole Polytechnique)