arXiv subjects

Y. Le Bouar

Publications and source records attributed to Y. Le Bouar.

4 recordsLinked to original sources

arXiv2026

Thermodynamically consistent phase field model for hydrogen-assisted cracking

We propose a phase field model able to simulate hydrogen-assisted cracking in polycrystalline materials. Within a variational framework, the model simultaneously describes crack propagation and hydrogen segregation on crack surfaces and grain boundaries together with the associated reduction in interfacial energies. In the context of hydrogen-enhanced decohesion (HEDE) mechanisms, we demonstrate the ability of the model to capture the transition from transgranular cracking to hydrogen-assisted intergranular cracking.

cond-mat.mtrl-sci↗

arXiv2021

Atomistic simulation of martensite microstructural evolution during temperature driven $β\rightarrow α$ transition in pure titanium

Titanium and its alloys undergo temperature-driven martensitic phase transformation leading to the development of complex microstructures at mesoscale. Optimizing the mechanical properties of these materials requires an understanding of the correlations between the processing parameters and the mechanisms involved in the microstructure formation and evolution. In this work, we study the temperature-induced phase transition from BCC to HCP in pure titanium by atomistic modeling and investigate the influence of local stress conditions on the final martensite morphology. We simulate the transition under different stress conditions and carry a detailed analysis of the microstructural evolution during transition using a deformation gradient map that characterizes the local lattice distortion. The analysis of final martensite morphologies shows how mechanical constraints influence the number of selected variants and the number/type of defects in the final microstructure. We give insight on the origin and structure of different interfaces experimentally observed, such as inter-variant boundaries and antiphase defects. In particular, we show how antiphase defects originate from the two-fold degeneracy shuffling displacement arriving during the transition and how the triple junction formation drives the texture evolution when local stresses prevent a free shape change of the matrix surrounding the growing martensite nuclei.

cond-mat.mtrl-sci↗

arXiv2016

Density-based crystal plasticity : from the discrete to the continuum

Because of the enormous range of time and space scales involved in dislocation dynamics, plastic modeling at macroscale requires a continuous formulation. In this paper, we present a rigorous formulation of the transition between the discrete, where plastic flow is resolved at the scale of individual dislocations, and the continuum, where dislocations are represented by densities. First, we focus on the underlying coarse-graining procedure and show that the emerging correlation-induced stresses are scale-dependent. Each of these stresses can be expanded into the sum of two components. The first one depends on the local values of the dislocation densities and always opposes the sum of the applied stress and long-range mean field stress generated by the geometrically necessary dislocation (GND) density; this stress acts as a friction stress. The second component depends on the local gradients of the dislocation densities and is inherently associated to a translation of the elastic domain; therefore, it acts as a back-stress. We also show that these friction and back- stresses contain symmetry-breaking components that make the local stress experienced by dislocations to depend on the sign of their Burgers vector.

cond-mat.mtrl-sci↗

arXiv2008

Mastering size and shape of CoPt nanoparticles by flash laser annealing

A major step towards the understanding of intrinsic properties of nano-objects depends on the ability to obtain assemblies of nanoparticles of a given size with reduced size dispersion and a well defined shape. The control of these parameters is a fundamental challenge. In this newsletter, we present a new method to tailor in an easy way both size and shape characteristics of nanoparticles by using laser irradiation in the nanosecond regime.

physics.atm-clus↗