Open PhD position: “Microstructural changes in additive manufacturing materials during Hot Isostatic Pressing: modelling and experimental study”

Additive manufacturing (AM) processes are promising techniques for manufacturing metallic components from powder or wire feedstock. AM materials exhibit microstructures very different from cast or forged equivalent materials. They are out of equilibrium, sometimes anisotropic, with specific features like a high dislocation density and defects (unmelted particles, pores) which may be detrimental to mechanical properties (creep, fatigue resistance). Defects can be mitigated using a heat treatment under high gas pressure (hot isostatic pressing HIP), at the expense of material softening.

The objective of the PhD thesis is to model the microstructural évolutions during HIP in order to optimise the HIP cycle for a given AM microstructure: defects shall be decreased enough while softening shall be limited.

A detailed characterisation of the initial microstructure will be done (defects, grain size, dislocation density, precipitates, texture…) in order to provide data for the DIGIMU software. This software uses the level set method to simulate, by finite element calculation, the evolution of a volumic element representative of a microstructure during thermomechanical loading. This software will be enriched. The comparison between modelled evolution and experimentally observed ones will be used to assess the relevancy of the modelling (HIP will be applied on samples). Furthermore, attention will be paid to the evaluation of the impact of the HIP treatment on mechanical properties of AM material (316L steel will be used).