TEGHRI AsmaNGUYEN THI Henri (Encadrant)REINHART Guillaume (Encadrant)BENOUDIA Mohamed Cherif (Encadrant)2024-05-222024-05-222023http://dspace.ensti-annaba.dz:4000/handle/123456789/131Quantitative analyses were carried out in order to characterize the Columnar-to-Equiaxed Transition (CET) from solidification experiments conducted with the laboratory device SFINX (Solidification Furnace with IN situ X-radiography). The increase in constitutional undercooling that induces the nucleation of the first grains ahead of the columnar front can be related to the rapid thermal change following the increase in cooling rate. Equiaxed grain nucleation occurs in a limited range of distances that is correlated to the refining particle size and the solutal layer extent. Both mechanical and solutal blocking mechanisms were observed at CET, however, the mechanical blocking is the preponderant blocking mechanism.enThesis