Fissuration à chaud : des alliages organiques aux superalliages
نویسندگان
چکیده
Hot tearing: from organic alloys to superalloys. The appearance of solidification cracks or hot tears during casting is a serious defect. EPF-Lausanne has developed a criterion for the appearance of hot tears which is based upon a mass balance performed over the liquid and solid phases and which takes into accounts for the tensile deformation of the solid skeleton perpendicular to the growing dendrites and for the induced interdendritic liquid feeding. This model introduces a critical pressure drop beyond which cavitation, i.e., nucleation of a first void, occurs. In situ observations on transparent organic alloys point our the importance of coalescence between dendrites; indeed the mechanical rigidity of the mushy zone is completed by the appearance of solid bridges between the dendrites. Eventually, the criterion is applied successively to the semi-continuous casting of aluminium alloys, to the continuous casting of steel and to the laser treatment of superalloys.
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