Fluage à haute température de l'eutectique AlSi mise en évidence de eeux régimes d'écoulement à l'aide de l'équation de Dorn modifiée

Abstract

High temperature creep of the AlSi eutectic alloy was studied over a large stress range and it was shown that the abnormal variations of the creep rate sensitivity coefficient n to the stress, and of the apparent activation energy Q, can be rationalised if the variations of the effective stress σ ∗ with applied stress and temperature are taken into account. It was shown that the analysis of the results by the modified Dorn equation < middot|kT/DGb = A ∗(σ ∗/G) n∗ is not incoherent provided an appropriate diffusion coefficient is chosen. It was also shown that the aluminium-rich solid solution controls the strain flow and that two types of flow are taking place, one of them being superplastic with n ∗ = 1.75 at low stresses. At higher stresses a solid-solution-type viscous flow is observed with n ∗ = 3 and A ∗ ≅ 1 .