Transient behaviour of electrovortex flow in a cylindrical container

K. Patouillet - L. Davoust - O. Doche

University Grenoble Alpes, CNRS, Grenoble INP, SIMaP, 38402 Saint Martin d'Héres, France

Abstract
The mechanical behaviour of the oxide film that develops at the metal-air interface of molten A356 aluminum alloy is investigated in relation to the oxidation level. Based on two previous papers - the first one focusing on the chemical aspects of the oxidation process at the liquid surface of molten aluminum, the second one focusing on its mechanical characterization, the present paper aims at reconciling these two approaches usually considered separately in the literature and proposes a stand-alone mechano-chemical model. The oxidation process is first characterized from thermogravimetric analyses together with scanning electron microscopy imaging. Then the mechanical properties of the oxide layer are determined at a given oxidation level, making use of a new annular MHD surface viscometer placed inside a chemical reactor. The kinetic study delivers a better understanding of the oxidation process involved at the surface of the A356 alloy and leads to the development of a revised version of the Deal−Grove model. In addition, the mechanical study reveals the highly viscous and shear-thinning behaviours of the oxide layer. Figs 3, Refs 14.

Key words: aluminum casting, surface oxidation, logarithmic kinetics, slip and no-slip, low-Rm MHD, surface viscosity.