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Optimisation of micrustructure and fatigue properties of Inconel 718 for extrusion die applications

Taina, Fabio. Optimisation of micrustructure and fatigue properties of Inconel 718 for extrusion die applications. PhD, Génie Mécanique, Mécanique des Matériaux, Institut National Polytechnique de Toulouse, 2011

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Abstract

This present work is a contribution to an extensive development study, promoted by Hydro Aluminium, in the field of the damage mechanisms of extrusion dies. The originality of the present work is based on the development of an optimized Inconel 718 alloy as bulk material for extrusion die., which corresponds to a new application of this alloy in the field of tools: The investigation of the impact of the so called “Material Extrinsic Parameters”, such as extrusion speed, billet length and thermo-mechanical loading on the mechanical behaviour of the material is proposed. The cyclic tensile and compressive stresses, acting on the die, are simulated by isothermal Low Cycle Fatigue (LCF) tests. Results show that strain rate and holding time have a significant impact on fatigue life. These considerations represent the “Input Data” for the design of an optimized Inconel 718 in order to adapt the material to the specific conditions imposed by the extrusion process. This objective is achieved by modifying the “Material Intrinsic Parameters” such as grain size or precipitates morphology through the formulation of alternative thermal treatments. Additional LCF tests, are carried out to compare the cyclic response of the alternative Inconel 718 grades. One of this treatment, elaborated by a multidisciplinary approach including metallurgical, chemical and mechanical experiments that has been implemented in the industrial production practice as the new standard procedure for the thermal treatment of the Inconel 718 extrusion dies.

Item Type:PhD Thesis
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Laboratory name:
Research Director:
Lours, Philippe and Delagnes, Denis
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Deposited By: Elise Gay Leboul
Deposited On:21 Sep 2016 14:14

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