# Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

Max, Bertrand and San Juan, Jose and Nó, Maria Luisa and Cloué, Jean-Marc and Viguier, Bernard and Andrieu, Eric Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy. (2018) Metallurgical and Materials Transactions A, 49 (6). 2057-2068. ISSN 1073-5623

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Official URL: https://doi.org/10.1007/s11661-018-4579-2

## Abstract

In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin--Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, Ea(P718){\thinspace}={\thinspace}2.68{\thinspace}{\textpm}{\thinspace}0.05 eV, $\tau$0{\thinspace}={\thinspace}2{\textperiodcentered}10-15 {\textpm} 1 s as well as its broadening factor $\beta${\thinspace}={\thinspace}1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy

Item Type: Article hal-01985776 International peer-reviewed journal French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)Other partners > Universidad del País Vasco - Euskal Herriko Unibertsitatea - EHU (SPAIN) download 18 Jan 2019 10:42

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