Purpose

The purpose of this paper is to systematically investigate the dynamic strain aging (DSA) effect in solid solution treated IN718 at different temperatures through experiments and simulations to gain an understanding of the inelastic deformation mechanisms.

Design/methodology/approach

In the present work, uniaxial tensile tests have been carried out in conjunction with finite element (FE) simulations to investigate the behaviour of the solid solution treated Inconel 718 superalloy at different temperatures and strain rates. Dynamic strain aging (DSA) effects, which manifested during the tests in the form of a negative strain rate sensitivity and stress serrations, are investigated. The most significant DSA effect occurs at 500°C and at a strain rate of 10–4 s-1. In a newly proposed rate-dependent constitutive formulation, the DSA model, proposed by McCormick, Kubin and Estrin, was introduced into slip-assisted solute hardening, and an activation energy-dependent exponential flow rule was adopted.

Findings

The observed negative strain rate sensitivity and stress serrations are well predicted by a 3 D FE. The FE results indicate that the equivalent plastic strain rate distribution in the specimen gauge length is as highly inhomogeneous as in the other materials exhibiting DSA effects such as aluminium and titanium alloy. During inelastic deformation, propagating high strain rate bands can be closely correlated to the stress serrations.

Originality/value

For the DSA effect in solid solution treated IN718, the existing researching mainly focuses on the mechanical properties experiment and microstructure observation. In this study, a constitutive formulation, combined with the DSA model, has been proposed, and the mechanical behaviors, including the DSA effect, have been well predicted by a finite element model.

中文翻译：

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固溶处理的Inconel 718高温合金动态应变时效行为的实验和数值研究

目的

本文的目的是通过实验和仿真系统地研究固溶处理的IN718在不同温度下的动态应变老化（DSA）效应，以了解非弹性变形机理。

设计/方法/方法

在目前的工作中，已经结合有限元（FE）模拟进行了单轴拉伸试验，以研究固溶处理的Inconel 718高温合金在不同温度和应变速率下的行为。研究了在测试过程中以负应变速率敏感性和应力锯齿形式表现出来的动态应变老化（DSA）效应。最显着的DSA效应发生在500°C和10–4 s-1的应变速率下。在新提出的速率依赖型本构关系公式中，将由麦考密克，库宾和埃斯特林提出的DSA模型引入滑移辅助溶质硬化，并采用了依赖于活化能的指数流规则。

发现

通过3 D FE可以很好地预测观察到的负应变速率敏感性和应力锯齿。有限元结果表明，试样标距上的等效塑性应变率分布与表现出DSA效应的其他材料（如铝和钛合金）一样高度不均匀。在非弹性变形过程中，传播的高应变率带可能与应力锯齿密切相关。

创意/价值

对于IN718固溶处理的DSA效应，现有的研究主要集中在力学性能实验和显微组织观察上。在这项研究中，提出了一种与DSA模型结合的本构公式，并且通过有限元模型很好地预测了包括DSA效应在内的力学行为。