Effect of dynamic strain ageing on flow stress and critical strain for jerky flow in Al-Mg alloys

IF 9.4 1区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Plasticity Pub Date : 2024-06-28 DOI:10.1016/j.ijplas.2024.104053

Surajit Samanta, Jyoti Ranjan Sahoo, Sumeet Mishra

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Abstract

A comprehensive approach addressing the flow behavior and the critical strain for the initiation of serrations in Al-Mg alloys is developed in the present work. The basic premise of the approach is that the solute atmosphere influences the friction as well as the strain hardening component of the flow stress. The friction effect of the solute cloud is modeled by considering the interplay between the characteristic solute migration time and the dislocation waiting time according to the cross-core diffusion mechanism. The impact on strain hardening is modeled by considering the apparent strengthening of the forest dislocations because of formation of solute aggregates near the vicinity of dislocation junctions. The apparent forest strengthening effect scales as the square root of the ratio of solute concentration in vicinity of the dislocation junctions and the bulk solute concentration. The modified constitutive model is validated against experimental flow curves obtained for strain rates varying over several orders of magnitude. It was observed that the modified constitutive model outperforms the standard constitutive model (considers only the friction effect of solute atmosphere) in predicting the flow curves in the dynamic strain aging domain. Furthermore, the modified constitutive model also accurately predicts the critical strain for the initiation of the jerky flow in both the normal and inverse regimes of the critical strain versus strain rate curve. Additional validation of the modified constitutive model is provided by dislocation character and density measurements via X-ray diffractograms, dislocation structure investigation via transmission electron microscopy along with fracture surface analysis.

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动态应变时效对铝镁合金中的流动应力和涩流临界应变的影响

本研究针对铝镁合金的流动行为和锯齿产生的临界应变开发了一种综合方法。该方法的基本前提是，溶质云会影响摩擦力以及流动应力的应变硬化分量。溶质云的摩擦效应是根据跨芯扩散机制，通过考虑特征溶质迁移时间和位错等待时间之间的相互作用来建模的。由于在差排交界处附近形成了溶质聚集体，因此对应变硬化的影响是通过考虑森林差排的明显增强来模拟的。表观森林强化效应的大小为差排连接附近溶质浓度与体积溶质浓度之比的平方根。修改后的构成模型根据应变率变化超过几个数量级时获得的实验流动曲线进行了验证。结果表明，在预测动态应变老化域的流动曲线方面，修正的构成模型优于标准构成模型（只考虑溶质大气的摩擦效应）。此外，在临界应变与应变速率曲线的正态和反态中，修正后的构成模型还能准确预测启动涩流的临界应变。通过 X 射线衍射图测量位错特征和密度，通过透射电子显微镜研究位错结构，并进行断裂表面分析，对修改后的构成模型进行了进一步验证。

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来源期刊

International Journal of Plasticity 工程技术-材料科学：综合

CiteScore

15.30

自引率

26.50%

发文量

256

审稿时长

46 days

期刊介绍： International Journal of Plasticity aims to present original research encompassing all facets of plastic deformation, damage, and fracture behavior in both isotropic and anisotropic solids. This includes exploring the thermodynamics of plasticity and fracture, continuum theory, and macroscopic as well as microscopic phenomena. Topics of interest span the plastic behavior of single crystals and polycrystalline metals, ceramics, rocks, soils, composites, nanocrystalline and microelectronics materials, shape memory alloys, ferroelectric ceramics, thin films, and polymers. Additionally, the journal covers plasticity aspects of failure and fracture mechanics. Contributions involving significant experimental, numerical, or theoretical advancements that enhance the understanding of the plastic behavior of solids are particularly valued. Papers addressing the modeling of finite nonlinear elastic deformation, bearing similarities to the modeling of plastic deformation, are also welcomed.