The microscopic-deformation mechanisms of an extruded magnesium alloy with and without precipitates [Guinier-Preston (GP) zones] subjected to cyclic deformation were investigated by in-situ neutron-diffraction (ND) measurements and crystal-plasticity modeling. The relationship between the macroscopic-cyclic-deformation behavior and the microscopic responses (particularly twinning and detwinning) at the grain level was established. The general deformation-mechanism evolution in the solution-state (ST) sample was similar to that in the peak-aged-state (PA) sample over fatigue cycles. Both samples plastically deformed by extension twinning during compression, and by a sequential process of detwinning and dislocation motion under reverse tension. The main difference is that in the PA sample, the presence of precipitating particles constrains the twinning/detwinning behaviors, which leads to an increase in the participation of dislocation slip in the plastic deformation and then induces a strengthening effect during cyclic loading. Based on the combination of the previous in-situ ND results and crystal-plasticity model, our work provides a comprehensive analysis of the interaction between the precipitation strengthening and twinning/detwinning mechanism under the whole multi-cycle cyclic loading and their effect on the macro- and micro-mechanical behavior of the precipitate-strengthened magnesium alloys.

中文翻译：

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镁合金在循环载荷作用下的析出强化微观力学行为


通过原位中子衍射 （ND） 测量和晶体塑性建模，研究了有和没有析出物 [Guinier-Preston （GP） 区] 的挤压镁合金受到循环变形的微观变形机制。建立了宏观-循环-变形行为与晶粒水平的微观响应（特别是孪生和解缠）之间的关系。在疲劳循环期间，固溶态 （ST） 样品的一般变形机制演变与峰值老化态 （PA） 样品中的变形机制演变相似。两个样品在压缩过程中通过拉伸孪晶以及在反向张力下通过脱孪晶和位错运动的连续过程发生塑性变形。主要区别在于，在 PA 样品中，沉淀颗粒的存在限制了孪生/脱孪生行为，这导致位错滑移参与塑性变形的增加，然后在循环加载过程中诱导增强作用。结合前人的原位ND结果和晶体塑性模型，我们的工作全面分析了整个多循环加载下析出强化和孪晶/解孪生机制之间的相互作用，以及它们对沉淀强化镁合金宏观和微观力学行为的影响。