Cyclic loading behavior, such as cyclic bending, is unavoidably involved in various forming processes and the service of end products. Understanding the mechanical behavior of magnesium (Mg) alloys under cyclic bending is essential for promoting their application. Despite existing research, the microscopic mechanisms at play during cyclic bending, specifically the slip and twinning-de-twinning (TDT), warrant further exploration, which is the innovative focus of our study. To address this need, cyclic bending tests were performed on an extruded AZ31 Mg plate with the digital-image-correlation (DIC) technology. And the texture evolution was determined through electro backscattered diffraction (EBSD) measurements. Concurrently, the crystal-plasticity-based bending-specific approach, EVPSC-BEND, incorporating the TDT scheme, is utilized to interpret the mechanisms involved in cyclic bending. The impact at the macroscopic level is manifested in asymmetric cyclic moment-curvature curves, stress-strain distribution, and shifting of the neutral layer. The developed textures at different regions of the beam and the twin volume fraction distribution further directly illustrate twinning-de-twinning behaviors. Particularly, the upper and lower halves of the beam experience very distinct cyclic behaviors simultaneously. The upper half experiences a twinning, detwinning, and twinning cycle, while the lower half experiences a twin-free, twinning, and detwinning cycle. Additionally, through modeling the cyclic bending with different initial textures, the strong texture dependence has been revealed. The behaviors of magnesium alloy beam under cyclic bending discovered in this work can shed light on the application of Mg alloys, such as forming processes and service of end product.

中文翻译：

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AZ31镁合金循环弯曲过程中的机械响应和变形机制


循环载荷行为，例如循环弯曲，不可避免地涉及各种成型工艺和最终产品的使用。了解镁（Mg）合金在循环弯曲下的机械行为对于促进其应用至关重要。尽管已有研究，但循环弯曲过程中起作用的微观机制，特别是滑移和孪晶-解孪晶（TDT），值得进一步探索，这是我们研究的创新重点。为了满足这一需求，采用数字图像相关 (DIC) 技术对挤压 AZ31 镁板进行了循环弯曲测试。纹理的演变是通过电子背散射衍射（EBSD）测量来确定的。同时，基于晶体塑性的弯曲特定方法 EVPSC-BEND 结合了 TDT 方案，用于解释循环弯曲所涉及的机制。宏观层面的影响表现为不对称循环弯矩曲率曲线、应力应变分布以及中性层的移动。梁不同区域的发达织构和孪晶体积分数分布进一步直接说明了孪晶-去孪晶行为。特别是，梁的上半部分和下半部分同时经历非常明显的循环行为。上半部分经历孪生、解孪和孪生循环，而下半部分经历无孪生、孪生和解孪循环。此外，通过对不同初始纹理的循环弯曲进行建模，揭示了强烈的纹理依赖性。这项工作中发现的镁合金梁在循环弯曲下的行为可以为镁合金的应用提供启示，例如成形工艺和最终产品的使用。