基于调控初始织构分布改善镁合金板材室温弯曲成形性能的机理研究

Magnesium alloys are one of the most promising lightweight structural materials. However, wrought magnesium alloy sheets usually show poor bending formability at room temperature owing to the strong c-axis∥ND basal texture formed during their primary forming processes, which severely restricts their applications as structural components. Therefore, this project proposed a novel idea that the room-temperature bendability of Mg sheets can be optimized by tailoring the distribution of basal texture. By means of regulating the texture distribution, the plastic deformation mechanisms introduced in the inner and outer layers during room-temperature bending process can be enriched, and the deformation abilities as well as the symmetry of strain compatibility in the inner and outer bending regions can be enhanced effectively. These optimizations are expected to improve the final room-temperature bendability of Mg sheets. In this study, the room-temperature bendability of a series of Mg sheets with different initial texture distributions are intended to studied systematically. The selection and evolution of deformation mechanisms in the inner and outer layers of these sheets during bending is investigated by using the in-situ EBSD and TEM characterization methods. Additionally, the stress-strain field of the sheets with different initial texture distributions during whole bending process are established by finite element modelling, to revel the selection mechanism of the various deformation mechanisms, as well as to analyze the influence of the mechanism selection on the deformation ability and the strain compatibility of the bending regions. These investigations aim to reveal the internal logic relations between the initial texture distribution, the evolution of micro plastic deformation mechanisms and the final macro room-temperature bendability of Mg sheets. Through the above research work, the principle of texture modification process for improving the bendability of Mg sheets is intended to be proposed. Additionally, orientation models of the Mg sheets which possess high room-temperature bendability are intended to be established as well as their relevant preparation technologies are tried to be developed. Overall, this study is designed to provide theoretical and experimental basis on the improvement of room-temperature bendability of wrought Mg sheets, and thus to expound their practical applications.

镁合金是最具开发前景的轻质结构材料之一，然而受制于制备中产生的c-axis∥ND强基面织构，板材表现出较差的室温弯曲成形能力，应用受到极大限制。对此，本项目提出改性并利用织构而非弱化织构的改善新思路：通过调控初始织构分布，丰富弯曲成形时内外侧变形机制选择，优化内外侧应变协调能力及其对称性，以提升镁板室温弯曲成形性能。拟通过制备一系列不同初始织构分布的镁板，采用弯曲成形的原位EBSD表征结合TEM分析，研究其内外侧变形机制的选择及演变特性；通过有限元模拟建立弯曲成形的应力应变场，深入分析不同初始织构分布镁板弯曲成形时变形机制的选择机理，并分析其内外侧变形机制对于应变协调能力及其对称性的影响。从而揭示镁板弯曲成形时初始织构分布、微观变形机制及宏观成形能力之间的内在关联，提出基于调控织构分布改善镁合金板材室温弯曲成形性能的优化原则和技术原型，为改善镁板室温弯曲成形能力提供理论指导和实验基础。

镁合金是最具开发前景的轻质结构材料之一，然而受制于制备生产中引入的c-axis∥ND强基面织构，板材通常表现出较差的室温弯曲成形能力，应用受到极大限制。探究提升镁合金板材室温弯曲成形能力，发展创新的室温高弯曲成形性板材先进制备理论，是目前镁合金研究领域的关键热点。对此，本研究提出改性并利用织构而非弱化织构的改善新思路：通过调控初始织构分布，丰富弯曲成形时内外侧变形机制选择，优化内外侧应变协调能力及其对称性，以提升镁合金板材室温弯曲成形性能。本研究通过制备出5种不同初始织构分布的AZ31镁合金板材，采用EBSD精细表征技术，研究不同初始织构分布板材在弯曲时内外侧变形机制的选择及演变特性；结合三点弯曲时样品各区域的应力应变状态，深入分析了不同初始织构分布镁合金板材弯曲成形时变形机制的选择机理，并分析其内外侧变形机制对于应变协调能力及其对称性的影响。从而揭示了镁板弯曲成形时初始织构分布、微观变形机制及宏观成形能力之间的内在关联，提出了基于调控织构分布改善镁合金板材室温弯曲成形性能的优化原则和技术原型，为开发室温高弯曲成形性能镁合金板材提供了有效的理论指导和实验基础。