This paper presents results acquired from experimental investigations into determining the influence of cyclic-bending-under-tension (CBT) and annealing on elongation-to-fracture (ETF) and tradeoffs in strength and ductility of three Mg sheet alloys: ZEK100, BioMg250, and Mg4Li. The CBT process imparts uniform deformation greater than achievable in simple tension (ST) incrementally by subjecting a sheet specimen to simultaneous tension with a crosshead motion and bending with a set of rollers reciprocating along the specimen. The space of process parameters including crosshead velocity and bending depth is explored initially to achieve the greatest ETF of ZEK100 alloy. Improvements in ETF of about 40% are attained using CBT relative to ST. Given the uniform deformation imparted by CBT to large plastic strains, tradeoffs in strength and ductility of the alloy are investigated next by subjecting the alloy sheets to a certain number of CBT cycles under the optimized parameters and subsequent annealing. Strength of the alloy is found to increase by a factor of 1.4 along the sheet strongest direction, the rolling direction, and a factor of 2 along the sheet softest direction, the transverse direction. Since the strength improved more along the soft direction than along the hard direction, the alloy anisotropy reduces. Significantly, the strength can increase for about 40% along the soft direction, while reducing the anisotropy and preserving at least 10% of the alloy ductility in every direction. Characterization of microstructural evolution using electron-backscattered diffraction and texture evolution using neutron diffraction revealed slip dominated deformation of the alloy. Similar processing and testing of BioMg250 and Mg4Li sheet alloys produced even better results in terms of enhancing elongation and improving the contrasting strength and ductility properties. Comprehensive data for the three alloys and insights from the investigations are presented and discussed.

本文介绍了通过实验研究获得的结果，以确定循环拉伸弯曲 (CBT) 和退火对断裂伸长率 (ETF) 的影响以及三种镁板合金的强度和延展性的权衡：ZEK100、BioMg250、和 Mg4Li。CBT 工艺通过使片状样品同时承受十字头运动的张力和沿样品往复运动的一组滚轮的弯曲，从而逐渐赋予大于简单张力 (ST) 所能实现的均匀变形。初步探讨了十字头速度和弯曲深度等工艺参数空间，以实现ZEK100合金的最大ETF。相对于 ST，使用 CBT 可使 ETF 提高约 40%。鉴于 CBT 赋予大塑性应变的均匀变形，接下来，通过在优化参数下对合金板进行一定次数的 CBT 循环以及随后的退火，研究合金强度和延展性的权衡。发现合金的强度沿板材最强方向（轧制方向）增加了 1.4 倍，沿板材最软方向（横向）增加了 2 倍。由于沿软方向的强度比沿硬方向的强度提高更多，因此合金的各向异性降低。值得注意的是，沿软方向强度可增加约 40%，同时降低各向异性并在每个方向上保留至少 10% 的合金延展性。使用电子背散射衍射对微观结构演化进行表征，并使用中子衍射对织构演化进行表征，揭示了合金的滑移主导变形。BioMg250 和 Mg4Li 板材合金的类似加工和测试在提高伸长率和改善对比强度和延展性方面产生了更好的结果。介绍并讨论了三种合金的综合数据以及研究的见解。