A kind of bimodal graphene oxide (GO) reinforced ZK60 Mg matrix composite, characterized by the constitutes of fine grain (FG) zones reinforced by GO and coarse grain (CG) zones, was prepared via powder thixoforming, and its microstructure was optimized through adjusting the partial remelting time to achieve a desirable strength-ductility coordination. Both the volume fractions and grain sizes of CGs could be regulated at different levels by changing the heating duration. The composite thixoformed at 60 min, having 30.1 vol% CGs with average grain size of 15.2 μm, achieves the highest yield strength of 192 MPa and ultimate tensile strength of 316 MPa, as well as a high elongation of 21.8% and toughness of 61.9 MJ m, possessing the most remarkable coordination of strength and ductility among the as-reported homogeneous-structured Mg-6Zn composites reinforced by carbonaceous nanomaterials. The macroscopic strain of the composites becomes more uniform as the remelting time increases due to the enhanced co-deformation ability between FG and CG constitutes, which contributes to higher ductility. The back stress strengthening makes a large contribution to the strengthening of the composites. Bimodal structure induced toughening, enhanced dislocation storage capability of the FG zones, and crack blunting contribute to the toughness of the composites. This work provides a promising approach for designing and fabricating bimodal-structured metal matrix composites with good comprehensive mechanical performances.

中文翻译：

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通过调节粉末触变成型重熔时间优化双峰结构镁基复合材料的微观结构和力学性能

采用粉末触变成型法制备了一种双峰氧化石墨烯（GO）增强的ZK60镁基复合材料，其特征是由GO增强的细晶（FG）区和粗晶（CG）区构成，并通过调整优化其微观结构。达到理想的强度-延展性协调的部分重熔时间。通过改变加热持续时间，可以在不同水平上调节CG的体积分数和晶粒尺寸。 60 min 触变形成的复合材料具有 30.1 vol% CG，平均晶粒尺寸为 15.2 μm，达到了 192 MPa 的最高屈服强度和 316 MPa 的极限拉伸强度，以及 21.8% 的高伸长率和 61.9 MJ 的韧性m，在所报道的碳纳米材料增强的均匀结构 Mg-6Zn 复合材料中具有最显着的强度和延展性协调。由于FG和CG成分之间的共同变形能力增强，随着重熔时间的增加，复合材料的宏观应变变得更加均匀，这有助于提高延展性。背应力强化对复合材料的强化有很大贡献。双峰结构诱导增韧、增强的 FG 区位错存储能力以及裂纹钝化有助于提高复合材料的韧性。这项工作为设计和制造具有良好综合机械性能的双峰结构金属基复合材料提供了一种有前途的方法。