State Key Laboratory of Metastable Materials Science and Technology, Yanshan University , Qinhuangdao 066004, China.
School of Materials Science and Engineering, Chongqing University , Chongqing, 400044, P. R. China.
Nano Lett. 2017 Oct 11;17(10):6117-6124. doi: 10.1021/acs.nanolett.7b02641. Epub 2017 Sep 5.
Light-weight magnesium alloys with high strength are especially desirable for the applications in transportation, aerospace, electronic components, and implants owing to their high stiffness, abundant raw materials, and environmental friendliness. Unfortunately, conventional strengthening methods mainly involve the formation of internal defects, in which particles and grain boundaries prohibit dislocation motion as well as compromise ductility invariably. Herein, we report a novel strategy for simultaneously achieving high specific yield strength (∼160 kN m kg) and good elongation (∼23.6%) in a duplex magnesium alloy containing 8 wt % lithium at room temperature, based on the introduction of densely hierarchical {101̅1}-{101̅1} double contraction nanotwins (DCTWs) and full-coherent hexagonal close-packed (hcp) particles in twin boundaries by ultrahigh pressure technique. These hierarchical nanoscaled DCTWs with stable interface characteristics not only bestow a large fraction of twin interface but also form interlaced continuous grids, hindering possible dislocation motions. Meanwhile, orderly aggregated particles offer supplemental pinning effect for overcoming latent softening roles of twin interface movement and detwinning process. The processes lead to a concomitant but unusual situation where double contraction twinning strengthens rather than weakens magnesium alloys. Those cutting-edge results provide underlying insights toward designing alternative and more innovative hcp-type structural materials with superior mechanical properties.
具有高强度的轻质镁合金由于其高刚性、丰富的原材料和环境友好性，特别适用于运输、航空航天、电子元件和植入物等应用。不幸的是，传统的强化方法主要涉及内部缺陷的形成，其中颗粒和晶界不可避免地阻碍位错运动并降低延展性。在此，我们报告了一种在室温下同时实现具有高比屈服强度（约 160 kN m kg）和良好伸长率（约 23.6%）的双相镁合金的新策略，该策略基于通过超高压力技术在孪晶界中引入高密度分级{101̅1}-{101̅1}双收缩孪晶（DCTWs）和全相干六方密排（hcp）颗粒。这些具有稳定界面特性的分层纳米级 DCTWs 不仅赋予了大量的孪晶界面，而且还形成了交错连续的网格，阻碍了可能的位错运动。同时，有序聚集的颗粒提供了补充的钉扎效应，以克服孪晶界面运动和脱孪晶过程中的潜在软化作用。这些过程导致了双收缩孪晶强化而不是削弱镁合金的同时但不寻常的情况。这些前沿成果为设计具有优异机械性能的替代和更具创新性的 hcp 型结构材料提供了基础见解。
