Large plasticity in magnesium mediated by pyramidal dislocations
Large plasticity in magnesium mediated by pyramidal dislocations
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由锥体位错介导的镁的大塑性
DOI：
10.1126/science.aaw2843
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发表时间：
2019-07-05
期刊：
影响因子：
56.9
通讯作者：
Shan, Zhi-Wei
中科院分区：
文献类型：
--
作者：
Liu, Bo-Yu;Liu, Fei;Shan, Zhi-Wei
更小但更具延展性延展性差是高强度轻质镁合金在汽车、火车和飞机上广泛使用的限制因素之一。尝试规避这种较差的延展性的通常方法是添加其他元素，但成本可能很高。刘等人。表明非常小的纯镁样品比以前认为的更具延展性（参见普鲁斯特的观点）。小样品抑制了导致大样品断裂的变形孪晶。避免这种机制应该可以开发高延展性的镁和其他金属合金。科学，本期第 14 页。 73；另见 p. 30 个亚微米尺寸的镁样品抑制了通常会阻碍良好延展性的变形机制。轻质镁合金作为结构材料在提高运输车辆重量等应用中的能源效率方面具有吸引力。广泛应用的一个主要障碍是镁的延展性有限，这归因于<c+a>位错无法适应塑性应变。我们通过原位透射电子显微镜机械测试证明，各种特征的<c+a>位错可以通过在锥体平面上滑动来适应相当大的塑性。我们发现亚微米尺寸的镁样品表现出高塑性，远高于块状镁样品。小晶体尺寸通常会带来高应力，进而激活镁中更多的〈c+a〉位错以适应塑性，从而获得高强度和良好的塑性。
Smaller but more ductile Poor ductility is one limiting factor in widespread use of strong but lightweight magnesium alloys in cars, trains, and planes. The usual way to try to circumvent this poor ductility is by adding other elements, which can be costly. Liu et al. show that very small samples of pure magnesium are much more ductile than previously believed (see the Perspective by Proust). The small samples suppress the deformation twinning that causes fractures in larger samples. Avoiding this mechanism should allow development of high-ductility magnesium and other metal alloys. Science, this issue p. 73; see also p. 30 Submicrometer-sized samples of magnesium suppress deformation mechanisms that normally prevent good ductility. Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to 〈 c+a 〉 dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that 〈 c+a 〉 dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more 〈 c+a 〉 dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.