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首页> 外文期刊>Physica, B. Condensed Matter >Free volumes in bulk nanocrystalline metals studied by the complementary techniques of positron annihilation and dilatometry
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Free volumes in bulk nanocrystalline metals studied by the complementary techniques of positron annihilation and dilatometry

机译：通过正电子an没和膨胀计的互补技术研究块状纳米晶体金属的自由体积

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摘要

Free-volume type defects, such as vacancies, vacancy-agglomerates, dislocations, and grain boundaries represent a key parameter in the properties of ultrafine-grained and nanocrystalline materials. Such free-volume type defects are introduced in high excess concentration during the processes of structural refinement by severe plastic deformation. The direct method of time-differential dilatometry is applied in the present work to determine the total amount and the kinetics of free volume by measuring the irreversible length change upon annealing of bulk nanocrystalline metals (Fe, Cu, Ni) prepared by high-pressure torsion (HPT). In the case of HPT-deformed Ni and Cu, distinct substages of the length change upon linear heating occur due to the loss of grain boundaries in the wake of crystallite growth. The data on dilatometric length change can be directly related to the fast annealing of free-volume type defects studied by in situ Doppler broadening measurements performed at the high-intensity positron beam of the FRM II (Garching, Munich, Germany).
机译：空体积型缺陷，如空位，空位团聚，位错和晶界代表超细晶粒和纳米晶材料性能的关键参数。这种自由体积型缺陷在结构改进过程中由于严重的塑性变形而以高过量浓度引入。在本工作中采用时差膨胀法的直接方法，通过测量高压扭转法制备的块状纳米晶体金属（Fe，Cu，Ni）退火时不可逆的长度变化，来确定总量和自由体积动力学。 （HPT）。在HPT变形的Ni和Cu的情况下，由于微晶生长后晶界的损失，出现了线性加热时长度变化的明显子阶段。膨胀长度变化的数据可以直接与自由体积型缺陷的快速退火相关，该快速退火是通过在FRM II（Garching，慕尼黑，德国）的高强度正电子束上进行的原位多普勒展宽测量研究的。

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