Nano- and micro-scale free volume in ultrafine grained Cu-1 wt.%Pb alloy deformed by equal channel angular pressing
Nano- and micro-scale free volume in ultrafine grained Cu-1 wt.%Pb alloy deformed by equal channel angular pressing
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DOI：
10.1016/j.actamat.2009.07.066
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发表时间：
2009-11-01
期刊：
影响因子：
9.4
通讯作者：
Wilde, Gerhard
中科院分区：
文献类型：
--
作者：
Divinski, Sergiy V.;Ribbe, Jens;Wilde, Gerhard
采用放射性示踪剂扩散测量、透射电子显微镜、聚焦离子束深度球磨和正电子湮没谱相结合的方法，研究了等通道转角挤压(ECAP)变形超细晶Cu-1wt.%Pb合金的纳米和微米级自由体积。正电子寿命谱显示存在可能与晶界状态有关的空位型缺陷和空位团。符合多普勒展宽谱探测到的正电子湮没位置同时被铜和铅原子包围，这意味着在小的铅夹杂物附近有优先形核的纳米空洞。用聚焦离子束技术可以直接观察到较大的自由体积缺陷，如纳米和亚微米尺寸的孔洞和亚微米级的裂纹。在放射性示踪剂扩散实验中，建立了液体示踪剂溶液在样品中的超快渗透。这些结果为ECAP变形的超细晶铜铅合金中开口孔洞的存在提供了明确的证据。在特定的变形条件下，在严重的变形过程中，形成了一个连通的明渠网络，它促进了液体放射性示踪剂溶液的长距离渗透。渗流孔隙率的相对体积分数估计约为2×10(-6)。(C)2009年Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Nano- and micro-scale free volumes in ultrafine grained Cu-1 wt.%Pb alloy deformed by equal channel angular pressing (ECAP) were examined by a combination of radiotracer diffusion measurements, transmission electron microscopy, depth milling by focused ion beam, and positron annihilation spectroscopy. The positron lifetime spectroscopy revealed the existence of vacancy-type defects, presumably related to grain boundary states, and vacancy clusters. The positron annihilation sites probed by coincident Doppler broadening spectroscopy are surrounded by both Cu and Pb atoms, implying preferred nucleation of nanovoids near small Pb inclusions. Larger free volume defects, such as nano- and submicron-sized pores and submicrometer cracks, were directly observed by the focused ion beam technique. Ultra-fast penetration of liquid tracer solution in the sample bulk was established in the radiotracer diffusion experiments. The results provide an unambiguous proof of the existence of open porosity in ultrafine grained Cu-Pb alloy deformed by ECAP. Under specific deformation conditions, a connected network of open channels, which promotes long-range penetration of a liquid radiotracer solution, was shown to form during the severe deformation. The relative volume fraction of the percolating porosity was estimated at about 2 x 10(-6). (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.