Microstructure changes in HPT-processed copper occurring at room temperature
Microstructure changes in HPT-processed copper occurring at room temperature
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DOI：
10.1016/j.matchar.2019.03.046
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发表时间：
2019-05-01
影响因子：
4.7
通讯作者：
Sklenicka, V.
中科院分区：
文献类型：
--
作者：
Kral, P.;Stanek, J.;Sklenicka, V.
本文研究了超细晶(UFG)铜在室温下的长期稳定性。在室温下对纯铜试件进行了10转的高压扭转处理。这一过程对材料样品施加了约300的等效应变。在这些大应变的区域，出现了晶粒度细化的饱和。UFG铜变形到组织饱和区，然后在室温下进行6年的退火热处理。用二维和三维电子背散射衍射(EBSD)和透射电子显微镜研究了HPT处理铜的组织变化，发现HPT晶粒度饱和的铜在室温下长期存放后，UFG组织明显粗化。对晶界体积的分析表明，粗晶界通常含有具有符合位点阵(CSL)、Sigma 3和Sigma 9的平坦段。取向错位分布表明，退火组织中的大部分晶界是这类低能晶界。然而，在显微组织中也可以发现被随机边界包围的细晶群。此外，还对3D EBSD数据进行了分析，以获得统计的微观结构信息。显微组织中含有大量的细晶，但它们只占所研究体积的一小部分。描述和解释了包括CSL在内的晶界的定量几何特征。
In the present work, the long-term stability of ultrafine-grained (UFG) copper at room temperature was investigated. The pure copper specimen was processed by 10 revolutions of high-pressure torsion (HPT) at room temperature. This procedure imposes an equivalent strain of about 300 to the material sample. In the region of these large strains, a saturation in grain size refinement occurs. UFG copper, deformed up to the region of microstructure saturation, was subsequently annealed at room temperature for 6 years. Microstructure changes of HPT-processed copper were investigated by means of 2D and 3D electron back scatter diffraction (EBSD) and also by transmission electron microscopy.It was found that the UFG microstructure of copper with saturated HPT-grain sizes coarsens significantly during long-term storage at room temperature. The analysis of grain volumes showed that the boundaries of coarse grains often contain flat segments with the coincidence site lattices (CSL) Sigma 3 and Sigma 9. The misorientation distributions revealed that most boundaries in the annealed microstructure are low energy grain boundaries of these kinds. However, groups of fine grains that are surrounded by random boundaries can also be found in the microstructure. Furthermore, 3D EBSD data were analysed in order to obtain a statistical microstructural information. The microstructure contains a high number of fine grains, but they form only a minority of the investigated volume. Quantitative geometrical characteristics of grain boundaries including CSL were described and interpreted.