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Seyed Moien Faregh, Ghader Faraji, Mahmoud Mosavi Mashhadi, and Mohammad Eftekhari, Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion, Int. J. Miner. Metall. Mater., 29(2022), No. 12, pp.2241-2251. https://dx.doi.org/10.1007/s12613-022-2514-4
Seyed Moien Faregh, Ghader Faraji, Mahmoud Mosavi Mashhadi, and Mohammad Eftekhari, Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion, Int. J. Miner. Metall. Mater., 29(2022), No. 12, pp.2241-2251. https://dx.doi.org/10.1007/s12613-022-2514-4
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静压循环膨胀挤压后超细/纳米晶粒纯铜管的织构演化与力学各向异性

摘要: 采用静压循环膨胀挤压工艺(HTCEE)加工超细粒纯铜管,研究了其织构演化和力学各向异性行为。对于超细晶铜(UFG)管,在纵向和周向记录了不同的变形行为和显著的拉伸性能各向异性。研究结果表明HTCEE工艺使材料轴向的屈服强度和极限强度分别提高了3.6倍和1.67倍。同时,这一过程使周向的屈服强度和极限强度分别提高了1.15倍和1.12倍。作为力学各向异性判据的周向极限抗拉强度与轴向极限抗拉强度之比,对于退火粗晶粒和热处理后的UFG管分别为1.7和1.16。因此,结果表明HTCEE过程对力学各向异性有降低作用。此外,HTCEE工艺在两个方向上的延性损失都很低,这是HTCEE工艺的另一个优点。硬度测量显示,周向硬度值略有增加,这与拉伸试验的趋势一致。进行织构分析,以确定晶粒的分布,得到的111极点图证明了织构的演化,并证实了力学性能的各向异性。扫描电镜(SEM)显示,在两个正交方向拉伸试验后,出现了不同的断裂模式。

 

Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion

Abstract: Texture evolution and mechanical anisotropic behavior of an ultrafine-grained (UFG) pure copper tube processed by recently introduced method of hydrostatic tube cyclic expansion extrusion (HTCEE) was investigated. For the UFG tube, different deformation behavior and a significant anisotropy in tensile properties were recorded along the longitudinal and peripheral directions. The HTCEE process increased the yield strength and the ultimate strength in the axial direction by 3.6 and 1.67 times, respectively. Also, this process increased the yield strength and the ultimate strength in the peripheral direction by 1.15 and 1.12 times, respectively. The ratio of ultimate tensile strength in the peripheral direction to that in the axial direction, as a criterion for mechanical anisotropy, are 1.7 and 1.16 for the as-annealed coarse-grained and the HTCEE processed UFG tube, respectively. The results are indicative of a reducing effect of the HTCEE process on the mechanical anisotropy. Besides, after HTCEE process, a low loss of ductility was observed in both directions, which is another advantage of HTCEE process. Hardness measurements revealed a slight increment of hardness values in the peripheral direction, which is in agreement with the trend of tensile tests. Texture analysis was conducted in order to determine the oriental distribution of the grains. The obtained 111 pole figures demonstrate the texture evolution and reaffirm the anisotropy observed in mechanical properties. Scanning electron microscopy micrographs showed that different modes of fracture occurred after tensile testing in the two orthogonal directions.

 

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