Tensile strength and ductility of ultra-fine-grained nickel processed by severe plastic deformation
Tensile strength and ductility of ultra-fine-grained nickel processed by severe plastic deformation
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DOI：
10.1016/j.msea.2005.03.001
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发表时间：
2005-04-25
期刊：
影响因子：
6.4
通讯作者：
Valiev, R
中科院分区：
文献类型：
--
作者：
Krasilnikov, N;Lojkowski, W;Valiev, R
研究了通过等通道角挤压（ECAP）和冷轧或高压扭转进行严重塑性变形的镍的结构和机械性能。获得的材料具有均匀的超细晶粒 (UFG) 微观结构，平均晶粒尺寸在 100 至 600 微米之间，具体取决于加工程序。室温拉伸测试显示，极限拉伸强度值在 840 至 1270 MPa 范围内，断裂伸长率在 7% 至 12% 范围内，具体取决于加工方法。通过 ECAP 和冷轧变形的样品在 200 摄氏度下退火，从而获得强度和塑性的最佳组合。该材料的强度远高于霍尔-佩奇规则的预期水平。我们通过考虑晶界 (TLD) 处的位错来解释这种高强度。在超细晶粒 (LJFG) 材料中，晶界比表面较高，因此 TLD 密度也较高。断裂和变形释放表明晶界滑动和晶粒旋转作为变形机制的重要作用。 UFG 高强度镍具有相对良好的延展性，特别是在微系统中具有应用潜力，其中材料的横截面在微米范围内，但仍必须穿过足够数量的晶粒才能看起来结构均匀。 (c) 2005 年 Elsevier B.V. 出版
The structure and mechanical properties of Ni subjected to severe plastic deformation by means of equal channel angular pressing (ECAP) followed by cold rolling or high-pressure torsion were investigated. A material with uniform ultra-fine-grained (UFG) microstructure and mean grain size in the range from 100 to 600 urn, depending on the processing procedure, was obtained. Tensile tests at room temperature revealed ultimate tensile strength values in the range from 840 to 1270 MPa and an elongation to fracture in the range from 7 to 12% depending on the processing method. Annealing at 200 degrees C of the sample deformed by ECAP and cold rolling led to the best combination of strength and plasticity. The strength of the material was well above the level expected from the Hall-Petch rule. We explained this high strength by taking into account dislocations trapped at grain boundaries (TLDs). In ultra-fine-grained (LJFG) materials the specific surface of grain boundaries is high and therefore the TLDs density is high as well. The fracture and deformation relief indicate an important role of grain-boundary sliding and grain rotation as deformation mechanisms. The UFG high-strength Ni with relatively good ductility has a potential for applications in particular in microsystems, where the cross section of the material is in the micrometer range but still must cross a sufficient number of grains to look structurally uniform. (c) 2005 Published by Elsevier B.V.