电刷镀大块纳米铜的制备及压缩性能研究
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摘要
本文采用改进的电刷镀技术,制备了高纯度,具有真正纳米晶结构的均匀大块纳米铜样品,利用X-衍射分析、扫描电子显微镜、场发射扫描电子显微镜,透射电子显微镜的设备,对电刷镀纳米铜表面沉积形态、显微结构等进行相应的表征工作,结果显示,电刷镀纳米铜为等轴晶粒结构,平均晶粒尺寸为26nm,且尺寸分布均匀,主要为大角度晶界结构,不存在微观裂纹和微孔和明显的晶体织构,平方根微应变为0.28%。电刷镀纳米铜沉积表面光滑,粗糙度低,具有良好的覆盖性和平整性。利用压缩和压缩蠕变以及应变速率跳跃试验测定了电刷镀纳米铜的相关力学性能,重点研究了应变速率对压缩性能的影响,并对相关的塑性变形机制进行了分析。
The mechanical properties of nanocrystalline (nc) metals have been a main research topic in materials science communities, which involve quantificational descriptions of macro-mechanical behavior and qualitative analyses of micro-deformation mechanisms of nc metals. However, due to synthesis problems, bulk nc metals with high metallurgical qualities and truly nc structures cannot be prepared so far. This leads to considerable limits to substantial understanding of plastic deformation mechanisms of nc metals. On the other hands, it has been suggested that grain boundary (GB) process and dislocation activities are the two main mechanisms controlling mechanical properties of nc metals. It is a center problem of plastic deformation mechanism investigations to reveal the effects of both mechanical and thermal roles caused due to changes in grain size, temperature and stain rate.
Based on the above two points, the following research work was conducted in this doctoral dissertation and the resultant conclusions are presented as the following:
1. A new electrical brush-plating technique for synthesizing bulk nc-Cu with high metallurgical qualities and truly nc structure was developed. The stylus is made by a stainless steel (AISI304) wrapped by cotton and polypropylene fabric, the bath contents CuSO_4·5H_2O, NH_4NO_3, C_6H_8O_7·H_2O and a small amount of additives. During the brush-plating operation,[Cu(NH_3)_6]~(2+) complex ions are reduced under ultra-voltage into Cu deposition. The formation of nc-Cu deposition takes form of 2D nucleation and then 3D growth. The deposition structure of nc-Cu is affected by substrate surface state. A good substrate surface state can lead to a high quality of deposition structure. The use of additives can control the grain size of nc-Cu deposition and restrain the formations of crystallite clusters and coarser grains. The friction between stylus and substrate increases nucleation rate and has a cleanse role. By the appropriate controls of the parameters such as voltage, temperature, stylus velocity and bath flux, a bulk nc-Cu with high metallurgical quality can be obtained by the brush-plating technique.
2. Surface morphologies, microstructure, compositions, and density of the brush-plated nc-Cu were characterized by using XRD, SEM, FESEM, TEM, etc. It was demonstrated that the brush-plated nc-Cu has equiaxed grains separated by predominant high-angle GBs and no detectable porosities or voids with the mean grain size of about 26nm and the crystalline (root-mean-square) micro-strain of 0.28%. The brush-plated nc-Cu has a smooth deposition surface, a good coverage.
3. The room temperature compressive creep test revealed a Coble creep at lower stress level and the subsequent two power-law creeps with the stress exponents of n =1/m=4.41 and 11.24, respectively, with the latter being consistent with the m of the first stage of the compressive deformation. The three creeps do not show the presence of the threshold stress. The room temperature compressive test revealed also a pronounced strain rate sensitivity with an m=0.084 at low strain rates and an m=0.036 at high strain rates. respectively. The strain rate jump test revealed a decrease of m from 0.18 to 0.018 .In the strain rate tested, the strength at 2% plastic strain increases from 664MPa to 1516MPa, respectively, with the latter is the highest strength value of all Cu so far. At high strain rates, a strain rate-dependent flow softening was observed. The deformation mechanism analysis showed that the plastic deformation of the brush-plated nc-Cu is controlled by the dominant GB sliding at low strain rates and by the dominant dislocation activity at high strain rates. Such a transition in the deformation mechanism arises from the suppression of the strain rate on thermal activation role. The reduced contribution of the GB deformation and the increased contribution of the dislocation deformation lead to a large strength increment. The local adiabatic thermal softening role is responsible for the enhanced flow softening at high strain rates.
The mechanical properties of nanocrystalline (nc) metals have been a main research topic in materials science communities, which involve quantificational descriptions of macro-mechanical behavior and qualitative analyses of micro-deformation mechanisms of nc metals. However, due to synthesis problems, bulk nc metals with high metallurgical qualities and truly nc structures cannot be prepared so far. This leads to considerable limits to substantial understanding of plastic deformation mechanisms of nc metals. On the other hands, it has been suggested that grain boundary (GB) process and dislocation activities are the two main mechanisms controlling mechanical properties of nc metals. It is a center problem of plastic deformation mechanism investigations to reveal the effects of both mechanical and thermal roles caused due to changes in grain size, temperature and stain rate.
Based on the above two points, the following research work was conducted in this doctoral dissertation and the resultant conclusions are presented as the following:
1. A new electrical brush-plating technique for synthesizing bulk nc-Cu with high metallurgical qualities and truly nc structure was developed. The stylus is made by a stainless steel (AISI304) wrapped by cotton and polypropylene fabric, the bath contents CuSO_4·5H_2O, NH_4NO_3, C_6H_8O_7·H_2O and a small amount of additives. During the brush-plating operation,[Cu(NH_3)_6]~(2+) complex ions are reduced under ultra-voltage into Cu deposition. The formation of nc-Cu deposition takes form of 2D nucleation and then 3D growth. The deposition structure of nc-Cu is affected by substrate surface state. A good substrate surface state can lead to a high quality of deposition structure. The use of additives can control the grain size of nc-Cu deposition and restrain the formations of crystallite clusters and coarser grains. The friction between stylus and substrate increases nucleation rate and has a cleanse role. By the appropriate controls of the parameters such as voltage, temperature, stylus velocity and bath flux, a bulk nc-Cu with high metallurgical quality can be obtained by the brush-plating technique.
2. Surface morphologies, microstructure, compositions, and density of the brush-plated nc-Cu were characterized by using XRD, SEM, FESEM, TEM, etc. It was demonstrated that the brush-plated nc-Cu has equiaxed grains separated by predominant high-angle GBs and no detectable porosities or voids with the mean grain size of about 26nm and the crystalline (root-mean-square) micro-strain of 0.28%. The brush-plated nc-Cu has a smooth deposition surface, a good coverage.
3. The room temperature compressive creep test revealed a Coble creep at lower stress level and the subsequent two power-law creeps with the stress exponents of n =1/m=4.41 and 11.24, respectively, with the latter being consistent with the m of the first stage of the compressive deformation. The three creeps do not show the presence of the threshold stress. The room temperature compressive test revealed also a pronounced strain rate sensitivity with an m=0.084 at low strain rates and an m=0.036 at high strain rates. respectively. The strain rate jump test revealed a decrease of m from 0.18 to 0.018 .In the strain rate tested, the strength at 2% plastic strain increases from 664MPa to 1516MPa, respectively, with the latter is the highest strength value of all Cu so far. At high strain rates, a strain rate-dependent flow softening was observed. The deformation mechanism analysis showed that the plastic deformation of the brush-plated nc-Cu is controlled by the dominant GB sliding at low strain rates and by the dominant dislocation activity at high strain rates. Such a transition in the deformation mechanism arises from the suppression of the strain rate on thermal activation role. The reduced contribution of the GB deformation and the increased contribution of the dislocation deformation lead to a large strength increment. The local adiabatic thermal softening role is responsible for the enhanced flow softening at high strain rates.
引文
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[2] H. Gleiter. Nanostructured materials: basic concepts and microstructure. Acta Mater. 48, 1 (2000).
[3] H. Gleiter. Nanocrystalline materials. Prog. Mater. Sci. 33, 223 (1989).
[4] S. C. Tjong, and H. Chen. Nanocrystalline materials and coatings. Mater. Sci. Eng. R. 45, 1 (2004).
[5] 卢柯, 周飞. 纳米晶体材料的研究现状. 金属学报. 33 (1997).
[6] P. G. Sanders, G. E. Fougere, L. J. Thompson, and J. A. Eastman, J.R.Weertman. Improvements in the synthesis and compaction of nanocrystalline materials. Nanostructured. Mater. 8, 243 (1997).
[7] C. C. Koch. Synthesis of nanostructured materials by mechanical milling: problems and opportunities. Nanostr. Mater. 9, 13 (1997)。
[8] C. C. Koch. The synthesis and structure of nanocrystalline materials produced by mechanical attrition: a review. Nanostructured. Mater. 2(2), 109 (1993).
[9] G. Salishchev, R. Zaripova, R. Galeev, and O. Valiakhmetov. Nanocrystalline structure formation during severe plastic deformation in metals and their deformation behavior. Nanost. Mater. 6, 913 (1995).
[10] R. Z. Valiev, and R. K. Islamgaliev and I. V. Alexanderov. Bulk nanostructure materials from severe plastic deformation. Prog. Mater..Sci. 45, 103 (2000).
[11] V. V. Stolyarov, and R. Z. Valiev. Bulk nanostructured metastable alloys prepared by severe plastic deformation. Mater. Sci. Forum. 307, 185 (1999).
[12] U. Erb. Electrodeposited nanocrystals: Synthesis, properties and industrial application. Nanostructured. Mater. 6, 533 (1995).
[13] C. C. Koch. Optimization of strength and ductility in nanocrystalline and ultrafine grained metals. Scr. Mater. 49, 657 (2003).
[14] ]U. Erb, A. M. EI-Sheeik, G. Palumbo, and K. T. Aust. The synthesis, structure, and properties of electroplated nanocrystalline materials. Nanostr. Mater. 2(4), 383 (1993).
[15] Lu K. Nanocrystalline metals crystallized from amorphous solids: nanocrystallization, structure, and properties. Mater. Sci. Eng. R. 16, 161 (1996).
[16] 徐滨士主编. 表面工程与维修. 机械工业出版社. 342-362 (1996).
[17] J. C. Norris. Brush Plating. Metal Finishing, 93, 349 (1995).
[18] D. L. Vanek. Selective electrofinishing. Metal Finishing, 97, 361 (1999).
[19] 梁志杰、臧永华编著. 刷镀技术使用指南. 中国建筑工业出版社. 1 (1988).
[20] 方景礼、惠文化编. 刷镀技术.国防工业出版社. 58 (1990).
[21] B. Subramanian, C. Sanjeeviraja, and M. Jayachandran. Brush plating of tin(II) selenide thin films, J. Crys. Growth. 234, 421 (2002).
[22] B. Subramanian, C. Sanjeeviraja, and M. Jayachandran. Photoelectrochemical characteristics of brush plated tin sulfide thinfilms. Solar Energy Materials & Solar Cells, 79, 57 (2003).
[23] S. B. Hu, J. P. Tu, Z. Mei, Z. Z. Li, and X. B. Zhang. Adhesion strength and high temperature wear behaviour of ion plating TiN composite coating with electric brush plating Ni-W interlayer. Surf. Coat. Tech. 141, 174 (2001).
[24] W. Hui, J. Liu, Y. Chaug, and J. K. Dennis. A study of wear resistance of a new brush-plated alloy Ni-Fe-W-S. Wear, 192, 165 (1996).
[25] L. Du, B. Xu, S. Dong, H. Yang, and W. Tu. Study of tribological characteristics and wear mechanism of nano-particle strengthened nickel- based composite coatings under abrasive contaminant lubrication. Wear, 257, 1058 (2004).
[26] X. Jiang, X. Xie, and Z. Xu. Double glow surface alloying of low carbon steel with electric brush plating Ni interlayer for improvement in corrosion resistance. Surf. Coat. Tech. 168, 156 (2003).
[27] X. Jiang, X. Zhang, X. Xie, Z. Xu, and W. Liu. Ni-based superalloy surface alloying by double-glow plasma surface alloying technique. Vacuum, 72, 489 (2004).
[28] X. Liu, B. Xu, S. Ma, and Z. Chen. Study of the tribological behavior of a Ni electron brush plating layer on a base of an Arc sprayed coating. Wear, 211, 151 (1997).
[29] L. Du, B. Xu, S. Dong, H. Yang, and W. Tu. Study of tribological characteristics and wear mechanism of nano-particle strengthened nickel- based composite coatings under abrasive contaminant lubrication. Wear, 257, 1058 (2004).
[30] R. P. Yang, X. Cai, and Q. L. Chen. Mechanism of hydrogen desorptionduring palladium brush-plating. Surf. Coat. Tech. 141, 283 (2001).
[31] Y. M. Wang, K. Wang, D. Pan, K. Lu, K. J. Hemker, and E. Ma, Microsample tensile testing of nanocrystalline copper, Scr. Mater. 48 1581 (2003).
[32] K. M. Youssef, R. O. Scattergood, K. L. Murty, J. A. Horton, and C. C. Koch, Ultrahigh strength and high ductility of bulk nanocrystalline copper, Appl. Phys. Lett. 87, 091904 (2005).
[33] S. Cheng, E. Ma, Y. M. Wang, L. J. Kecskes, K. M. Youssef, C. C. Koch, U. P. Trociewitz, and K. Han. Tensile properties of in situ consolidated nanocrystalline Cu. Mechanistic models for the activation volume and rate sensitivity in metals with nanocrystalline grains and nano-cale twins. Acta Mater. 53, 1521 (2005).
[34] L. Lu, M. L. Sui, and K. Lu. Superplastic extensibility of nanocrystalline copper at room temperature. Science, 287, 1463-1466 (2000).
[35] B. Cai, Q. P. Kong, L. Lu, and K. Lu. Interfce controlled diffusional creep of nanocrystalline pure copper. Scripta Materialia, 41, 755-759 (1999).
[36] T. F. Dalla, H. Van Swygenhoven, and M. Victoria. Nanocrystalline electrodeposited Ni: microstructure and tensile properties. Acta Materialia, 50, 3957-3970 (2002).
[37] C. J. Youngdahl, P. G. Sanders. J. A. Eastman, and J. R. Weertman, Compressive yield strengths of nanocrystalline Cu and Pd, Scr. Mater. 37, 809 (1997).
[38] D. Jia, K. T. Ramesh, E. Ma, L.Lu, and K. Lu, Compressive behavior ofan electrodeposited nanostructured copper at quasistatic and high strain rates, Scr. Mater. 45, 613 (2006).
[39] Y. M. Wang, and E. Ma, Temperature and strain rate effects on the strength and ductility of nanostructured copper, Appl. Phys. Lett., 83, 3165 (2003).
[40] Q. Wei, S. Scheng, K. T. Ramesh, and E. Ma, Effect of nanocrystalline and ultrafine grain sizes on the strain rate sensitivity and activation volume: fcc versus bcc metals, Mater. Sci. Eng. A381, 71 (2004).
[41] S. Cheng, E. Ma, Y. M. Wang, L. J. Kecskes, K. M. Youssef, C. C. Koch, U. P. Trociewitz, and K. Han, Tensile properties of in situ consolidated nanocrystalline Cu, Acta Mater. 53, 1521 (2005).
[42] Y. M. Wang, and E. Ma, Strain hardening, strain rate sensitivity, and ductility of nanostructured metals, Mater. Sci. Eng. A375-377, 46 (2004).
[43] R. Schwaiger, B. Moser, M. Dao, N. Chollacoop, and S. Suresh, Some critical experiments on the strain-rate sensitivity of nanocrystalline nickel, Acta Mater. 51, 5159 (2003).
[44] L. Lu, R. Schwaiger, Z. W. Shan, M. Dao, K. Lu, and S. Suresh, Nano-sized twins induce high rate sensitivity of ?ow stress in pure copper, Acta Mater. 53, 2169 (2005).
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