第3期 张含卓等:应变速率对电沉积纳米晶铜拉伸性能的影响 .271. 形量的增大,纳米晶铜的(200)晶面织构逐渐消 nanocrystalline materials.Prog Mater Sci,2006,51:427 失,原因在于材料内部的晶粒或晶粒团簇发生转 [2]Van Swygenhoven H.Weertman J R.Deformation in nanocrys- 动3].图6(b)则表明,试样断口处的位错密度是未 talline metals.Mater Today,2006,9:24 [3]Lu L.Schwaiger R.Shan Z W.et al.Nano-sized twins induce 变形区位错密度的11倍左右,位错密度的增大有 high rate sensitivity of flow stress in pure copper.Acta Mater, 助于提高纳米晶铜抵抗塑性变形的能力,而发生在 2004,53:2169 断口处可使纳米晶铜在失稳阶段有较大的应变量, [4]Lu L.Sui M L.Lu K.Superplastic extensibility of nanocrys 这与拉伸曲线的结果一致,实验也对=1.04× talline copper at room temperature.Science.2000,287:1463 10-5s时的变形后试样进行了检测,发现此时试 [5]Wang Y M,Ma E.Three strategies to achieve uniform tensile deformation in a nanostructured metal.Acta Mater.2004.52; 样断口处的位错密度仅为未变形区位错密度的4倍 1699 左右,而(111)晶面与(200)晶面的衍射强度比基本 [6]Cheng JS.Chen H B.Cui H.et al.Nanocrystalline Al-Zn-Mg 不变 Cu alloy prepared by eryomilling.J Univ Sci Technol Beijing. 2006,28(7):654 3结论 (程军胜,陈汉宾,崔华,等.低温球磨制备纳米晶A一Z一Mg ℃u合金.北京科技大学学报,2006,28(7):654) 实验制备的纳米晶铜平均晶粒尺寸为56nm, [7]Wang N.Wang Z,Aust K T,et al.Room temperature creep be- 其晶粒尺寸分布较宽,有少量晶粒团簇和孪晶,室 havior of nanocrystalline nickel produced by an electrodeposition 温拉伸实验发现,纳米晶铜的屈服强度约为粗晶铜 technique.Mater Sci Eng.1997,A237:150 的3倍,而韧性与粗晶铜相近,随着应变速率的升 [8]Karimpoor AA.Erb U,Aust K T.et al.High strength 高,纳米晶铜的强度和韧性同时增大,而且韧性的速 nanocrystalline cobalt with high tensile ductility.Scripta Mater 2003,49:651 率敏感十分显著,升高应变速率,纳米晶铜的应变 [9]Lu L,Li SX,Lu K.An abnormal strain rate effect on tensile be- 硬化指数和硬化系数都增大,说明其应变硬化程度 havior in nanocrystalline copper.Scripta Mater,2001.45:1163 增加,使均匀塑性变形阶段的应变也随之增加·另 [10]Wu S D.Wang Z G.Jiang C B.et al.Shear bands in eyclically 一方面,失稳阶段的应变也随着应变速率的升高而 deformed ultrafine grained copper processed by ECAP.Mater 增大,表面形貌分析表明:低应变速率下,试样表面 Sei Eng,2004,A387/389:560 有剪切带和微裂纹生成,说明纳米晶铜由于局部应 [11]Qin X Y.Zhu X G.Gao S,et al.Compression behaviour of bulk nanocrystalline Ni-Fe.J Phys Condens Matter.2002.14: 力集中而导致断裂;而在高应变速率下,试样颈缩时 2605 有晶粒或晶粒团簇的转动发生,通过协调机制避免 [12]Mukherjee A K.An examination of the constitutive equation for 了局部应力集中,从而使颈缩变形充分发展 elevated temperature plasticity.Mater Sci Eng.2002.A322:1 [13]Gu C.Lian J.Jiang Z,et al.Enhanced tensile ductility in an 参考文献 electrodeposited nanocrystalline Ni.Scripta Mater.2006.54: 579 [1]Meyers M A.Mishra A.Benson DJ.Mechanical properties of形量的增大纳米晶铜的(200) 晶面织构逐渐消 失原因在于材料内部的晶粒或晶粒团簇发生转 动[13].图6(b)则表明试样断口处的位错密度是未 变形区位错密度的11倍左右.位错密度的增大有 助于提高纳米晶铜抵抗塑性变形的能力而发生在 断口处可使纳米晶铜在失稳阶段有较大的应变量 这与拉伸曲线的结果一致.实验也对 ε ·=1∙04× 10-5s -1时的变形后试样进行了检测发现此时试 样断口处的位错密度仅为未变形区位错密度的4倍 左右而(111)晶面与(200)晶面的衍射强度比基本 不变. 3 结论 实验制备的纳米晶铜平均晶粒尺寸为56nm 其晶粒尺寸分布较宽有少量晶粒团簇和孪晶.室 温拉伸实验发现纳米晶铜的屈服强度约为粗晶铜 的3倍而韧性与粗晶铜相近.随着应变速率的升 高纳米晶铜的强度和韧性同时增大而且韧性的速 率敏感十分显著.升高应变速率纳米晶铜的应变 硬化指数和硬化系数都增大说明其应变硬化程度 增加使均匀塑性变形阶段的应变也随之增加.另 一方面失稳阶段的应变也随着应变速率的升高而 增大.表面形貌分析表明:低应变速率下试样表面 有剪切带和微裂纹生成说明纳米晶铜由于局部应 力集中而导致断裂;而在高应变速率下试样颈缩时 有晶粒或晶粒团簇的转动发生通过协调机制避免 了局部应力集中从而使颈缩变形充分发展. 参 考 文 献 [1] Meyers M AMishra ABenson D J.Mechanical properties of nanocrystalline materials.Prog Mater Sci200651:427 [2] Van Swygenhoven HWeertman J R.Deformation in nanocrystalline metals.Mater Today20069:24 [3] Lu LSchwaiger RShan Z Wet al.Nano-sized twins induce high rate sensitivity of flow stress in pure copper.Acta Mater 200453:2169 [4] Lu LSui M LLu K.Superplastic extensibility of nanocrystalline copper at room temperature.Science2000287:1463 [5] Wang Y MMa E.Three strategies to achieve uniform tensile deformation in a nanostructured metal.Acta Mater200452: 1699 [6] Cheng J SChen H BCui Het al.Nanocrystalline A-l Zn-MgCu alloy prepared by cryomilling.J Univ Sci Technol Beijing 200628(7):654 (程军胜陈汉宾崔华等.低温球磨制备纳米晶 Al-Zn-Mg -Cu 合金.北京科技大学学报200628(7):654) [7] Wang NWang ZAust K Tet al.Room temperature creep behavior of nanocrystalline nickel produced by an electrodeposition technique.Mater Sci Eng1997A237:150 [8] Karimpoor A AErb UAust K Tet al. High strength nanocrystalline cobalt with high tensile ductility.Scripta Mater 200349:651 [9] Lu LLi SXLu K.An abnormal strain rate effect on tensile behavior in nanocrystalline copper.Scripta Mater200145:1163 [10] Wu S DWang Z GJiang C Bet al.Shear bands in cyclically deformed ultrafine grained copper processed by ECAP. Mater Sci Eng2004A387/389:560 [11] Qin X YZhu X GGao Set al.Compression behaviour of bulk nanocrystalline N-i Fe.J Phys Condens Matter200214: 2605 [12] Mukherjee A K.An examination of the constitutive equation for elevated temperature plasticity.Mater Sci Eng2002A322:1 [13] Gu CLian JJiang Zet al.Enhanced tensile ductility in an electrodeposited nanocrystalline Ni.Scripta Mater200654: 579 第3期 张含卓等: 应变速率对电沉积纳米晶铜拉伸性能的影响 ·271·