晶粒取向和晶界对双晶铜变形的影响
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摘要
在扫描电子显微镜(SEM)下拉伸双晶铜样品,用数字图像相关方法(DIC)处理样品在不同应变状态下的SEM图片,得到正应变场E_(xx)和剪应变场E_(xy),并通过E_(xx)和E_(xy)的演化研究双晶铜的变形特征,以及晶粒取向和晶界对它的影响。正应变场E_(xx)显示两晶粒内部、晶界附近分别有单、双系滑移开启,滑移带会造成局部变形的不均匀。随着应变的增加,滑移带数量增多而强度减小,变形趋于均匀化。相比软取向晶粒,硬取向晶粒中的滑移带数量少而滑移带强度高。剪应变场E_(xy)幅值远小于E_(xx)幅值,因而观察不到滑移带。软取向晶粒比硬取向晶粒的平均正应变E_(xx)大,它们之间的差别在8%的拉伸应变后随着应变的增加而被放大,晶界产生更高的协调应力,使得晶界附近的剪应变E_(xy)开始急剧增加。
Bicrystal copper sample is stretched under scanning electron microscope(SEM). SEM sample pictures obtained under different strain states are processed by digital image correlation(DIC) method. The normal strain field E_(xx) and shear strain field E_(xy) are obtained. The deformation characteristics and influence of grain orientation and grain boundary(GB) on deformation of bicrystal copper are studied based on E_(xx) and E_(xy) evolution. Normal strain field E_(xx) reveals that the single and double slip systems are activated at two grain interiors and GB vicinity, respectively. Slip band may result in unhomogeneity of local deformation. With the increase of strain, the number of slip band increases, but the strength decreases and the deformation tends to homogenous. Compared with soft-oriented grains, there are fewer slip bands and higher strength of slip bands in hard-oriented grains. The amplitude of shear strain E_(xy) is much smaller than that of normal E_(xx), so the slip bands can′t be observed in shear strain field E_(xy). The average normal strain(E_(xx)) of soft orientation grain is larger than that of hard orientation grain. The difference between them is amplified with the increase of strain after reaching 8% tensile strain. Higher coordinated stress at grain boundaries leads to a sharp increase in shear strain E_(xy) near grain boundaries.
Bicrystal copper sample is stretched under scanning electron microscope(SEM). SEM sample pictures obtained under different strain states are processed by digital image correlation(DIC) method. The normal strain field E_(xx) and shear strain field E_(xy) are obtained. The deformation characteristics and influence of grain orientation and grain boundary(GB) on deformation of bicrystal copper are studied based on E_(xx) and E_(xy) evolution. Normal strain field E_(xx) reveals that the single and double slip systems are activated at two grain interiors and GB vicinity, respectively. Slip band may result in unhomogeneity of local deformation. With the increase of strain, the number of slip band increases, but the strength decreases and the deformation tends to homogenous. Compared with soft-oriented grains, there are fewer slip bands and higher strength of slip bands in hard-oriented grains. The amplitude of shear strain E_(xy) is much smaller than that of normal E_(xx), so the slip bands can′t be observed in shear strain field E_(xy). The average normal strain(E_(xx)) of soft orientation grain is larger than that of hard orientation grain. The difference between them is amplified with the increase of strain after reaching 8% tensile strain. Higher coordinated stress at grain boundaries leads to a sharp increase in shear strain E_(xy) near grain boundaries.
引文
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[17] Chen P,Mao S C,Liu Y,et al.In-situ EBSD study of the active slip systems and lattice rotation behavior of surface grains in aluminum alloy during tensile deformation[J].Materials Science and Engineering:A,2013,580:114-124.
[18] Lu L,Bie B X,Li Q H,et al.Multiscale measurements on temperature-dependent deformation of a textured magnesium alloy with synchrotron X-ray imaging and diffraction[J].Acta Materialia,2017,132:389-394.
[2] 冯端.金属物理学(第一卷)[M].北京:科学出版社,1987:318-415 (FENG Duan.The physics of metals(1st vol)[M].Beijing:Science Press,1987:318-415 (in Chinese))
[3] Wieczorek N,Laplanche G,Heyer J K,et al.Assessment of strain hardening in copper single crystals using in situ SEM microshear experiments[J].Acta Materialia,2016,113:320-334.
[4] Kramer D E,Savage M F,Levine L E.AFM observations of slip band development in Al single crystals[J].Acta Materialia,2005,53(17):4655-4664.
[5] Kashihara K,Inoko F.Effect of piled-up dislocations on strain induced boundary migration (SIBM) in deformed aluminum bicrystals with originally ∑3 twin boundary[J].Acta Materialia,2001,49(15):3051-3061.
[6] Zhang Z F,Wang Z G.Cyclic deformation behaviour of a copper bicrystal with common primary slip planes[J].Philosophical Magazine A,2001,81(2):399-415.
[7] Zhang Z F,Wang Z G,Eckert J.What types of grain boundaries can be passed through by persistent slip bands?[J].Journal of Materials Research,2003,18(5):1031-1034.
[8] Rey C,Zaoui A.Slip heterogeneities in deformed aluminium bicrystals[J].Acta Metallurgica,1980,28(6):687-697.
[9] 范亚夫,魏延鹏,薛跃军,等.数字图像相关测试技术在霍普金森杆加载实验中的应用[J].实验力学,2015,30(5):590-598 (FAN Yafu,WEI Yanpeng,XUE Yuejun,et al.On the application of digital image correlation testing technology in hopkinson bar loading[J].Journal of Experimental Mechanics,2015,30(5):590-598 (in Chinese))
[10] 房亮,唐兆琛,杨福俊,等.数字图像相关方法在闭孔泡沫铝压缩试验中的应用[J].实验力学,2008,23(2):162-168 (FANG Liang,TANG Zhaochen,YANG Fujun,et al.Compressive test of closed-cell aluminum foam based on digital image correlation method[J].Journal of Experimental Mechanics,2008,23(2):162-168 (in Chinese))
[11] 潘兵,吴大方,夏勇.数字图像相关方法中散斑图的质量评价研究[J].实验力学,2010,25(2):120-129 (PAN Bing,WU Dafang,XIA Yong.Study of speckle pattern quality assessment used in digital image correlation[J].Journal of Experimental Mechanics,2010,25(2):120-129 (in Chinese))
[12] 刘颢文,张青川,于少娟,等.数字散斑法在局域剪切带三维变形研究中的应用[J].光学学报,2007,27(5):898-902 (LIU Haowen,ZHANG Qingchuan,YU Shaojuan,et al.Investigation on the three-dimensional of local shearing band by digital speckle metrology technique[J].Acta Optica Sinica,2007,27(5):898-902 (in Chinese))
[13] 章超,徐松林,王鹏飞.基于数字图像相关方法对冲击载荷下泡沫铝全场变形过程的测试[J].实验力学,2013,28(5):629-634 (ZHANG Chao,XU Songlin,WANG Pengfei.Test of aluminum foam deforming process under impact load based on digital image correlation method[J].Journal of Experimental Mechanics,2013,28(5):629-634 (in Chinese))
[14] Guo Y Z,Li F D,Suo T,et al.A close observation on the deformation behavior of bicrystal copper under tensile loading[J].Mechanics of Materials,2013,62:80-89.
[15] Chen C R,Li S X,Wang Z G.Characteristics of strain and resolved shear stress in a bicrystal with the grain boundary perpendicular to the tensile axis[J].Materials Science and Engineering:A,1998,247(1):15-22.
[16] Stinville J C,Vanderesse N,Bridier F,et al.High resolution mapping of strain localization near twin boundaries in a nickel-based superalloy[J].Acta Materialia,2015,98:29-42.
[17] Chen P,Mao S C,Liu Y,et al.In-situ EBSD study of the active slip systems and lattice rotation behavior of surface grains in aluminum alloy during tensile deformation[J].Materials Science and Engineering:A,2013,580:114-124.
[18] Lu L,Bie B X,Li Q H,et al.Multiscale measurements on temperature-dependent deformation of a textured magnesium alloy with synchrotron X-ray imaging and diffraction[J].Acta Materialia,2017,132:389-394.