液氮动态塑性变形纯铜的定量化结构研究

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	液氮动态塑性变形纯铜的定量化结构研究
	严锋
学位类型	硕士
导师	卢柯 ; 陶乃镕
	2011
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	低温动态塑性变形定量结构表征背散射电子衍射会聚束电子衍射铜
摘要	"本研究选择具有中等层错能的面心立方纯铜为研究对象，用动态塑性变形技术在液氮温度下变形（LNT-DPD Cu），并利用先进的定量化结构表征手段—基于扫描电子显微镜的背散射电子衍射（EBSD）和基于透射电子显微镜的会聚束电子衍射（CBED）测量结构参数，根据不同变形结构对强度和储存能的贡献建立结构参数-强度、结构参数-储存能的定量关系。主要结论如下：（1） LNT-DPD Cu的变形结构不均匀，由位错滑移区（DS-region）、纳米孪晶区（NT-region）和剪切带区（SB-region）组成。LNT-DPD Cu是以<110>//LD （loading direction）和<111>//LD为主的丝织构，但 <110>丝织构强于<111>丝织构。（2） DS-region和SB-region的主要微观结构由延展位错界及其间的连接界面和孤立位错组成。与传统严重塑性变形相比，LNT-DPD Cu中DS-region具有：i) 更小的界面间距（121 nm），ii) 更高的位错密度（5.6×1015 m-2）， iii) 更低的大角晶界比例（~0）和iv) 更小的平均界面取向差（3.8°）。SB-region主要由小角晶界组成，界面间距小于50 nm，位错密度为1.7×1016/m2。（4）NT-region的变形孪晶界的取向差偏离标准的Σ3关系（60°/<111>），最大偏离角达9°。根据界面参数，计算变形孪晶界上的Frank位错密度为：1.7×1016/m2。（5）LNT-DPD Cu的强度是DS-region，NT-region和SB-region的强化贡献的线性叠加，强度贡献来源于位错强化（小角度位错界和晶内位错）和界面强化（大角晶界和变形孪晶界）。计算所得的结果（640 MPa）与试验值（620 MPa）吻合得很好。（6） LNT-DPD Cu的储存能可以由DS-region，NT-region和SB-region的贡献进行线性叠加来估算。位错区的储存能约为0.6 J/m2,孪晶区的储存能约为2.15 J/m2，剪切带区的储存能约为1.64 J/m2。样品总的储存能为1.73 J/g，与通过DSC测量得到的结果1.7 J/g吻合得很好。"
其他摘要	"A polycrystalline pure Cu (99.995%) has been subjected to dynamic plastic deformation a liquid nitrogen temperature (LNT-DPD Cu) to a strain of 2.1. The microstructures of LNT-DPD Cu has been observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the quantitative information was obtained by means of electron back-scatter diffraction (EBSD) and convergent beam electron diffraction (CBED). Based on the quantitative structural characterizations, the structural characteristics of LNT-DPD Cu compared with other SPD treated Cu have been highlighted, and the quantitative relationship between structural parameters-stress, structural parameters-stored energy have been established. The main results are as follows: 1. The microstructures of LNT-DPD Cu are inhomogeneous, composed of dislocation slip region (DS-region), nanoscale twinning region (NT-region) and shear banding region (SB-region). Two types of fiber textures have been confirmed, being <110> fiber and <111> fiber with the <110> fiber stronger than the <111> fiber. 2. The microstructures of the DS-region and SB-region are characterized by extended boundaries, interconnecting dislocation boundaries and isolated dislocations in the volume between the boundaries. The microstructures of DS-region in the LNT-DPD Cu show i) a smaller boundary spacing (121 nm); ii) a lower misorientation angle (3.8o), iii) a lower fraction of high angle boundaries (~0) and iv) a higher dislocation density (5.6×1015 m-2) compared with other SPD treated counterpart at low strain rate and room temperature. The boundaries in the SB-region are mainly low angle dislocation boundaries that are spaced <50 nm. The dislocation density was estimated to be 1.6×1016 m-2. 3. The boundaries in the NT-region are deviated from the perfect Σ3 relationship (60°/<111>) up to a maximum value of 9o. Based on the boundary parameters and the deviation angles, the density of Frank dislocation in the twin boundaries was estimated to be 1.7×1016/m2. 4. The flow stress-structural parameters relationship has been established based on the linear additivity of the weighted contributions from three types of microstructures in the LNT-DPD Cu sample, assuming dislocation strengthening from low angle dislocation boundaries and isolated dislocations and grain boundary strengthening from high angle boundaries.. The calculated stress (640 MPa) agrees well with the tensile testing (620 MPa). 5. Based on the structural parameter of LNT-DPD Cu, the stored energy of DS-region，NT-region and SB-region is approximately 0.6 J/m2, 2.15 J/m2 and 1.64 J/m2, respectively. The total stored energy of LNT-DPD Cu is estimated to be 1.73 J/g, which is very close to the DSC measurement."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64399
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	严锋. 液氮动态塑性变形纯铜的定量化结构研究[D]. 北京. 中国科学院金属研究所,2011.