Spatial orientations and structural irregularities associated with the formation of microbands in a cold deformed Goss oriented Ni single crystal

The crystallographic nature of microband boundaries was investigated in a Goss oriented nickel single crystal following cold deformation in channel die plane strain compression. Standard electron backscatter diffraction (EBSD), three-dimensional (3-D)-EBSD and transmission electron microscopy (TEM) were used in the investigation. When viewed in the three orthogonal sections microband boundary traces were classically aligned in the transverse direction section at an acute angle from the rolling direction (RD), but appeared wavy in the normal direction (ND) section. The latter observation may lead to the conclusion that microband boundaries are non-crystallographic. 3-D EBSD was used to reconstruct actual microbands in a deformed volume that revealed significant new information about their structure. Here microband surfaces are largely planar over large distances, but frequently interrupted by local distortions and undulations due to interactions between intersecting non-coplanar microbands. The combined EBSD/TEM investigation has revealed that microband boundaries are aligned close to an active {1 1 1} slip plane (i.e. they are crystallographic), but the undulations and distortions they contain are non-crystallographic in the sense that they deviate from an active slip plane. The non-crystallographic features of microbands (as revealed by their wavy structure in the ND section) may be explained by the crystallographic oscillations of up to ±7.5° towards RD that occur during plastic deformation. Such oscillations result in varying fractions of slip on a given {1 1 1} plane, resulting in varying degrees of interaction between the two sets of non-coplanar microbands. These local and intense microband interactions result in their deviation from their active slip planes.     

Theoretical analysis of texture evolution in cold rolling process of single crystal aluminum

The crystal plasticity finite element method（CPFEM）, which incorporates the crystal plasticity constitutive law into the finite element method, was developed to investigate the rolling processes of the cubic oriented and Goss oriented Al single crystal. The simulation results show that after rolling the crystal predominantly rotates around the transverse direction（TD） for both orientations. The rotations around the rolling direction（RD） and the normal direction（ND） are negligible. The reduction plays a significant role in the texture evolution. The TD rotation angle increases with increasing reduction. The deformation bands exist in the rolled specimens with the cubic initial orientation. Compared with the cubic oriented specimens, the TD rotation angles in the Goss oriented specimens are very small.     

冷轧变形对Al-Zn-Mg-Cu铝合金剥落腐蚀性能的影响

采用剥落腐蚀实验、电化学阻抗测试、透射显微技术等方法,研究了不同冷轧变形量对Al-Zn-Mg-Cu合金组织和剥落腐蚀性能的影响.结果表明:随着冷轧变形量的增加,合金在EXCO溶液中剥落腐蚀增大.变形量主要通过改变晶粒形态及晶界析出相影响合金的剥落腐蚀性能.一方面冷变形导致合金晶粒纵横比增大,使得腐蚀裂纹尖端处产生的楔入应力增加,裂纹扩展速率提高;另一方面,较大冷变形合金时效时形成的连续晶界析出相易成为阳极腐蚀通道,也会加速剥落腐蚀进程.     

螺旋选晶器对单晶高温合金晶粒取向的影响(英文)

对于航天推进和发电燃气轮机,为了实现更高的效率和性能并同时降低成本和排放,需要发展先进的镍基单晶高温合金。随着合金的发展,合金的铸造技术已经从定向凝固(DS)发展到单晶(SX)。单晶取向与择优取向的偏差已经成为单晶高温合金最重要的铸造缺陷之一。在自行设计的高温度梯度定向凝固装置中,采用改进的Bridgeman法,用螺旋选晶器拉制出DZ417G合金的单晶。使用XRD和EBSD对其取向进行分析研究。结果表明:较小角度的螺旋选晶器可以有效地减少单晶取向与择优取向的偏差。     

High orientation Al films growth on LiNbO3 single crystal and its adhesion

High orientation Al films were deposited on 64°Y-XLiNbO3 substrate by DC magnetron sputtering and the influence of deposition temperature on microstructure and adhesion properties of Al films were investigated. The results show that crystallographic orientation of films varies with substrate temperature and the adhesion strength between LiNbO3 and Al films strongly depends on crystallographic orientation of Al films. The (111) orientated Al films shows stronger adhesion strength to LiNbO3 substrate than (100) orientated films. There is an optimum substrate temperature of 60 ℃ and hardening temperature of 200 ℃ for obtaining high (111) orientated Al films with good surface structure and adhesion property. Using this Al film, we have successfully fabricated the SAW filters with high frequency of about 1.89 GHz.     

Microstructural changes of nanocrystalline nickel during cold rolling

The microstructural changes of electrodeposited nanocrystalline Ni with an initial grain size of about ∼30–40 nm during cold rolling up to 76% thickness reduction have been studied using X-ray diffraction and transmission electron microscopy. In response to the cold deformation processing we observed significant changes in the scale and morphology of grains, defect content, as well as of crystallographic texture. Our experimental findings for nanocrystalline Ni are directly compared to the behavior of coarse-grained Ni. The role of the grain scale reduction to the nanometer regime is discussed with respect to the microstructural changes.     

Effect of deformation inhomogeneities on the formation of texture during cold rolling and annealing of nickel single crystals

Structure and texture of rolled nickel single crystals of various initial orientations have been studied in some detail. Special attention has been paid to the specific features of the deformation mesostructure and the possibility of formation of nuclei of primary recrystallization of cube orientations in it.     

Influence of crystal orientation on cellular growth of a nickel-base single crystal superalloy

The cellular pattern evolution during directional solidification of a nickel-base single crystal superalloy has been studied in different crystallographic orientations using re-oriented seed crystals. Under the same thermal gradient and solidification velocity, the microstructures of differently oriented cellular single crystals are schematically investigated. It is concluded that the cellular growth direction is less affected by the seed orientation and depends on the heat flow, and is usually along heat flow direction. Cellular interface stability and microstructure are greatly influenced by the crystallographic orientation. When increasing the misorientation, the cell spacing increases correspondingly and the cellular growth interface becomes more unstable.     

Predictive modeling of grain refinement during multi-pass cold rolling

Recently, grain refinement and grain misorientation have been experimentally studied for various materials with ultra-fine grained microstructures, which are achieved by the multi-pass cold rolling process. In this paper, a numerical framework is developed to model the evolution of grain size and grain misorientation based on a dislocation density-based material model. Novel finite element models embedded with the dislocation density-based material subroutine are developed to model the plastic deformation and microstructural evolution during the multi-pass cold rolling process. The multi-pass cold rolling processes of commercially pure titanium (CP Ti) and aluminum (AA 1200) are simulated in order to assess the validity of the numerical solution through comparison with experiments. The dislocation density-based material models are developed for CP Ti and AA 1200, which reproduce the observed material constitutive mechanical behavior under various strains, strain rates and temperatures occurring in the cold rolling process. It is shown that the developed model captures the essential features of the material mechanical behaviors and predicts a minimum grain size of below 100 nm after five-pass cold rolling of CP Ti with equivalent strains up to 2.07 and the average incidental dislocation boundary (IDB) misorientation angle increased to 4.6° after six-pass cold rolling of AA 1200 with equivalent strains accumulated to 5.77.     

TiNbTaZr合金在轧制过程中的马氏体转变

利用真空自耗熔炼方法和热加工技术制备Ti-35Nb-2Ta-3Zr β钛合金,采用单向轧制和交叉轧制对合金进行冷变形.通过对轧制态试样的微观组织分析,研究不同轧制方式下的马氏体转变特征.结果表明:单向轧制和交叉轧制过程中产生应变诱发马氏体相,随着变形量的增大,马氏体形貌由针状逐渐转变为粗大的变体;交叉轧制更有利于马氏体相的转变,当冷变形量为40%时,马氏体的转变量达到79.63%,并在随后的冷变形过程中,马氏体转变量基本保持不变.     

Improving single pass reduction during cold rolling by controlling initial texture of AZ31 magnesium alloy sheet

The AZ31 magnesium alloy sheets obtained by multi-pass hot rolling were applied to cold rolling and the maximum single pass cold rolling reduction prior to failure of AZ31 magnesium alloy was enhanced to 41%. Larger single pass rolling reduction led to weaker texture during the multi-pass hot rolling procedure. The sheet obtained showed weak basal texture, while the value was only 1/3–1/2 that of general as-rolled AZ31 Mg alloy sheets. It was beneficial for the enhancement of further cold rolling formability despite of the coarser grain size. The deformation mechanism for the formation of texture in AZ31 magnesium alloy sheet was also analyzed in detail.     

冷轧板带变形的三维分析

应用三维弹塑性有限元法,在大型商业有限元软件平台上开发了冷轧板带模拟系统,分析了轧件变形情况,考虑了不同厚度,压下率和摩擦系数的影响,并计算了边降及金属向流动的变化规律,计算结果与实验结果吻合情况较好。     

单机架可逆冷轧过程中不同厚度规格低碳铝镇静钢的组织性能

采用铜丝定点标记法,研究了H-C单机架可逆冷轧低碳铝镇静钢过程中的变形规律,通过单向拉伸实验检测不同厚度规格钢板力学性能,利用光学显微镜观察实验钢板冷轧态及退火态的显微组织,并用电子背散射衍射仪(EBSD)测量了两种厚度实验钢板取向织构情况。结果表明,可逆冷轧过程中沿断面高度方向上各处金属质点流动速度相同,没有明显的剪切变形。试样压下率从34%升高到80%时,r值范围为1.13~1.36,n值范围为0.23~0.24。压下率从64%升高到80%时,退火试样再结晶组织中有利的111∥ND取向晶粒所占比例增加,对深冲性能有利。     

Strain distribution of strips with spherical inclusion during cold rolling

The deformation of 304 stainless steel strips with a spherical inclusion during cold rolling was simulated by 3D finite element method, and the strain distribution was calculated for a variety of the material attribution of inclusion （hard inclusions and soft inclusions） and the inclusion size （10, 20, 30, 40, and 50 μm）. During rolling, the strain in front of inclusion is larger than that in rear of inclusion for both the hard and soft inclusions. For hard inclusions, the strain in front and rear of inclusions is larger than that of inclusions, and the maximum and minimum strains increase with the increase of inclusion diameter （from 10 μm to 50 μm）. For soft inclusions, the strain in front and rear of inclusions is smaller than that of inclusions, and the maximum and minimum strains decrease with the increase of inclusion sizes when the inclusion diameter is larger than 20μm but increase when the inclusion diameter is smaller than 20 μm. Finally, the relationship between the inclusion deformation and the crack generation was discussed.     

铝板带冷轧过程中辊系变形的模拟计算

针对铝板带冷轧过程中弯辊力的预设定问题,采用非线性有限元仿真软件ABAQUS建立了辊系的三维弹塑性有限元模型和工作辊的热凸度模型,通过改变模型的边界条件进行有限元求解,分析了板带轧制过程中弯辊力变化对辊系的弹塑性变形影响以及工作辊的热变形特征,并将模拟结果与某厂生产现场采集的数据进行比较。结果表明弯辊力对板形对称缺陷的改善效果明显,并得出弯辊力的最佳设定值约为300 k N;分段冷却使工作辊热凸度减小了约25μm;二者配合使用使工作辊横向承载辊缝值分布趋于均匀,板带板形趋于良好。     

Effect of rolling parameters on cold rolling of thin strip during work roll edge contact

In some cold rolling mills, a problem has been found that the sides of work rolls touch and deform when thin strip is rolled. The problem of work roll contact at the edges, which forms a new deformation feature in rolling, is analysed. In this paper, the authors focus on the research of the effects of rolling parameters on specific force such as rolling force, intermediate force, edge contact force and the profile of thin strip in cold rolling when the work roll edges contact. An influence function method is developed to simulate this special rolling process. Based on numerical simulation, the effects of the rolling parameters on the mechanics and deformation of the cold rolled thin strip are obtained. Numerical simulation tests have verified the validity of this developed method.     

冷轧间热处理对Al-Mg-Si-Cu基合金板材轧制织构的影响

采用晶体取向分布函数(ODF)法研究了轧间热处理对Al-Mg-Si-Cu基合金板材轧制织构的影响.结果表明,轧间不热处理和350℃×1 h热处理,两种板材的织构类型基本一致,主要为R-Cube{001}<110(旋转立方织构)及强度较弱的B、S、C织构;而经510 ℃×1 h热处理的板材的R-Cube及B、S、C织构的强度都比前两种板材相应织构要低得多.没有热处理试样的{001}<110的含量为21.2%,取向密度值f(g)为18.1;经过350℃×1 h处理的试样的{001}<110的含量为19.8%,f(g)为16.8;经过510 ℃×1 h处理的试样的{001}<110的含量为13.7%,f(g)为3.2.     

Earing behavior and crystallographic texture of aluminum alloys during cold rolling

Earing behavior and crystallographic texture during cold rolling have been investigated for two commercial can body aluminum alloys. It is found that earing behavior can be inferred from texture information. The recrystallization texture causes 90° earing, while the deformation texture results in 45° earing. A strong recrystallization texture (or a high 90° earing) of a hot band causes a later appearance of lower 45° earing in the final gauge sheet and thus is desirable for industry. The earing behavior is better indicated by the delta function, which is characterized as the intensity difference between the deformation texture and the softening texture. The results indicate that the earing behavior during cold rolling can be quantitatively monitored by the crystallographic texture. In addition, effects of the texture inhomogeneity through-thickness have also been investigated and discussed.