Influence of crystal orientation on ECAP of aluminum single crystals

A single crystal of high purity aluminum, oriented with the {1 1 1} slip plane and the 1 1 0 slip direction rotated by 20° in a clockwise sense from the theoretical shear plane and the shear direction, was processed by equal-channel angular pressing (ECAP) through a single pass. This configuration was designated the 20° orientation and the results are compared with earlier data obtained on a similar high purity aluminum single crystal in the 0° orientation with the (1 1 1) slip plane and the 1 1 0 slip direction lying parallel to the shear plane and the shear direction. The results show that in both orientations the long axes of the subgrains lie parallel to the slip traces of the primary slip system and the average subgrain widths are 1.3 μm. However, the shearing characteristics are different because the 0° specimen exhibited a conventional B-type rolling texture whereas the 20° specimen deformed by slip on the primary slip system and this system rotated by 40° in a counter-clockwise sense as the specimen passed through the shear zone of the ECAP die.     

Texture comparison of an ordinary IF steel and a high-strength IF steel under ferritic rolling and high-temperature coiling

The present work was performed to investigate the texture difference of an ordinary Ti-IF steel and a high-strength Ti-IF steel under ferritic hot rolling and high-temperature coiling. Comparing with the completely recrystallized textures of the ordinary IF steel, the textures of the high-strength IF steel were still deformed textures. The texture difference for the two steels is related to high P content in the high-strength IF steel which prevents the recrystallization during the coiling process. For the ordinary IF steel, the texture components were mainly very weak {001}110 orientation at the surface, and partial 110//RD (rolling direction) textures focused on {223}110 orientation and 111/ND (normal direction) texture at the mid-section and 1/4-section. For the high-strength IF steel, the texture components were mainly of {110}001 orientation at the surface and of a sharp 110//RD texture from {001}110 to {223}110 and weak 111/ND texture at the mid-section and 1/4-section.     

3%Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律

利用电子背散射衍射(EBSD)技术和X射线衍射仪(XRD)研究3%(质量分数)Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律。结果表明:柱状晶长轴分别沿轧向、横向和法向放置,具有不同的初始织构。热轧后,表层形成的3种剪切取向中高斯取向较容易形成。中心区,RD样品中的α和γ线轧制取向,TD样品中的强γ线取向,ND样品中的强{100}取向以及各样品中的立方取向,均表现出明显的初始取向依赖性。冷轧后,RD,TD样品中的强{111}〈112〉取向来自热轧板中的高斯取向,ND样品中的强旋转立方取向遗传自初始{100}取向。受初始取向偏差及大晶粒尺寸影响,ND样品中的旋转立方取向晶粒内取向梯度较大。退火后,样品中心大尺寸的{100}取向晶粒是柱状晶初始取向遗传性的表现。     

Effect of substrate temperature on the texture and structure of polycrystalline Si0.7Ge0.3 films deposited on SiO2 by molecular beam deposition

The evolution of microstructure and texture of molecular beam deposited Si_0.7Ge_0.3 films on SiO₂ at the deposition temperature range of 400–700°C was investigated by X-ray diffraction and transmission electron microscopy. At deposition temperatures between 400 and below 500°C, the films were directly deposited as a mixed-phase on SiO₂ and have a inversely cone-shaped structure. In this temperature range deposited as a mixed-phase, the grain size increases as the temperature increases, so that the grains not only grow up by deposition, but also laterally grow by the solid phase crystallization, furthermore, the texture is changed from a {110} texture to mixed {311} and {110} textures. At 500°C, the film was deposited as only a crystalline phase and has a columnar structure with a strong {110} texture. In the temperature range of 500–700°C, as the temperature increases, the {311} and {111} textures develop whereas the {110} texture reduces. The film deposited at 700°C has a random orientation and structure.     

A study of recrystallisation textures in hot band of a continuous cast Al–Mn–Mg alloy

Abstract

The hot band of a commercial continuous cast (CC) Al–Mg–Mn alloy was annealed at different temperatures ranging from room temperature to 510°C for 3 h. The evolution of microstructure and crystallographic texture was investigated during the annealing treatment. It was found that the recrystallised alloy exhibited a severely elongated grain structure and a texture that consisted of a new type of component ({113}〈110〉) and two fibre components (〈100〉//ND and 〈110〉//ND), the axes of which were along the normal direction of the rolling plane (ND) in 〈100〉 and 〈110〉 respectively. The 〈100〉//ND fibre was dominated by a ND rotated cube orientation {001}〈310〉, while the 〈110〉//ND fibre was mainly composed of Goss and P orientation ({011}〈566〉). The formation of the {113}〈110〉 texture and two fibre textures was likely to be attributed to the concurrent precipitation effect taking place upon heating in annealing treatment of the alloy.     

Investigations of MX and γ′/γ″ precipitates in the nickel-based superalloy 718 produced by electron beam melting

Samples with a composition similar to the nickel-based superalloy Inconel alloy 718 were produced by electron beam melting of prealloyed powder and investigated with respect to type and composition of the strengthening precipitates. The matrix consists of γ grains orientated in nearly the same direction, almost like a single crystal. Coarse precipitates (<2 μm), mostly of the (Ti,Nb)(C,N,B) type with B1 structure, are aligned along the growth direction. TEM and APFIM investigations of the γ matrix revealed very fine γ″ precipitates of around 5–10 nm in size. Additionally, at small angle grain boundaries, coarser γ″ precipitates of 50–100 nm in size have been observed. The 0 01 γ//0 0 1 γ″ and {1 0 0} γ//{1 0 0} γ″ orientation relationship between γ and γ″, known from literature [M. Sundararaman, P. Mukhopadhyay, Mater. Charact. 31 (1993) 191–196], was confirmed. Some γ′ precipitates of 2–5 nm in size were observed by means of FIM.     

A study of precipitation and recrystallization behaviour of aluminium alloy AA1235

The recrystallization behaviour of 92% cold rolled commercial pure aluminium has been studied. Annealing was done at different conditions to evaluate the effect of recrystallization temperature and time on the microstructure and texture of the alloy along with a study of subsequent precipitation. Variation of orientation between grains has been studied by the orientation imaging microscopy (OIM). During precipitation, cube component {001}<100> has dropped and rolling texture component has increased comparatively. Recrystallization texture is the combination of cube, rolling and random texture. However, during grain growth strong cube grains have formed. A significant number of dislocations are present during grain growth owing to the pinning effect of Al₃Fe particles.     

Evolution of texture at the initial stages of continuous annealing of cold rolled dual-phase steel: Effect of heating rate

The performance of cold rolled dual-phase (DP) steels depends on their microstructure, which results from the thermomechanical processing conditions, involving hot rolling, cold rolling and continuous annealing. In the present work, the effects of intercritical annealing parameters i.e. heating rate, soaking temperature and time and the cooling rate on the texture and microstructure of a cold rolled DP steel (0.08%C–1.91%Mn) were investigated after simulating through Gleeble thermomechanical simulator. The soaking temperature was chosen in a way that all the ferrite has recrystallized before the temperature was reached. The three different heating rates allowed the samples to get recrystallized in three different ways: below Ac₁, just around Ac₁ and above Ac₁. {3 3 2} fiber texture along with {1 1 2} 1 1 1 texture component were observed after heating to the soaking temperature as well as after slow cooling. The overall intensity of the texture as well as textural component was observed to be nearly independent of the heating rate as well as cooling rate. The textural evolution was correlated with the volume fractions and morphology of carbides, which depend on the annealing processing parameters.     

Impact properties of laminated angle ply composites

The impact properties of laminated composites have been studied as a function of fiber orientation angle, lamination configuration and specimen geometry. The energy absorbing mechanisms havebeen identified. The impact properties of laminated composites are influenced significantly by the fiber orientation angle, lamination configuration and specimen geometry. All off-axis composites (0° < θ < 90°) fail by brittle inter-fiber cleavage mode with little or no interlayer delamination. The longitudinal composites (θ = 0°), both unidirectional and crossplied, fail by a combination of failure modes which take place in a sequential manner—fiber failure and interfacial splitting followed by a layer-to-layer delamination. The presence of 0° layer(s) in transverse composite (θ ±90°) improves their impact performance.     

Structure, texture and mechanical properties of AlZnMgCuZr alloy rolled after heat treatments

The aluminium alloy containing 6.7 wt.% Zn, 2.6 wt.% Mg, 1.6 wt.% Cu and 0.1 wt.% Zr was continuously cast and either quenched from 465°C, or furnace cooled down to 100°C to find the best ductility for further cold plastic deformation. The alloys were then cold rolled down to the highest possible degree of deformation. The initial texture in both alloys can be described by (211)[111], (321)[346] and (110)[112] ideal orientations. With increasing deformation other orientations like {110}001 and cubic {100}001 appear after both types of treatments. TEM studies revealed increase of subgrain misorientation up to approx. 9° after 75% of deformation by rolling. On ageing at 120°C for 24 h the maximum hardness of 210 HV was reached. The alloys deformed prior to ageing at 120°C attained 230 HV. Very small GP zones, up to a few nanometers in size, grow after several days of ageing giving diffused diffraction effects. After ageing for 1 day at 120°C, precipitates grow and were identified as η′.     

Tungsten chemical vapor deposition using tungsten hexacarbonyl: microstructure of as-deposited and annealed films

Tungsten (W) films were deposited on Si(100) from tungsten hexacarbonyl, [W(CO)₆], by low-pressure chemical vapor deposition (CVD) in an ultra-high vacuum (UHV)-compatible reactor. The chemical purity, resistivity, crystallographic phase, and morphology of the deposited films depend markedly on the substrate temperature. Films deposited at 375°C contain approximately 80 at.% tungsten, 15 at.% carbon and 5 at.% oxygen. These films are polycrystalline β-W with a strong (211) orientation and resistivities of >1000 μΩ cm. Vacuum annealing at 900°C converts the metastable β-W to polycrystalline -W, with a resistivity of approximately 19 μΩ cm. The resultant -W films are porous, with small randomly oriented grains and nanoscale (<100 nm) voids. Films deposited at 540°C are high-purity (>95 at.%) polycrystalline -W, with low resistivities (18–23 μΩ cm) and a tendency towards a (100) orientation. Vacuum annealing at 900°C reduces the resistivity to approximately 10 μΩ cm, and results in a columnar morphology with a very strong (100) orientation.     

Oriented growth of silicide and carbon in SiC-based sandwich structures with nickel

We report on the formation kinetics and the metal-mediated structuring in nanoregions of silicide and carbon containing interlayers in SiC-based materials. The silicide formation and the graphite texturisation are determined by complex reactive diffusion processes. High resolution and analytical electron microscopy evidenced a δ-Ni₂Si growth with a 5 0 6 fibre texture in parallel orientation to the 0 0 0 1 direction of the SiC substrate. The oriented growth of graphitic regions in the silicide hints to a diffusion controlled carbon precipitation from the silicide supersaturated with carbon, explaining the observed orientation relationships between graphite and silicon carbide: perpendicular and parallel to the {0 0 0 1} silicon carbide surfaces.     

The influences of alloying additions and processing parameters on the rolling microstructures and textures of magnesium alloys

The combined effects of lithium additions (1–3 wt%) and processing parameters (rolling temperature, annealing) on the microstructural and texture evolution of pure Mg and Mg–3 wt% Al–1 wt% Zn alloy have been studied. Following rolling the basal planes were aligned with the sheet surface, although the basal poles were split and rotated towards the rolling direction. Lithium additions increased the rotation of basal poles in the rolling and transverse directions; an increase in the rolling temperature was associated with decreased rotation in the rolling direction and some broadening of texture in the transverse direction. Recrystallization during rolling varied between alloys, but had little influence on the texture. Recrystallization, and particularly grain growth, during annealing resulted in a single peak in the basal poles replacing the split observed following rolling. Texture is interpreted in terms of deformation, recrystallization and grain growth. Microstructural and texture evolution during industrial forming processes are also discussed.     

Grain size effects on the tensile properties and deformation mechanisms of a magnesium alloy, AZ31B, sheet

The grain size dependence of the tensile properties and the deformation mechanisms responsible for those properties are examined for Mg alloy, AZ31B, sheet. Specifically, the Hall–Petch effect and strain anisotropy (r-value) are characterized experimentally, and interpreted using polycrystal plasticity modeling. {1 0 . 2} extension twins, {1 0 . 1} contraction twins, and so-called “double-twins” are observed via microscopy and diffraction-based techniques, and the amount of twinning is found to increase with increasing grain size. For the sheet texture and tensile loading condition examined, {1 0 . 2} extension twinning is not expected, yet the polycrystal plasticity model predicts the observed behavior, including this ‘anomalous’ tensile twinning. The analysis shows that the Hall–Petch strength dependence, of the polycrystal as a whole, is primarily determined by the grain size dependence of the strength of the prismatic slip systems.     

Influence of substrate on the pulsed laser deposition growth and microwave behaviour of KTa0.6Nb0.4O3 potassium tantalate niobate ferroelectric thin films

Thin films of potassium tantalate niobate KTa_0.6Nb_0.4O₃ (KTN) were grown by pulsed laser deposition on five different substrates suitable for microwave devices: (100)MgO, (100)LaAlO₃, (1–102)sapphire (R-plane), (0001)sapphire (C-plane) and alumina. The high volatility of potassium at the film growth temperature required the addition of an excess of potassium to the ablation target. For optimized deposition conditions, Rutherford backscattering showed that the KTN films had a 1: 1 atomic ratio for K:(Nb + Ta). As grown KTN thin films were single-phase, without any particular orientation on sintered alumina, whereas an epitaxial growth with the (100) orientation was achieved on (100)MgO and (100)LaAlO₃ with a mosaicity Δω_(100)KTN close to 0.7°–1.5° and  0.4°–0.9°, respectively, attesting a high crystalline quality. In contrast, growth of KTN on R-plane sapphire results in a texture with the (100) orientation and the presence of the (110) orientation as a secondary one. The room temperature measurements carried out on Au interdigited capacitors patterned on KTN coated (100) LaAlO₃ and sapphire led at 1 GHz to an agility ΔC / C  4.6% and  7.2%, respectively, for a moderate applied field of 15 kV cm^− 1. Stubs patterned on the same systems led to an agility ΔF_r / F_r of  2.2% and 4.2%, respectively, for F_r = 7 GHz and the same applied field.     

The Dislocation Structure of a Single-Crystal γ + γ′ Two-Phase Alloy After Tensile Deformation

The dislocation structures of an industrial single-crystal γ + γ′ two-phase alloy DD3 after tensile deformation from room temperature to 1273K were studied by transmission electron microscopy. The strength of this alloy decreased with an increase in the temperature, and showed a strength peak at 1033K. At room temperature, the dislocations shearing the γ′ particles were found to be 1/3<112> partial dislocations on the dodecahedral slip system <112>{111}. Some dislocation pairs on the cubic <110>{100} system that blocked the glide of dislocations were found at a medium temperature of 873K. As a result, dislocation bands were formed. Shearing of γ′ particles by 1/3<112> partial dislocations on the dodecahedral slip system <112>{111} was also found at this temperature. At the peak temperature of 1033K, because of the strong interaction between dislocations on the {111} and {100} planes, the extent of dislocation bands with high dislocation densities was extensive. The 1/3<112> partial dislocations on the dodecahedral slip system <112>{111} also existed. When the temperature reached the high temperature of 1133K, the range of dislocation bands was limited. The γ′ particles were sheared by <110> dislocation pairs on the octagonal <110>{111} system and the cubic <110>{100} system. At 1273K, the regular hexagonal dislocation networks were formed in the γ matrix and at the γ/γ′ interface. The Burgers vectors of the network were found to be b₁ = 1/2[110], b₂ = 1/2[1–10], b₃ = [100], and the last one was formed by the reaction of b₁ + b₂ → b₃. Dislocations shearing the γ′ particles were found to be <110> dislocation pairs on the octagonal system <110>{111} and cubic slip system <110>{100} at 1273K.     

On the cold rolling textures in some fcc Ni–W alloys

The development of thin, mechanically stronger and highly cube textured substrates is of great technological importance for increasing the engineering current density of coated superconductors. Due to the development of a strong recrystallisation cube texture and improved strength, Ni–W alloys are good candidate substrate materials for the development of coated superconductors. It is well known that the recrystallisation cube texture is strongly related to the rolling texture, which in turn is related to the alloying content, temperature of deformation, etc. In the present paper, we report the copper-type to brass-type texture transition in the rolling texture of cold rolled fcc Ni_1−xW_x alloys at W contents >5 at.%. The possible reasons for the above texture transition and the consequences on recrystallisation texture are discussed.     

Domain patterns on ferroelectric Rh:BaTiO3 single crystals

Single crystal growth and domain structure of Rh:Barium titanate (BaTiO₃) have been investigated. Rh doping in BaTiO₃ is effective for the growth of bulk crystals without twin formation. Atomic force microscope (AFM) and optical microscope studies reveal the formation 180° and 90° domains on the grown crystals. It has been observed that the complex 180° domain structure with typical size of around 20 μm exists in the c-domain of {0 0 1} face of Rh doped BaTiO₃ crystals.     

Morphology of sputter deposited Al alloy films

Morphology of Al–2.0at%Ta and Al–2.0 at.% Nd alloy films before and after annealing was investigated for applications of interconnections for liquid crystal displays. It was found that the morphology and the microstructure of Al–2.0 at.% Nd alloy films changed markedly by annealing at the temperature region from 200°C to 300°C, while the morphology of Al–2.0 at.% Ta alloy films did not change by annealing up to 400°C. For the case of Al–2.0 at.% Nd alloy films, the incline of the <111> fiber texture to the substrate normal was observed during annealing. Structural characteristics of the Al films were investigated by TEM, SAD and XRD to determine the influence of alloying elements on the morphology and the fiber texture. From these results, it was concluded that the microstructures strongly influence the morphology and the grain orientation of Al alloy films.     

Thermomechanical treatment for enhancing gamma fiber component in recrystallization texture of copper-bearing bake hardening steel

A two-step rolling-annealing process has been developed to increase the 〈1 1 1〉//ND (γ fiber) component in the recrystallization texture of a copper-bearing bake hardening steel. The two step process comprises the first rolling by a low reduction in thickness and subsequent annealing at 780 °C, followed by the second rolling by a high reduction and subsequent annealing at 780 °C. The first rolling process aims at seeding the γ fiber oriented grains, so that they can grow at the expense of differently oriented grains developed in the second rolling process. In this way the density of γ fiber component in the recrystallization texture of the bake hardening steel much increases compared with that in the conventional one-step rolling-annealing process.