Crystal orientation in Ni-Mn-In melt-spun ribbons

The crystal orientation of Ni₅₀Mn₂₅In₂₅ and Ni₅₀Mn₃₄In₁₆ melt-spun ribbons which appears parent phase at room temperature was investigated in this paper.The grains grow perpendicular to the surface of the ribbon and show columnar crystals distinctly.X-ray diffraction and electron backscattered diffraction were used to identify the orientation information of the ribbons.It is indicated that the well-developed preferred orientation ...     

Preparation of highly preferred orientation TiB2 coatings

This paper focuses on the preparation of titanium diboride （TiB2） coatings on the graphite substrate by continuous current plating （CCP） and pulse current plating （PIC） electrochemical techniques in fluoride electrolytes （LiF-NaF-KF） containing K2T1F6 and KBF4 as the electrochemically-active components at 700℃. Thick leveled and uniform coatings were obtained and were composed of relatively pure TiB2. The effect of the experimental parameters on the microstructure of the coatings was studied. The results showed the electrodeposition with PIC produced coatings with better quality, when compared with those obtained by CCP, under the conditions of the current density i = 0.6 A/cm^2, frequency = 100 Hz, and todtofr = 4/1. XRD analysis indicated that the preferred orientation of coatings is （110） plane, which is in accordance with the prediction of the two-dimensional crystal nuclei theory. The effect of a ratio of ton/toff and frequency on the crystal size, textule coefficient and microstress was also investigated.     

Cube orientation in hot rolled high purity aluminum plate

X-ray diffraction and orientation mapping in EBSD measurement were applied to obtain information of deformation and recrystallization with the emphasis on the cube orientation in hot rolled high purity aluminum plates.It is shown that cube orientations are retained to a large extent during hot rolling.Some deformed cube grains are found to have experienced large extent of recovery according to their Kikuchi band contrasts.The deformed cube-oriented grains in hot rolled plates are in an unfavorite growth condition with respect to their neighboring grain orientations for the subsequent annealing.The reasons for the phenomena observed,as well as the influence of hot rolling process on subsequent cold rolling and final annealing were discussed.     

Strain-induced orientation of copper oxide nanoislands through decomposition of pre-organized copper nitrate

By the decomposition of copper nitrate at 400℃, oriented islands of copperoxide crystals were suceessfully fabricated on the amorphous glass surface. X-ray diffraction (XRD), atom force microscope (AFM), and X-ray photoelectron spectroscopy (XPS) confirm the presence of copper oxide islands. The formation of oriented island structures is attributed to the following reasons: 1) the mismatch between the glass substrate and the copper oxide crystals during the relaxation of thermal expansion leads to the formation of islands; 2) the preorganized copper nitrate particles in the voids of colloidal crystals determine their ordered spatial distribution; 3) the strain of the glass substrate developing during calcination provides the driven energy for the orientation of copper oxide crystals along the same direction.     

Crystal preferential orientation ofAl-1.0%Si alloy in continuous unidirectional solidification process

Al-1.0%Si alloy rods containing unidirectional microstructures were fabricated by continuous unidirectional solidification （COS） process. The crystal growth orientation evolution of Al-1.0%Si alloy in CUS process was studied. The microstructure was observed and the orientation results examined by electron back scattering diffraction（EBSD） indicate that at the beginning of COS process the crystals grow along a certain preferred orientation, （100）direction, but there are also other growth directions deflecting from this preferred orientation. It is found that as directional solidification continues, the crystals with high growth speed remain and those with low growth speed vanish. The crystal preferred orientation tends to be （100）direction in competition growth process. Namely, the （100） fiber texture oral-1.0%Si alloy rod becomes stronger in the stable directional solidification establishing process. When the solidification parameters remain stable, the crystal growth orientation also obtains in steady state. Once the technological parameters fluctuate, the stray crystals deviating from the preferred orientation appear. After the process of competition growth the crystals regain strong preferred orientation. The orientation distribution function（ODF） results also testify the above conclusions.     

Grain size and orientation distributions: Application to yielding of α-titanium

A method to incorporate grain size effects into crystal plasticity is presented. The classical Hall–Petch equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or variable grain size distributions. These deficiencies can be negated by incorporating both grain size and orientation characteristics into crystal plasticity theory. Augmented homogenization relationships based on a viscoplastic Taylor-like approach are introduced along with a new function, the grain size and orientation distribution function (GSODF). Estimates of the GSODF for rolled high-purity α-titanium are recovered through multi-section orientation imaging microscopy using chord length measurements to quantify grain size. It is illustrated that considerable variation in the grain size distribution occurs with lattice orientation in this material. Yield surface predictions calculated from the augmented and traditional models indicate that grain size distribution as a function of lattice orientation may play a significant role in explaining the large yield strength anisotropy of rolled α-titanium.     

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.     

Continuous recrystallization in pure Al 1.3% Mn investigated by local orientation analysis

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Enhancement of the orientation and adhesion of Al films on LiNbO3 with Ni underlayer

1 Introduction Al films are widely used in surface acoustic wave (SAW) devices for mobile communication systems. In the SAW devices, the input electrical signals are transformed to SAW signals propagating on a piezoelectric substrate by interdigital elect…     

Heat transfer of an evaporator–condensing system with electrohydrodynamic coolant circulation and different spatial orientation

The influence of the spatial orientation of an evaporator–condensing system (ECS) on the heat transfer coefficient is considered. As found, it varies according to the cosine law, which implies that it is at its minimum when the evaporator is in the top position, and it is at its maximum when the heater is in the bottom position. This is consistent with the physical considerations about the effect of buoyancy forces on heat transfer. The average velocity of coolant circulation through the ECS loop is found, and on this basis, the “electric” Reynolds number and heat transfer coefficient are estimated. The influence of pressure on heat transfer in the ECS has been analyzed. The considered phenomena have been physically interpreted; they agree well with the experimental data.     

Microstructural features and orientation correlations of non-modulated martensite in Ni–Mn–Ga epitaxial thin films

Epitaxially grown thin films with nominal composition Ni₅₀Mn₃₀Ga₂₀ and thickness 1.5 μm were prepared on MgO(1 0 0) substrate with a Cr buffer layer by DC magnetron sputtering. The surface layer microstructures of the as-deposited thin films consist of non-modulated (NM) martensite plates with tetragonal structure at ambient temperature, which can be classified into the low and high relative contrast zones of clustered plates (i.e. plate colonies) with parallel or near-parallel inter-plate interface traces in secondary electron images. Orientation analyses by electron backscatter diffraction revealed that individual NM plates are composed of alternately distributed thicker and thinner lamellar variants with (1 1 2)_Tetr compound twin relationship and coherent interlamellar interfaces. In each plate colony, there are four distinct plates in terms of the crystallographic orientation of the thicker lamellar variants and therefore, in total, eight orientation variants. For the low relative contrast zones, both thicker and thinner lamellar variants in adjacent plates are distributed symmetrically across their inter-plate interfaces (along the substrate edges). At the atomic level, there are no unbalanced interfacial misfits and height misfits, resulting in long and straight inter-plate interfaces with homogeneous contrast. However, in the high relative contrast zones, the thicker and thinner lamellar variants in adjacent plates are oriented asymmetrically across their inter-plate interfaces (at ～45° to the substrate edges). Significant atomic misfits appear in the vicinity of the inter-plate interfaces and in the film normal direction. The former result in bending of the inter-plate interfaces, and the latter give rise to the high relative contrast between adjacent plates.     

Induced effects of Cu underlayer on（111） orientation of Fe50 Mn50 thin films

Effects of Cu underlayer on the structure of Fe50 Mn50 films were studied. Samples with a structure of Fe50 Mn50 (200 nm)/Cu(tcu) were prepared by rnagnetron sputtering on thermally oxidized silicon substrates at room temperature. The thickness of Cu underlayer varied from 0 to 60 nm in the intervals of 10 nm. High-vacuum annealing treatments, at different temperatures of 200, 300 and 400℃ for 1 h, respectively, on the Fe50Mn50 (200 nm)/Cu(20 nm) thin films were performed. The surface morphologies and textures of the samples were measured by field emission scan electronic microscope (FE-SEM) and X-ray diffraction(XRD). Energy dispersive X-ray spectroscopy (EDX) and Auger electron spectroscopy(AES) were used to analyze the compositional distribution. It is found that Cu underlayer has an obvious induce effect on (111) orientation of Fe50 Mn50 thin films. The induce effects of Cu on (111) orientation of Fe50 Mn50 changed with the increase of Cu layer thickness and the best effect was obtained at the Cu layer thickness of 20 nm. High-vacuum annealing treatments cause the migration of Mn atoms towards surface of the film and interface between Cu layer and substrate. With the increasing annealing temperature, migration of Mn atoms is more obvious, which leads to a Fe-riched Fe-Mn alloy film.     

Unified rationalization of the Pitsch and T–H orientation relationships between Widmanstätten cementite and austenite

This work demonstrates that understanding the habit planes of cementite plates is an important step to gain an insight into the irrational orientation relationships (ORs) between Widmanstätten cementite and austenite, i.e. the Pitsch and T–H ORs. A reproducible irrational OR in this system is attributed to a unique correspondence between the OR and the habit plane, under the condition that the habit plane is a quasi-invariant plane. The OR is constrained by two parallelism conditions: parallelism of [0 1 0]_C and 〈1 1 0〉_A; parallelism of a group of Δg’s in the zone axis of [0 1 0]_C. The calculated ORs and habit planes are fully consistent with the experimental results from the literature.     

Influence of Cu content on microstructure,grain orientation and mechanical properties of Sn–xCu lead-free solders

The effect of Cu content on the microstructure, grain orientation and mechanical properties of Sn–xCu (x=0–4.0 wt.%) lead-free solder was studied. Results showed that added Cu induced the formation of intermetallic phases. Only the η-Cu₆Sn₅ and ?-Cu₃Sn phases were present in the β-Sn matrix. For all contents, the strongly preferred orientation of the β-Sn phase was formed on the {001} plane. In Sn doped with 1.0 wt.% Cu, the η-Cu₆Sn₅ phase exhibited the preferred orientation of {0001} plane, whereas doping with 3.0 or 4.0 wt.% Cu transformed the preferred orientation to the {010} plane. In addition, only the {0001} and planes were present in the ?-Cu₃Sn phase. The high Cu contents contributed to an increased number of low-angle boundaries, high residual strain, tensile strength and microhardness.     

The effect of grain orientation on fracture morphology during high-cycle fatigue of Ti–6Al–4V

Three different product forms of Ti–6Al–4V, unidirectionally rolled and cross-rolled plate and forged bar, have been cyclically loaded within the high-cycle fatigue regime to investigate fatigue crack initiation. The fracture surfaces of fatigued specimens contained large regions of neighbouring facets. The majority of facets examined had a near-basal fracture plane. It was shown that grains favouring crack initiation were primarily those with misorientations between 15° and 40° from the loading direction, whereas other orientations served as crack growth paths. This implies that the formation of a facet requires a combination of a moderately high Schmid factor for basal slip coupled with a tensile component perpendicular to the basal plane. The large regions of neighbouring facets on the fracture surface were found to be a consequence of cracking within a macrozone unfavourably oriented for slip found within the microstructure, i.e. one with its c-axis near to the loading direction.     

Evolution of {001}<110> orientation and related lattice rotation of Al alloy 6111 during rolling

The texture evolution and lattice rotation in Al alloy 6111 with an initial {001} <110> component during symmetrical and asymmetrical rolling were investigated by means of orientation distribution function(ODF). The results show that the as-rolled initial {001}<110 > entation evolves into not only the copper orientation but also all the other orientations along the β fiber, including the brass orientation, by lattice rotation around special directions. Compared with the symmetrical rolling, the {001}<110 > component in the surface layer on the slower roller side evolves more quickly into the orientations along the β fiber during asymmetrical rolling, while that in the surface layer on the faster roller side evolves more slowly.     

Effect of the orientation of defects on the load‐carrying capacity of welded joints weakened by soft interlayers

The results of the investigations of the effect of the shape of the current decrease curve at the moment of completion of welding on the thermal cycle of welding up the crater and the shape of the surface of the shrinkage cavity are presented. The kinematics of solidification of the weld pool during the final stage of welding is investigated. The optimum shape of the current decrease curve for minimizing the dimensions and optimizing the shape of the shrinkage cavity is determined.     

Phenomenological observations of lamellar orientation effects on the creep behavior of Ti–48at.%Al PST crystals

The anisotropy in creep behavior of a PST crystal was examined using crystals of the composition Ti–48Al in three different orientations, φ=0°, 45° and 90°, in the temperature range of 700–815°C. In addition, a fully lamellar Ti–48Al polycrystal of similar lamellar spacing was also tested under identical conditions for comparison. Significant anisotropy was observed at all the three temperatures of test. In both primary and secondary stages, the 0° PST material was consistently the strongest and the 45° the weakest, with the polycrystal behaving much like the 45° PST crystals. The anisotropy could not be rationalized based on either Schmid factor differences or α₂ anisotropy. The beneficial effects of orientation are observed to be similar to those of alloying additions of C or Si. It is anticipated that fully lamellar textured polycrystals will be significantly superior to polycrystalline materials having a random grain orientation in both primary and secondary-stage creep behavior.     

Effect of grain boundary orientation on radiation-induced segregation in a Fe–15.2 at.% Cr alloy

Ferritic chromium steels are important structural materials for future nuclear fission and fusion reactors due to their advantages over traditional austenitic steels, such as higher thermal fatigue resistance, lower thermal expansion coefficients and reduced swelling. However radiation-induced segregation or depletion (RIS/RID) of solute atoms at grain boundaries in these materials is a concern because these phenomena could adversely affect their mechanical properties. In an effort to develop a full mechanistic understanding of RIS/RID, a systematic approach combining orientation imaging, site-specific specimen preparation and three-dimensional atomic-scale analysis has been developed to characterize the behaviour of Cr and C at grain boundaries during irradiation. This methodology has been applied to a Fe–15.2 at.% Cr alloy to investigate the effects of grain boundary misorientation, irradiation depth and impurities. Systematic differences in Cr segregation are reported as a function of grain boundary character and irradiation conditions. The similar properties demonstrated by grain boundaries of similar type means that it should be possible to apply relatively simple models to predict the long-term behaviour of these materials under irradiation conditions.     

A study on the formation mechanisms of butterfly-type martensite in Fe–30% Ni alloy using EBSD-based orientation microscopy

The spatial orientation distribution and crystal orientation relationships (ORs) between a butterfly-type martensite (α′) plate and its austenite matrix (γ) in Fe–30% Ni alloy were investigated in detail. One α′–γ interface of the α′ plate mainly exhibits a G–T (Greninger–Troiano) OR, while the other side shows both Kudjumov–Sachs and G–T ORs. It is proposed that the difference between the two sides arises due to a change of the accommodation process for transformation strain during the growth of α′. Moreover, orientations inside the α′ plate continuously change from the one α′–γ interface to the other. A similar orientation change is observed in the γ matrix but only on one side of the plate. These orientation gradients have a common rotation axis and are explained in terms of dislocation inheritance during the growth of the α′ plate. Based on the local changes of ORs at α′–γ interface and the orientation gradients inside α′ and γ, the α′ formation process is discussed.