Small Grain Structure Research Articles

A study of the structural properties of sputtered CoCrPt based on x-ray diffraction, small angle x-ray scattering, XAFS, and transmission electron microscopy measurements (abstract)

As a first step in trying to understand the relationship between magnetic properties and structural properties, the authors have conducted a systematic structural investigation of CoCrPt samples that have been sputtered at different levels of sputtering power, which affects magnetic properties. X-ray diffraction (XRD), small angle x-ray scattering (SAXS), and XAFS were used to examine, respectively, long, medium, and short range orderings. TEM was used to examine the structural morphology. CoCrPt was fabricated on Kapton films by dc magnetron sputtering at levels of 0.1, 0.3, 0.5, and 1 kW sputtering power. XRD indicated a continuous increase in the intensity of the peak corresponding to hcp (002), as sputtering power was increased. SAXS, on the other hand, in the range of 0.5–3.0 deg. at 2θ, indicated the presence of scattering for the 0.1 and 0.3 kW samples alone, not for the others. Similarly discontinuous were the spectrums produced by XANES of Co for the 0.3, 0.5, and 1.0 kW samples, which resembled the spectrum of sputtered Co. The spectrum of the 0.1 kW samples was quite different. TEM indicated a clear small-grain structure for the 0.1 kW sample, less clearly defined grains for the 0.3 kW sample, and no observable grains for the others. When conducted after chemical etching, it further identified the source of the grain structure as Pt segregation. This leads to speculation that Pt segregation may be responsible, to some degree, for the discontinuity observed in SAXS and XANES measurements. It is further speculated that the long range ordering (crystal orientation) is quite probably related to magnetic anisotropy, and that segregation affects wall motion, which means that, in order to understand the relationship between magnetic and structural properties, structural investigations should be systematic and include short, medium, and long range orderings.

真空Ｐｓｅｕｄｏ‐ＨＩＰにより合成されたＴｉＡｌ系金属間化合物の組織と強度の温度依存性

A pseudo-HIP (PHIP) process has been applied for the reactive synthesis of near-net shape Ti-Al intermetalic compound materials. Ti-Al compound specimens of full density with composition range Ti-46 to 52at%Al were obtained after PHIP treatment at 1373K to 1623K. The high temperature bending strength of the Ti-48at%Al increased by increasing PHIP temperature. After PHIP treatment at 1623K the volume percent of lamellar structure increased by increasing the Ti content and a full lamellar structure of The Ti-46at%Al gave the highest strength. A structure of matrix gamma and small lamellar grains that was obtained in the range of Al rich composition had high yield strength at high temperature.

Superconducting high-J c coatings on copper substrates by RF magnetron sputtering

Stoichionetric YBa 2 Cu 3 O 7- x thin superconducting films were deposited on copper foils with intermediate buffer layers of Ti and MgO using RF magnetron sputtering. Rapid thermal annealing was applied to the films and polycrystalline c-axis oriented films were obtained. The speed of heating was found to correlate with the grain size in the coating. The critical current density and transition temperature were measured under magnetic field both parallel and perpendicular to the substrate. The films with large-grain structure showed remarkable resistance to the magnetic field while small-grain structures were not resistant. The highest zero-resistance transition temperature obtained after thermal annealing was 85.9 K and a critical current density at 78 K without magnetic field was 15 400 A/cm 2.

Some effects of grain shape and varying external magnetic fields on the magnetic structure of small grains of magnetite : Williams, W; Dunlop, D J Phys Earth Planet InterV65, N1/2, Dec 1990, P1–14

Some effects of grain shape and varying external magnetic fields on the magnetic structure of small grains of magnetite : Williams, W; Dunlop, D J Phys Earth Planet InterV65, N1/2, Dec 1990, P1–14

Some effects of grain shape and varying external magnetic fields on the magnetic structure of small grains of magnetite

The change in the magnetic spin structure of simple domain configurations has been investigated as a function of grain size, shape and varying external magnetic fields at elevated temperatures. The results indicate that simplification of domain configuration occurs as grains become elongated, and as grain sizes increase from small pseudo-single-domain (PSD) to large PSD. In these cases domains become nearly lamellar, as suggested by earlier Bitter pattern observations on large PSD grains of magnetite, although the spins on the crystal surface in the theoretical models would not produce the Bitter lines representative of its body domain structure. Simulation of domain rotation under the influence of an external uniform magnetic field shows that the rotation mode depends upon the grain's temperature. At higher temperatures coherent rotation is favoured, whereas at lower temperatures the non-uniform domain structure prohibits coherent rotation and forces a wave-like transition via a lamellar three-domain stage.

Transmission Electron Microscopic Study of Electroless Nickel-Molybdenum-Boron Alloy Films

The structure of amorphous and crystalline electroless Ni–Mo–B films was studied by transmission electron microscopy (TEM). The amorphous film in as-deposited conditions was of a completely disordered state with few crystalline regions. This film crystallized by means of nucleation after 300°C annealing; the produced nuclei grew large after 500°C annealing. Two crystalline films in the as-deposited state, plated from 0.005 and 0.010 mol dm-3 Na2MoO4 concentration baths, showed different annealing behavior even though they had almost identical Ni and Mo composition. The former contained amorphous-like regions corresponding to an intermediate state between the amorphous and the crystalline. The latter film was so stable against annealing that the structure of small grains was maintained after 500°C annealing.

Absorption edges of mixed silver-halide crystals and polycrystalline optical fibers

Optical absorption edges of mixed AgClxBr1−x (0≤x≤1) crystals and polycrystalline fibers were investigated as a function of composition. Both visible edge, resulting from electronic transitions, and infrared edge due to multiphonon processes behave as the one-mode (amalgamation) type of mixed crystals, shifting continuously with composition. Quantitative expressions were used to discuss the results. Polycrystalline extruded fibers preserve this spectral window of silver-halide crystals, except for slight deviations which are explained by the small-grain structure of the fibers.

Transmission Electron Microscopic Study on Electroless Plated Nickel-Molybdenum-Phosphorus Alloy Film

In order to clarify the cause of the particular annealing behavior of resistivity of electroless Ni–Mo–P alloy films, the film structure after various heat treatment of a typical crystalline Ni-Mo-P alloy film by electroless plating was investigated by transmission electron microscopy (TEM). In the Ni–Mo–P film under as-plated conditions, the lattice image is observed, but it contains some regions having no lattice images due to amorphous conditions. The structure of small grains is kept even after heat treatment at 400°C, but the nonuniformity of Mo concentration is confirmed to exist in the film. After heat treatment at 700°C, the grains become larger and crystals with complete lattice images and no defects are observed. The results support the annealing effect of resistivity of the crystalline Ni–Mo–P alloy film, which shows a maximum upon heat treatment at around 400–500°C.

Amorphous Ni-P alloys prepared by ion implantation

Abstract Ion implantation of 40 keV, P+ ions into pelycrystalline Ni foils has been used to produce amorphous Ni-P alloys. The foils were subsequently investigated by electron microscopy and electron diffraction. The diffraction measurements confirm the presence of an amorphous surface layer. The ion implanted alloy is compared to similar material produced by the more usual techniques of electro deposition and vapour quenching. After annealing, the implanted layer recrystallizes into a dense, small grained structure. Equivalent results have been obtained using Co and Fe as target materials. The data suggests that ion implantation should contribute to an understanding of the production and stability of amorphous metals.

Variation of stress relaxation of titanium alloys as a function of the conditions of deformation at high temperatures

1. Forging of the VT3-1 and VT14 alloys at temperatures of the β-region leads to the formation of large grains, a nonuniform, large-needle microstructure, low ductility (particularly the reduction in section), and low resistance to relaxation. 2. The decrease of the initial forging temperature to the temperature of the α+β region, other conditions being equal, leads to the formation of a more uniform equiaxial and small-grained structure and increases the ductility and the relaxation resistance. 3. An increase of the testing temperature of the VT3-1 alloy to 100°C has no effect on the resistance to stress relaxation during the 1000 h of testing; in the case of the VT14 alloy the relaxation resistance decreases. The resistance of the VT3-1 alloy to stress relaxation is higher than that of the VT14 alloy and of the 60Kh3G8N8V alloy used at the present time for banding. 4. The VT14 alloy is more susceptible to deformation at high temperatures than the VT3-1 alloy not only in terms of its mechanical characteristics but also in terms of resistance to stress relaxation.

Influence of heat treatment on the structure and properties of VT1 titanium and the OT4 alloy

1. Sheets of technically pure commercial VT1 titanium as delivered have a small grained structure with the grain size corresponding to grade 7-6. 2. Heating in air at 650°C leads to a considerable increase in the surface hardness of VT1 titanium. The microhardness on the surface of the sheet is H 405; it is H 196 in the center. 3. Heating of VT1 titanium and the OT4 alloy for 2 h at 750–850°C leads to the saturation of the surface layer with gases and, as the result, a gray oxide film 15 microns thick is formed with a hardness of H 727 in the case of VT1 titanium and H 1030 in the case of the OT4 alloy. 4. Heating above the temperature of allotropic transformation (from 950 to 1050°C) leads to the formation of a white oxide film with a higher hardness on the surface of VT1 titanium and the OT4 alloy: H 1079 in the case of titanium and H 1300–1410 in the case of the OT4 alloy. Under the oxide layer there is a very hard diffusion layer. The depth of penetration of oxygen into the metal depends on the temperature and heating time.

Difference in the grain sizes of Ni?Cr alloys resulting from uniform deformation

1. A structure consisting of grains of different sizes occurs in alloys of the KhN77TYu type after relatively uniform deformation and during subsequent standard heat treatment as the result of either incomplete recrystallization or incomplete collecting recrystallization. 2. A uniform small grained structure occurs after the completion of recrystallization and a uniform large grained structure after complete collecting recrystallization. 3. It is assumed that the thermal effect occurring in areas of local deformation has a significant influence on the formation of the large grained structure in the KhN77TYu alloy.

Factors affecting the wear of babbit bearings and steel machine parts

The main factor in the wear of steel shafts running in babbit bearings is the grain size of the SnSb inclusions, which depends on the method of depositing the babbit. A small-grain structure decreases the wear of the babbit but somewhat increases the wear of the steel.

Microstructure of the 12KhMF steel after deformation and aging

1. Prolonged aging of undeformed 12KhMF steel at 580°C induces large accumulations of carbides in the grains and along the grain boundaries. 2. Deformation and subsequent aging induce precipitation of small carbides along the slip lines in ferrite grains and along the block boundaries and in the mosaic. These carbides increase the resistance of the metal to deformation. 3. A 15% deformation and 10,000 h aging induce the maximum number of small paticles per unit area, which produces high resistance to creep and increases the time before the steel ruptures at high temperatures. A 25% deformation leads to coagulation of particles and to the concentration of these particles in the slip bands. 4. An increase of the deformation from 7 to 25% leads to the fragmentation of the mosaic blocks, and this structure is not affected by 10,000 h aging at 600°C. This small-grained structure is responsible for the increase of the time before rupture of 12KhMF steel at high temperatures.

High-strength nonmagnetic steel

1. 25Cr17Ni4G15AF2 steel has a high yield point (σ0.2>80 kg/mm2) and satisfactory plasticity (αk = 4 kgm/cm2) after quenching from 1180°C and aging 10 h at 700°C. 2. Vanadium strengthens this steel because it favors the precipitation of carbonitrides and the formation of the σ-phase, and also because of the small-grain structure produced.

On the Mechanism of Cathodic Crystal Growth Processes

An electron diffraction and electron microscopic study on thin films of copper electrodeposited on clean 1 mil foils of copper and platinum from acid‐copper and complex copper‐glycine baths maintained at 25 °C has been conducted. The foils of copper and platinum consist of small grained structure. Results show that for a current density of 10 ma/cm2 and high acidic conditions (pH 0.3 or 0.9), large crystal grains of copper (10–40µ) are developed, even when the deposit thickness is very small. A limited study on the effect of current density on the orientation of nickel, electrodeposited mainly on brass disks from some common plating solutions maintained at 25 °C, has also been carried out. Results are discussed in light of existing mechanisms for the cathodic crystal growth process.