Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500–800°C to total strains of ~4, followed by annealing at 800–1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28–0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3ⁿ CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D₀). The fraction of Σ3ⁿ CSL boundaries sharply rose to approximately 0.5 in the range of D/D₀ from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3ⁿ CSL boundaries slowed down significantly in the range of D/D₀ > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3ⁿ CSL boundaries in the recrystallized microstructure.     

Investigation of the transition to superplastic behaviour by measurements of electrical resistivity annealing curves

Superplastic behaviour of the Zn-0·25 wt. % Cd alloy is studied by means of electrical resistivity measurements accompanied by dynamical tensile tests and optical metallography. Specimens of the alloy were deformed at various strain rates and temperatures and then step-by-step annealed up to 520 K, the electrical resistivity changes due to annealing being recorded. It is shown that the resistivity annealing curves are strongly influenced by the value of strain, strain rate and deformation temperature. A good correlation between the mechanical characteristics of the alloy and the resistivity changes caused by annealing has been observed.     

Electrical properties of Cd,Zn and S ion-implanted layers in GaAs

The electrical properties of cadmium, zinc, and sulfur ion-implanted layers in gallium arsenide have been measured by the van der Pauw-Hall technique. Ion implantation was performed with the substrates held at room temperature. The dependence of sheet resistivity, surface carrier concentration, and mobility on ion dose and on post-implantation anneal temperature was determined. In the case of 60 keV Cd⁺ ions implanted into n-type substrates, a measurable p-type layer resulted when samples were annealed for 10 minutes at a temperature in the range 600—900°C. After annealing at 300—900°C for 10 minutes, 100 per cent electrical activity of the Cd ions resulted for ion doses ≤ 10¹⁴/cm².

The properties of p-type layers produced by implantation of 85 keV Zn⁺ ions were similar to those of the 60 keV cadmium-implanted layers, in that no measurable p-type behavior was observed in samples annealed below a relatively high temperature. However, in samples implanted with 20 keV Zn⁺ ions a p-type layer was observed after annealing for 10 minutes at temperatures as low as 300°C.

Implantation of sulfur ions into p-type GaAs substrates at room temperature resulted in the formation of a high resistivity n-type layer, evcn before any annealing was performed. Annealing at temperatures up to 200°C or above 600°C lowered the resistivity of the layer, while annealing in the range 300—500°C eliminated the n-type layer.     

Recrystallization of pure and strontium-doped KCl crystals

The kinetics of microstructure transformations are studied during annealing of deformed single crystals of KCl and KCl:0.05wt %Sr²⁺ at temperatures of (0.35–0.55)T _m (where T _m is the melting temperature) and during storage at room temperature. The effect of deformation rates ranging from 0.01 mm/min to 0.1 mm/min at a deformation temperature T _d=0.5T _m on the crystal structure and on the recrystallization kinetics is noted. It is found experimentally that the incubation period for static recrystallization in single-crystal KCl:0.05wt%Sr²⁺ is shortened and recrystallization takes place at room temperature after deformation in this temperature range. Here, during the new recrystallization grains have a twinned orientation with respect to the initial single crystal during the first stage and to the subgrains of the deformed crystal. As the annealing temperature is raised, the stage in which twins grow in KCl:0.05wt%Sr²⁺ crystals is shortened and it is displaced by recrystallization through migration of high-angle grain boundaries of the common type. Deformation conditions which ensure prolonged (at least three months) stability of the post-deformation hardening of single crystals are found experimentally for Sr²⁺-doped deformed single crystals. Fiz. Tverd. Tela (St. Petersburg) 41, 259–264 (February 1999)     

Defect recovery behavior of neutron irradiated molybdenum and tungsten of two purity levels

Abstract

The recovery behavior of radiation-induced defects during post-irradiation annealing was studied on molybdenum and tungsten specimens of two different purity levels. An electrical resistivity measurement technique at liquid nitrogen boiling temperature (～77°K) was used. Irradiation of both materials was conducted in Oak Ridge Research reactor at reactor ambient temperature (～70°C). The accumulative neutron fluence received was 7.3E+19 neutrons cm^?2 (E_n>l MeV) and 5.1E+20 neutrons cm^?2 (thermal). It was found that the number of recovery stages appeared to be independent of either the material or the impurity content. The stages are then believed to be due to the recovery of intrinsic defects and the recovery mechanisms are most likely the same for molybdenum and tungsten on the homologous temperature scale.     

Low energy boron and phosphorus implants in silicon (a) electrical sheet measurements

Silicon wafers were implanted in 〈111〉-direction with boron and phosphorus ions of 7 keV at room temperature. Doses between 10¹² and 10¹⁸ ions/cm² were applied. After successive annealing steps the electrical properties of the implanted layers have been determined by Hall effect and sheet resistivity measurements. The annealing characteristics of the implants depend on ion dose and species. Three annealing stages can be distinguished: (I) the temperature range below 500°C, (II) 500—700°C, (III) 700—900°C.

After annealing at 90°C the apparent electrical yield is proportional to dose for all implants and amounts to approx. 80 per cent for boron and 40 per cent for phosphorus.

Sheet resistivity vs. dose curves were derived for the annealing temperature of 400°C and used for the fabrication of position sensitive detectors. The position characteristics were found to be linear within ～1 per cent for resistive layers as long as 20 cm.     

Characteristics of electron beam evaporated nanocrystalline SnO2 thin films annealed in air

Tin oxide (SnO₂) thin films (about 200 nm thick) have been deposited by electron beam evaporation followed by annealing in air at 350-550 °C for two hours. Optical, electrical and structural properties were studied as a function of annealing temperature. The as-deposited film is amorphous, while all other annealed films are crystalline (having tetragonal structure). XRD suggest that the films are composed of nanoparticles of 5-10 nm. Raman analysis and optical measurements suggest quantum confinement effects that are enhanced with annealing temperature. For instance, Raman peaks of the as-deposited films are blue-shifted as compared to those for bulk SnO₂. Blue shift becomes more pronounced with annealing temperature. Optical band gap energy of amorphous SnO₂ film is 3.61 eV, which increases to about 4.22 eV after crystallization. Two orders of magnitude decrease in resistivity is observed after annealing at 350-400 °C due to structural ordering and crystallization. The resistivity, however, increases slightly with annealing temperature above 400 °C, possibly due to improvement in stoichiometry and associated decrease in charge carrier density.     

Stage III-recovery of cold worked high-purity aluminium determined with a low-temperature calorimeter

Using a low-temperature calorimeter annealing effects were investigated in high-purity aluminium of varying grades of purity (Al 99.99, Al 99.999 and Al 99.9999) which had been subjected to deformation by torsion at liquid nitrogen. For the purpose of comparison, some residual resistivity measurements were performed on deformed and quenched Al 99.999.The calorimetric signals comprises two consecutive peaks (low-temperature peak and high-temperature peak) for each degree of deformation and purity. The low-temperature peak, with a maximum at 200 K-210 K, lies in the temperature range stage III, well-known from isochronous resistivity measurements. The effective activation energy of the annealing defects in this peak has the valueQ _m=0.62 eV/atom averaged over all degrees of deformation and purity, and is thus close to the known values of the activation energy of vacancy migration. Throughout the high-temperature peak, the position of which on the temperature scale depends strongly on the degree of deformation and purity, the processes of primaty recrystallization and dislocation recovery take place in the material. The coincidence of this peak with the changes of mechanical and electrical properties are in accordance with this interpretation. Thus to the usual nomenclature for isochronous resistance measurements, one may designate this peak a stage V reaction peak.In this paper the particular results of the low-temperature peak (stage III peak) are analysed and discussed. Then the experimental data are compared with the literature data derived from other measuring procedures.     

Influence of copper intercalation on the resistive state of compounds in the Cu-HfSe<Subscript>2</Subscript> system

Polycrystalline samples of intercalated compounds Cu _x HfSe₂ have been synthesized for the first time and their electrical resistivity has been measured at both direct current and alternating current (with a frequency ranging from 200 Hz to 150 kHz) in the temperature range 80–300 K. It has been shown that the intercalation of copper atoms between three-layer Se-Hf-Se blocks leads to an increase in the electrical resistivity of the samples, as well as to a more pronounced activated character of the temperature dependence of the electrical resistivity. A time dependence of the electrical resistivity of the Cu _x HfSe₂ samples at room temperature, which is associated with the presence of copper ions in the sample, has been determined.     

Critical properties of nitrobenzene solutions by electric conductivity method

Electric conductivity of nitrobenzene soluted inn-hexane,n-heptane andn-octane was studied in constant and alternative field. Phase coexistence curves were determined together with the critical temperature, critical concentration and critical exponentβ for each of the systems. The measurements were performed in the temperature rangeT _s <T < (T _s + 10)K and for the concentrations of nitrobenzene between 0·2 ≲x ₂ ≲ 0·7 molar fraction.     

Temperature dependence of the electrical resistivity and the anisotropic magnetoresistance (AMR) of electrodeposited Ni-Co alloys

The electrical resistivity and the anisotropic magnetoresistance (AMR) was investigated for Ni-Co alloys at and below room temperature. The Ni-Co alloy layers having a thickness of about 2 μm were prepared by electrodeposition on Si wafers with evaporated Cr and Cu underlayers. The alloy composition was varied in the whole concentration range by varying the ratio of Ni-sulfate and Co-sulfate in the electrolyte. The Ni-Co alloy deposits were investigated first in the as-deposited state on the substrates and then, by mechanically stripping them from the substrates, as self-supporting layers both without and after annealing. According to an X-ray diffraction study, a strongly textured face-centered cubic (fcc) structure was formed in the as-deposited state with an average grain size of about 10 nm. Upon annealing, the crystal structure was retained whereas the grain size increased by a factor of 3 to 5, depending on alloy composition. The zero-field resistivity decreased strongly by annealing due to the increased grain size. The annealing hardly changed the AMR below 50 at.% Co but strongly decreased it above this concentration. The composition dependence of the resistivity and the AMR of the annealed Ni-Co alloy deposits was in good quantitative agreement with the available literature data both at 13 K and at room temperature. Both transport parameters were found to exhibit a pronounced maximum in the composition range between 20 and 30 at.% Co and the data of the Ni-Co alloys fitted well to the limiting values of the pure component metals (fcc-Ni and fcc-Co). The only theoretical calculation reported formerly on fcc Ni-Co alloys yielded at T = 0 K a resistivity value smaller by a factor of 5 and an AMR value larger by a factor of about 2 than the corresponding low-temperature experimental data, although the theoretical study properly reproduced the composition dependence of both quantities.     

Zum Einfluß der Versetzungsdichte auf die Primärrekristallisation von Kupfer und Silber nach extrem hoher plastischer Verformung

The isochronal and isothermal recovery of the electrical resistivity after large homogeneous compression of copper and silver was measured with a low frequency eddy current method. Two relations between the recovery data and the flow stress were found: 1. For high purity copper and silver the recovery of the electrical resistivity with recrystallization is proportional to the square of the flow stress. 2. The temperature at which half of the resistivity decrease with recrystallization is reached may be related to the flow stressσ by the equation \(\sigma ^2 e^{ - a/T_R } = const\) . The present experiments indicate that a simple relation between the quantitya and the activation energy for recrystallization cannot be given.     

Heat treatment effects on the structural and electrical properties of thermally deposited AgIn5S8 thin films

The heat treatment effects on structural and electrical properties of thermally deposited AgIn₅S₈ thin films have been investigated. By increasing the annealing temperature of the sample from 450 to 500 K, we observed a change in the crystallization direction from (420) to (311). Further annealing of the AgIn₅S₈ films at 550, 600 and 650 K resulted in larger grain size in the (311) preferred direction. The room temperature electrical resistivity, Hall coefficient and Hall mobility were significantly influenced by higher annealing temperatures. Three impurity levels at 230, 150, and 78 meV were detected for samples annealed at 350 K. The electrical resistivity decreased by four orders of magnitude when the sample annealing temperature was raised from 350 to 450 K. The temperature dependent electrical resistivity and carrier concentration of the thin film samples were studied in the temperature ranges of 25-300 K and 140-300 K, respectively. A degenerate-nondegenerate semiconductor transition at approximately 180 was observed for samples annealed at 450 and 500 K. Similar type of transition was observed at 240 K for samples annealed at 600 and 650 K.     

Recovery of electrical resistivity in amorphous pdsi alloys after low temperature neutron irradiation

Measurements of electrical resistivity after low temperature fast neutron irradiation are made for amorphous Pd₈₀Si₂₀ and Pd₈₀Ni₂Sl₁₈ and then Pd₈₀Si₂₀ annealed at 230°C and 360°C, and the isochronal annealing curves are obtained. The resistivity increase of Pd₈₀Si₂₀ annealed at 360°C is about 10 times larger than that of amorphous alloys and no defined annealing stage is observed in amorphous alloys and Pd₈₀Si₂₀ annealed at 360°C. For amorphous Pd₈₀Si₂₀, about 60% of the resistivity increase by irradiation remains after annealing up to room temperature and these are discussed by the structural relaxation.     

A sonochemical-assisted synthesis and annealing temperature effect of La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> nanoparticles

This paper reports on the sonochemical-assisted synthesis of La_0.7Sr_0.3MnO₃ (LSMO) nanoparticles (NPs) which have a single-crystalline perovskite structure. The average particle size of LSMO NPs was controlled from about 40 to 120 nm by changing the annealing temperatures from 750 to 1050°C. The particle size, electrical resistivity, and ferromagnetic transition temperature of LSMO NPs were strongly dependent on the annealing temperature. A substantial decrease in resistivity and an enhancement in the insulator–metal transition temperature were found on increasing the annealing temperature. Furthermore, the enhancement in magnetization and paramagnetic–ferromagnetic (PM–FM) transition temperatures was observed as the annealing temperature increases.     

Effects of processing on the electrical and structural properties of spray deposited CdS:In thin films

Polycrystalline CdS:In thin films were prepared by the Spray pyrolysis technique (SP) at a substrate temperature T_s=490 °C. The effects of annealing in nitrogen atmosphere at 400 °C and HCl-etching on the electrical and structural properties of the films were investigated. The electrical properties were studied through the analysis of the I-V curves, while the structural properties were studied through the analysis of the X-ray diffraction (XRD) patterns and the scanning electron microscope (SEM) images. An increase in the films’ resistivity was occurred after annealing and/or HCl-etching, which was accompanied by changes in the XRD patterns and SEM images. These changes were related to a phase change from the mixed (cubic and hexagonal) phase to the hexagonal phase which was expected to occur during the aforementioned processes. The X-ray diffraction (XRD) patterns and the scanning electron microscope images confirm this expectation.     

Electrical resistance,compressional strength,and extension of Ni-Mo and Ni-W alloys

An experimental study has been made of the temperature dependences of the compressional strength of Ni alloys with 5 and 10 at.% Mo and 5 at.% W, of the kinetic curves for the electrical resistance during annealing at 400 °C, and of the nature of the tensile deformation at various temperatures. The mechanism primarily responsible for the anomalous behavior of the temperature-rate dependence of the strength of these alloys may be the formation of microscopic carbide inclusions and Cottrell carbon atmospheres at dislocations during the deformation. Presence of the K state amplifies the jumps on the flow curves.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 1, pp. 89–93, January, 1970.In conclusion we note that this strengthening is displayed to some extent in other systems characterized by a K state.     

Synchrotron study of oxygen depletion in a Bi‐2212 whisker annealed at 363 K

Direct evidence is reported of structural and electronic effects induced on a single Bi₂Sr₂CaCu₂O_8+δ (Bi‐2212) whisker during a progressive annealing process. The crystal was investigated by micro X‐ray diffraction (µ‐XRD), micro X‐ray fluorescence and electrical characterization at the European Synchrotron Radiation Facility, during a series of three in situ thermal processes at 363 K. Each step increased the sample resistivity and decreased its critical temperature, up to a semiconducting behaviour. These data correlate with µ‐XRD analysis, which shows an increase of the c‐axis parameter from 30.56 Å to 30.75 Å, indicating an oxygen depletion mechanism. Mild temperature annealing could be an effective process to modulate the intrinsic Josephson junctions' characteristics in Bi‐2212 whiskers.     

Resistivity changes in cold-worked Cd-Mg and Cd-Sn

Experiments on Cd, Cd-0·12 at % Mg, Cd-0·48 at % Mg, Cd-0·056 at % Sn and Cd-0·18 at % Sn wires deformed by torsion in liquid nitrogen have shown that up to 200 K (where in Cd the polygonization and/or recrystallization starts) the form of the isochronous annealing spectrum of electrical resistivity remains unchanged irrespective of the degree of deformation and impurity content. For the Cd-Sn alloy this is in contrast with recent experiments on quenched specimens. It seems at present that this discrepancy is due to the inherent difference of the behaviour of lattice defects in cold-worked and quenched specimens.     

The apparition of a new reaction at lower temperature in equiatomic CuAu alloy

Recently a lot of interest has been devoted to the study of order–disorder transitions in different materials. Although the equiatomic CuAu alloy represents a classical model of this type of transformation, it still receives considerable attention because many questions about phase transitions are still raised according to its equilibrium diagram. In this context, the present paper carries a new result observed in CuAu alloy consisting of a new anomaly observed on differential scanning calorimetry (DSC) curves at low temperature and new peaks in X-ray diffraction (XRD) spectra. For that, we will try to give an explanation of the origin of this new reaction, with the help of other techniques as electrical resistivity and microhardness measurements. The kinetic behaviour of this new reaction has been also studied by anisothermal analysis during DSC tests to estimate the kinetics parameters as activation energy E _act and Avrami exponent n.