This study deals with the influence of the rolling asymmetry and applied strain on the crystallographic texture of polycrystalline copper. It was shown that textures of asymmetrically rolled materials are rotated with respect to those rolled symmetrically and the rotation angle increases both with the rolling asymmetry and strain. The asymmetric rolling leads also to a decrease of intensity of texture components forming skeleton lines in the orientation space. However, individual texture components exhibit different sensitivity to the effect of asymmetric rolling.
The main goal of this work is to establish the influence of annealing on the properties of Cz-Si wafers previously subjected to the hydrogen ion-beam treatment at 25 or 300-350°C. It is demonstrated by the conducted study that, despite similarity in the effects of the hydrogen ion-beam treatment at different temperatures on some electrical properties of the wafers (photovoltage spectra, thermoelectromotive force sign), thermal stability of changes in these properties due to the hydrogen ion-beam treatment depends on the hydrogenation temperature.
The increases in strain hardening observed for the in-plane tensile deformation of well-aged magnesium alloy AZ31 are related to a transition from basal to non-basal slip. Based on the results of texture measurements, the double prismatic slip is proposed as the dominant secondary mechanism. The necessary fast strengthening of the basal slip is modelled by an accommodation contribution to the grain boundary resistance. The transition may be consistently modelled by involving the accommodation rather than the production of new sessile dislocations into the evolution laws for dislocation populations.
In order to improve soft magnetic properties of vacuum degassed NO steels, an adjusted temper rolling process for development of particular textures {100}<0vw> was used. The main idea here relies on a deformation-induced grain growth, which promotes preferable formation of the grains with desired orientation. Two vacuum degassed NO steels were chosen as an experimental material. In both cases, a coarse or columnar grained microstructure, with pronounced intensity of cube and Goss texture components, was achieved during a continuous final annealing. The obtained microstructure leads to a significant decrease of coercivity, measured in DC magnetic field. The coercivity of steel with silicon content 2.4 wt.% decreased from 42 A/m to 17 A/m. Even more remarkable improvement of the soft magnetic properties was observed for the steel with Si 0.6 wt.%, where the coercivity value dropped from 68 A/m to 12.7 A/m.
Non grain oriented isotropic electrical steels, commercially called NGOES, were investigated in cryogenic temperature conditions. At cryogenic temperatures plastic deformations form strong structural heterogeneities in the sample thickness. Samples processed by cryo rolling show a bigger storage energy. To achieve abnormal grain growth through the process of static recrystallization, the annealing conditions were applied to the deformed samples. Moreover, minimal magnetic losses were reached when mean grain size diameter was approximately 150 μm.
Theγ-γ perturbed angular correlation technique is a very powerful tool for the investigation of dopant incorporation and damage recovery after implantation in semiconductors. The basic principles of the technique will be introduced followed by a discussion of its strengths and limitations. Examples of its application will be given, ranging from cavities in silicon, effects of uniaxial stress on acceptor-donor pairs in silicon to damage recovery in nitride semiconductors like GaN.
Fabrication of a Ti₂AlN MAX phase for contact applications to GaN-based devices is reported. Sample characterisation was done by means of X-ray diffraction and secondary ion mass spectroscopy. Successful Ti₂AlN monocrystalline growth was observed on GaN and Al₂O₃ substrates by annealing sputter-deposited Ti, Al and TiN layers in Ar flow at 600°C. The phase was not seen to grow when the layers were deposited on Si (111) or when the first layer on the substrate was TiN. N-type GaN samples with Ti₂AlN layers showed ohmic behaviour with contact resistivities in the range 10¯⁴ Ωcm².
Due to unique features, like shape memory effects and superelasticity, NiTi alloys with nearly equiatomic composition are used in various branches of industry. Application of severe plastic deformation can drastically change properties of the materials. In the present paper the Ni_{50.4}Ti_{49.6} alloy after cold rolling in the martensitic state and further annealed is studied. Phase transformations were studied using X-ray diffraction and differential scanning calorimetry measurements. Microstructure was examined using transmission electron microscopy and electron backscattering diffraction methods. Mechanical properties of obtained alloys has been studied using Vickers microhardness tests. Based on the performed measurements it can be seen that in studied alloys two steps B2 ↔ R ↔ B19' phase transitions occurred. Performed plastic deformation influences course of phase transitions and phases composition. Due to the reduction of grain size microhardness of the studied material is increasing with increase of deformation degree.
The aim of this study was to reveal the influence of the heat treatment after welding of 17-7PH (X7CrNiAl17-7) steel on the microstructure evolution and the texture of the welds. Microstructure investigation carried out by light microscopy and transmission electron microscopy showed that the austenite and δ ferrite coexist in as-welded condition. Annealing at the temperature range between 400°C and 620°C after welding causes small changes in the microstructure and the hardness of the welds increases. Heat treatment at 760°C for 1 h resulted in the partial destabilization of the austenite. Aging after destabilization leads to tempering of the martensite: first the hardness increases and then decreases. The maximum hardness is observed when the ageing temperature reaches 510°C. XRD studies confirmed the presence of the two phases: δ ferrite and austenite. Annealing at 400°C/1 h and 550°C/1 h results in changes of the intensities for individual peaks derived from austenite and ferrite. The calculated ratios of peak intensity were compared with the intensities of the reference sample. The differences in intensities suggested strong texture of the material.
The present work deals with the texture and microstructure development in high-manganese steel X85MnAl29-9. It was cold rolled to 50% reduction and then aged at 550°C for various times. The investigations included measurements of texture, X-ray phase analysis and microstructure observations. The results indicate that, when ageing takes place, precipitation of κ' carbide in an austenitic matrix and carbide κ at grain boundaries occur. The existence of satellites suggests that (Fe, Mn)₃AlC carbides were formed within the austenite matrix by spinodal decomposition.
Studies on the use of energetic ion beams for material modification have been initiated originally within the Manhattan project and have been continuously developed since then. The consecutive steps were devoted to the studies of ion implantation into semiconductors, metals, ceramics and, most recently, organic materials. One of the latest areas of applications is modification of elastomers, commonly known as rubbers. In the present paper the results of the studies on structural and functional properties of irradiated elastomers will be presented with the special emphasis on the materials used in aviation and military applications. Among the structural modifications, a massive loss of hydrogen atoms appears as the most peculiar characteristic of irradiated elastomers. Functional properties of irradiated rubbers: microhardness and friction coefficient, will be presented and application potential of the materials discussed.
In this study, the solid particle erosion behavior of solutionized, artificially aged (T6) and annealed aluminum alloy AA7075 has been investigated. The samples were eroded in solid particle erosion test equipment at 45° impingement angle and 75 m/s impingement velocity with 180 mesh garnet erodent particles. Afterwards, microstructures of solutionized, artificially aged and annealed samples of AA7075 alloy were analyzed. In order to figure out the effect of ductility on erosion rates, the Brinell hardness of the samples was measured. The surface morphology images of the samples were taken before and after the erosion test by using scanning electron microscope (SEM). The effects of the microstructures and the hardness on the erosion behavior of the different heat treated specimens were examined. Finally, SEM images of the samples were deeply analyzed and the erosion mechanisms which occurred on the surfaces of the samples were discussed.
Advanced engineering materials are frequently based on multiphase microstructures, where the decisive step is the heat treatment adjusting the desired microstructure. A typical example are transformation-induced plasticity assisted steels, where the steel grades depend on the phase composition and the deformation-induced transformation of retained austenite into martensite. Usually methods for microstructural characterization are only applied after completion of the heat treatment process and comprise typically microscopy and X-ray analysis with laboratory tubes. Both methods can suffer from artefacts and probe a relatively small surface or volume, respectively. However, in the last decade synchrotron facilities have become available that offer very hard X-rays, which open up new possibilities for the observation of heat treatment processes owing to the unique combination of extremely high intensities with large penetration depths (mm scale). Sophisticated sample environments allow for complex in situ experiments, currently with a time resolution on the order of seconds. Only recently a commercial dilatometer of type Bähr Dil805AD has become available at the HARWI-2 beamline at the HASYLAB. This experimental setup was used for the in situ investigation of the quenching and partitioning process in transformation-induced plasticity steels. The experiments were performed in transmission at a wavelength of 0.0124 nm. The Debye-Scherrer rings were observed arising from statistical grain distributions characteristic for each microstructure. The time-resolved measurements allow conclusions about the phases present in the sample, their lattice parameters, texture and grain size.
This paper presents the investigations of electrical properties and effect of annealing on conductivity of (CoFeZr)_{x}(CaF_2)_{100-x} nanocomposites produced by ion-beam sputtering in the Ar and O_2 ambient. Investigations into conductivity of (CoFeZr)_{x}(CaF_2)_{100-x} nanocomposites depending on the measuring temperature and the annealing temperature have been performed. The application of a combined argon-oxygen beam brings about lowering of the potential barrier on the surface of nanoparticles. In the course of annealing the additional oxidation occurs. First it proceeds on the surface and then all through the metallic-phase particles.
This paper presents the investigations of the electrical properties of the (CoFeZr)_{x}(PZT)_{1-x} nanocomposite with the metallic phase content x=43.8 at.%, which was produced by ion beam sputtering. Such preparation took place under an argon atmosphere with low oxygen content with its partial pressure P_{O₂} = 2×10¯³ Pa. The measurements were performed using alternating current within the frequency range of 50 Hz-10⁵ Hz for measuring temperatures ranging from 238 K to 328 K. The (CoFeZr)_{43.8}(PZT)_{56.2} nanocomposite sample subjected to a 15 min annealing process in air at the temperature Tₐ=423 K demonstrates a phase angle of -90° ≤ θ ≤ 0° in the frequency range 50 Hz-10⁵ Hz. It corresponds to the capacitive type of conduction. In the frequency range 10⁴-10⁵ Hz sharp minima in selected conductivity vs. frequency characteristics occur, which corresponds to a current resonance phenomenon in RLC circuits. In case of a sample annealed at Tₐ=498 K the inductive type of conduction with 0° ≤ θ ≤ +90° occurs in a high frequency area. At the frequency f_{r} characterized by the phase angle θ = 0°, the capacity value reaches its local minimum. It indicates a voltage resonance phenomenon in conventional RLC circuits. The θ = +90° crossing in the frequency dependence of phase angle corresponds to the current resonance phenomenon, which is represented by a strong local minimum in the conductivity vs. frequency characteristics.
Microstructure and texture of the friction stir welded 5083 and 7075 aluminum alloys were characterized by means of the electron backscatter diffraction and X-ray techniques. A complex vortex-like microstructure with distinctive bands of the both joint materials was found in the centre of the weld. The alternating bands filled roughly equiaxed dynamically recrystallized grain volumes. The grain size was slightly smaller in bands of the alloy 7075 than in bands of the alloy 5083. Grains in the thermomechanically affected zone were elongated, especially on the retreating side of the weld (7075 alloy). On the other hand, the grain shape in the heat affected zone was similar to that for the base material.
Positron annihilation characteristics as a function of composition and annealing in zinc vapour were measured and compared with photoluminescence spectra for Zn_{1-x}Mg_{x}Se mixed crystals with 0 ≤ x ≤ 0.6. The positron annihilation data show that there is a substantial number of divacancies present in the system under study. The concentration of such defects is reduced at least by the factor of two upon annealing in zinc vapour.
Magnesium single crystals of purity (99.8 wt%) deformed to stage B on the work-hardening curve at the temperature of 293 K and at a strain rate of 10^{-3} s^{-1} were investigated. The modified Bridgman method was used to obtain the crystals of the preferred orientation of (0001)〈11\overline{2}0〉 as primary slip system. By using the method based on the experimental gradient matrix, the activity of slip systems was obtained in magnesium single crystals deformed to shear strain 1.2 γ, where well developed stage B of work hardening was observed. It was shown that primary (0001)〈11\overline{2}0〉 slip system was dominant in the whole investigated range of the examined deformation. The observation and analysis of etch pits on the {\overline{1}2\overline{1}0} plane showed the heterogeneous distribution of dislocations formed during deformation into walls of dislocations perpendicular to the (0001) slip plane. The suggested model of work hardening of magnesium single crystals, which is worth taking into consideration, shows the influence of the long-range stress field derivating from the groups of dislocations arranged in dislocation walls.
The Co_{38}Ni_{33}Al_{29} alloy in both powder and bulk state was investigated in the presented study using neutron diffraction on E9 high resolution powder diffractometer at HZB (BER II). The reverse martensitic phase transformation from the tetragonal martensitic phase into the cubic austenitic phase was observed with the phase coexistence within the temperatures from 183 K to 133 K. The fcc cobalt solid solution particles distributed in the transforming matrix remained in the same state through the whole temperature range. The obtained results agree with magnetization measurements on the same annealed sample. The powder data are compared with experiments on bulk sample, although there was a texture present. The obtained results provide further information about the phase transition process in this important class of ferromagnetic shape memory alloys.
Composite multilayer sheets from Al/AlMg3 with 32 alternating layers of Al and AlMg3 were prepared by accumulative roll-bonding and their thermal stability was studied. Recrystallized 2 mm thick sheets of a commercial twin-roll cast AlMg3 alloy and high purity Al99.99 served as input materials. Electrical resistivity measurements were used for the integral monitoring of solute atoms distribution during annealing. Light optical microscopy was employed for the direct grain-size determination and recrystallization description. Post-mortem electron microscopy observations were performed on as-prepared and annealed specimens and they were combined with in situ heating electron microscopy in order to explain the observed annealing effects. A broadening of Al layers during annealing was observed and related to diffusion of magnesium.
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