Regularities of Structure Formation in 30 mm Rods of Thermoelectric Material during Hot Extrusion

In this study, Ingots of (Bi, Sb)2Te3 thermoelectric material with p-type conductivity have been obtained by hot extrusion. The main regularities of hot extrusion of 30 mm rods have been analyzed with the aid of a mathematical simulation on the basis of the joint use of elastic-plastic body approximations. The phase composition, texture and microstructure of the (Bi, Sb)2Te3 solid solutions have been studied using X-ray diffraction and scanning electron microscopy. The thermoelectric properties have been studied using the Harman method. We show that extrusion through a 30 mm diameter die produces a homogeneous strain. The extruded specimens exhibit a fine-grained structure and a clear axial texture in which the cleavage planes are parallel to the extrusion axis. The quantity of defects in the grains of the (Bi, Sb)2Te3 thermoelectric material decreases with an increase in the extrusion rate. An increase in the extrusion temperature leads to a decrease in the Seebeck coefficient and an increase in the electrical conductivity. The specimens extruded at 450 °C and a 0.5 mm/min extrusion rate have the highest thermoelectric figure of merit (Z = 3.2 × 10−3 K−1).

Determining the Preferred Orientation of Silver-Plating via X-ray Diffraction Profile

Determining the preferred orientation of plating film is of practical importance. In this work, the Rietveld method and quantitative texture analysis (RM+QTA) are used to analyze the preferred orientation of plating silver film with XRD profile, whose <311> axial texture can be completely described by a set of exponential harmonics index, extracted from a single XRD profile, C41,1(0.609), C61,1(0.278), C81,1(−0.970). The constructed pole figures with the index of the exponential harmonic are following those measured by the multi-axis diffractometer. The method using exponential harmonic index can be extended to characterize the plating by electroplating in a quantitative harmonic description. In addition, a new dimension involving crystallite shape and size is considered in characterizing the preferred orientation.

Use of a Be-dome holder for texture and strain characterization of Li metal thin films via sin2(ψ) methodology

Residual strain in electrodeposited Li films may affect safety and performance in Li metal battery anodes, so it is important to understand how to detect residual strain in electrodeposited Li and the conditions under which it arises. To explore this Li films, electrodeposited onto Cu metal substrates, were prepared under an applied pressure of either 10 or 1000 kPa and subsequently tested for the presence or absence of residual strain via sin2(ψ) analysis. X-ray diffraction (XRD) analysis of Li films required preparation and examination within an inert environment; hence, a Be-dome sample holder was employed during XRD characterization. Results show that the Li film grown under 1000 kPa displayed a detectable presence of in-plane compressive strain (−0.066%), whereas the Li film grown under 10 kPa displayed no detectable in-plane strain. The underlying Cu substrate revealed an in-plane residual strain near zero. Texture analysis via pole figure determination was also performed for both Li and Cu and revealed a mild fiber texture for Li metal and a strong bi-axial texture of the Cu substrate. Experimental details concerning sample preparation, alignment, and analysis of the particularly air-sensitive Li films have also been detailed. This work shows that Li metal exhibits residual strain when electrodeposited under compressive stress and that XRD can be used to quantify that strain.

Applicability of Measurements of Local Electrical Parameters in the Modeling of Technological Texture of Ceramic Blanks

The paper deals with the modeling of the technological texture of the pressed ceramic materials in the radial and axial direction, which consists in the graphical representation and subsequent analysis of the distribution of the electrostatic field potential differences on the surface of the dielectric sample with the diameter d and the thickness h located between the electrodes. In occasion of observing radial texture the electrodes have the cylindrical configuration and in occasion of observing the axial texture in the sample the electrodes have the axial configuration. The theoretical relationship in the paper is derived for the calculation of the voltage values measured at any position between the center electrode and the peripheral electrode, at a constant voltage U applied to the outer and inner electrodes of the dielectric sample of thickness h of the raw ceramic sample material (radial texture). Measurements have demonstrated the suitability of identifying the technological texture by measuring the potential differences on the sample surface which is located between the electrodes in the relation to the technology preparation and to the quality of the fired ceramic production.

Микрофазовое разделение в имидсилоксановом сополимере

By means of electron microscopy, a comparative analysis of the micro-inhomogeneous structure of the surface of films of amorphous aromatic polyetherimide — poly{4,4'-bis[(4''-N-phenoxy) diphenylsulfone] imide 1,3-bis (3',4-dicarboxyphenoxy) benzene} (PEI) - and imidosiloxane block copolymer (PSI) containing blocks of PEI units and blocks of dimethylsiloxane units. It is shown that in the PSI film, compared with PEI, the anisotropy, long-range order, and the correlation length of density fluctuations increase. The PSI sample has an asymmetrical biaxial surface texture, unlike PEI, which is characterized by an axial texture. In the direction of the axes of the PSI texture on a micron scale, periodic density oscillations are observed. The results obtained indicate microphase separation in the PSI film due to spatially oriented contact interactions between the blocks of dimethylsiloxane units.

Electroplastic effect in metals

A mechanism of electroplastic effect considered as well as possible areas of its technological application during rolling, drawing, stamping of thin sheets and other methods of metals forming.A conception justified that metal electroplastic deformation, based on electroplastic effect, can be applied at middle and final metallurgical stage. Electroplastic effect allows to decrease metal resistance to deformation by 25–30% and increase the ductility of a metal during its forming, to increase residual ductility till 30%. Due to increasing of axial texture perfection degree of wire during drawing technology with electroplastic effect application, a decrease of its electric resistance by 15% is reached. During the metal electroplastic deformation of stainless steels the austenite-martensitic phase γ→α transformation is practically completely suppressed, which makes unnecessary operations of money-and energy consuming austenizating annealing.Based on electroplastic effect about 45 mills and powerful metal-processing facilities, using metal electroplastic effect deformation created in different countries (mainly in Russia, South Korea, Italy, Great Britain and China). Different variants of effective energy-saving critical technologies are being developed by metal electroplastic effect deformation by rolling, drawing, stamping and flatting, as well as briquetting of metal wastes with current. A new equipment is created and existing equipment is modernized for application of metal еlectroplastic effect deformation technology.

Effect of Turning and Surface Polishing Treatments on Surface Integrity and Fatigue Performance of Nickel-Based Alloy GH4169

In this paper, the effects of turning and surface polishing treatments on surface integrity and fatigue properties of superalloy GH4169 were investigated. Finish turning (FT), surface circumferential polishing treatment (TCP), surface oblique texture (TCPO), and surface axial texture (TCPA) were applied to GH4169 superalloy. The surface roughness, surface topography, residual stress, microhardness, and microstructure after different processes were studied. Rotating bending fatigue tests were carried out to investigate the effects of surface integrity and surface texture direction on the fatigue performance of GH4169. The experiments reveal that the TCPA specimens present the longest fatigue life of 15.01 × 104 cycles. By comparison with the FT, TCP, and TCPO specimens, the fatigue lives of TCPA specimens are increased by 134.2%, 183.7%, and 96.2%, respectively. Single crack initiation source is observed for TCPA specimen. It is mainly attributed to the small surface stress concentration factor and surface axial texture.

The Structure and Shape Memory of the Hot Extruded NiTi Alloy

The paper presents results of structural studies of hot extruded NiTi shape memory alloy that is in the B2 phase at room temperature. Texture of the alloy was determined from the X-ray diffraction measurements. It was found that in result of 60 % sample reduction (at a cross-section of a bar formed by hot extrusion) weak axial texture - type <110>B2 was formed. The volume of the grains oriented in this way was approx. 20 %. Basing on metallographic observations it was also found that the size of the grains formed as a result of the thermomechanical treatment was uniform with the average area of 1700 μm2. This information is significant from the point of view of functional properties. Hot extruded alloy revealed presence of the reversible martensitic transformation. Its characteristic temperatures were slight higher than in as-cast alloy. Moreover, the extruded NiTi alloy showed 100 % of the shape recovery.

Giant Young’S Modulus Variations in Ultrafine-Grained Copper Caused by Texture Changes at Post-Spd Heat Treatment / Gigantyczne Zmiany Modułu Younga W Ultra Drobnoziarnistej Miedzi Spowodowane Przez Zmiany Tekstury W Trakcie Obróbki Cieplnej Po SPD

The effect of annealing on dynamic Young’s modulus, E, of ultrafine-grained (UFG) copper obtained by combined severe plastic deformation (SPD) is investigated. It is established that Young’s modulus in the SPD-prepared samples exceeds that in the coarse-grained fully annealed (CGFA) samples by 10 to 20 %. Isothermal annealing at elevated temperatures between 90 and 630°С leads to a sharp decrease of Young’s modulus for annealing temperatures above 210°С. After annealing at 410°С, the value of E reaches its minimal value that is 35 % lower than E in CGFA samples (total change in E is about 47 % of the initial value). Further annealing at higher temperatures leads to an increase in Young’s modulus. It is shown, that the unusual behavior of Young’s modulus is caused by formation of the <111> axial texture in the SPD-treated samples which then is replaced by the <001> texture during the post-SPD heat treatment.