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To build thermoelectric generators, leg materials with a high figure of merit, ZT, are essential. Skutterudites are promising candidates because besides being environmentally friendly, the starting material is available and cheap and they can be used in a wide temperature range. To enhance ZT, severe plastic deformation via high-pressure torsion, HPT, was successfully applied on ball-milled and hot-pressed skutterudites as well as to directly densify skutterudite powder. Severe plastic deformation introduces many defects, mainly dislocations, into the sample and in parallel the crystallite size is significantly reduced. During measurement-induced heating these defects anneal partially out, and the grains grow. It was observed that while heating HPT processed material from room temperature to about 850 K, changes of the temperature-dependent physical properties, most of all the electrical resistivity, the density, and the thermal expansion occur more or less simultaneously around 600 K. For the first time we have combined in situ TEM observations as well as in situ measurements of the elastic modulus and hardness in order to get a deeper insight into the microstructural behavior of a p-type skutterudite, DD 0.7 Fe 3 CoSb 12 (DD = didymium) during increasing temperature from 300 K to 823 K. HPT-DD 0.7 Fe 3 CoSb 12 is a high quality thermoelectric material with 1.2 < ZT < 1.4 at 750 K (hot-pressed reference sample: ZT ∼ 1.2 at 810 K). [Display omitted] • High-pressure torsion severely influences electrical/thermal resistivity. • Anomalies in electrical resistivity are reflected in hardness, Young's modulus. • performed in-situ measurements of Young's modulus, hardness, TEM, HRTEM. • Severe lattice disorder responsible for anomalies. • Microstructure-changes after high pressure torsion boost thermoelectric properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile fabrication of micron-sized nanostructured ε-phase Mn-Al particulates by end-milling. • These ε-phase particulates are suitable for preparation of τ-phase particulates with promising permanent magnet properties. • Retention of sub-micrometer grain size τ-phase after isothermal annealing of the ε-phase particulates. • New method with reduced number of processing steps for particulate-based fabrication of τ-phase Mn-Al permanent magnets. We utilize the plastic deformation process associated with the machining operation of end-milling for the preparation of ε-phase Mn-Al particulates with micron scale external dimensions and self-similar shapes from binary as-cast feedstock with composition 54 at.% Mn and 46 at.% Al. The structural evolution and development of magnetic properties in response to the single-pass plastic deformation processing by the end-milling and subsequent thermal annealing have been studied. Effects of end-milling process parameter combinations, primarily the rotational speed of the cutting tool, have been identified to permit genesis of morphological self-similar particulates of ε-phase characterized by cold-worked and sub-micron to nanometer scale refined microstructures. The end-milling derived particulates were suitable for preparation of τ-phase based MnAl particulates with enhanced permanent magnet properties via isothermal annealing. Discernibly higher rates for the exothermic ε-phase decomposition reactions in the end-milling derived particulates have been observed for isothermal annealing at temperatures in the range of 673 K ≤ T ≤ 723 K. The enhanced decomposition reaction kinetics have been attributed to reduced effective nucleation barriers for the respective product phases stemming primarily from reduced grain size. Large saturation magnetization and coercivity in combination with reasonable squareness ratios of the magnetization curves resulted in a (BH) max = 4.2 MGOe for the end-milling derived binary Mn 54 Al 46 particulates obtained for the highest rotational tool speed of 4200 RPM used here after annealing for 20 min at 673 K. The ε-phase Mn-Al particulates derived by end-milling have potential as precursors for the fabrication of τ-phase Mn-Al based PM materials. [ABSTRACT FROM AUTHOR]

The Ga 2 O 3 (ZnO) m family of homologous compounds have been identified as potential thermoelectric materials, but properties are often limited due to low densification. By use of B 2 O 3 as an effective liquid phase sintering aid, high density, high quality ceramic samples of Ga 2 O 3 (ZnO) 9 have been synthesised. The atomic structure and local chemical composition of Ga 2 O 3 (ZnO) 9 have been determined by means of high resolution X-ray diffraction and atomic resolution STEM-HAADF, EDS and EELS measurements. X-ray analysis showed that the compound crystalizes in the Cmcm orthorhombic symmetry. Atomically resolved HAADF-STEM images unambiguously showed the presence of nano-sized, wedge-shaped twin boundaries, parallel to the b-axis. These nano-scale structural features were chemically investigated, for the first time, revealing the exact distributions of Zn and Ga; it was found that Ga ions occupy sites at the junction of twin boundaries and inversion boundaries. HAADF-EDS analysis showed that the calcination step has a significant impact on crystal structure homogeneity. By use of a sintering aid and optimization of processing parameters the ceramics achieved a low thermal conductivity of 1.5–2.2 W/m.K (for the temperature range 300–900 K), a power factor of 40–90 μW/K.m 2 , leading to a ZT of 0.06 at 900 K. The work shows a route to exploit nanoscale interface features to reduce the thermal conductivity and thereby enhance the thermoelectric figure of merit in complex thermoelectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Solvothermal synthesis of ZrO2–TiO2 binary oxides and pure counterparts at 150°C in water/isopropanol media is presented. Titanium (IV) isopropoxide and zirconium (IV) propoxide were used as precursors. XRD and TEM techniques were used for structural and morphological characterization of obtained samples. XPS spectra of mixed oxide samples were compared in order to correlate composition of samples with surface properties and presence of defects. Relative positions of defect states within band‐gaps of semiconductors were estimated from UCPL spectra. UV‐Vis DRS spectra revealed that both pure oxides experienced red shift of absorption thresholds compared to reference data. Photocatalytic activities of all samples were probed under simulated Solar light on three model compounds: phenol, 4‐chlorophenol (4‐CP) and 2, 4, 6‐trichlorphenol (TCP). Pure TiO2 showed the highest photocatalytic activity in the case of phenol. However, pure ZrO2 and binary oxides showed higher photoactivity in degradation of 4‐CP and TCP. The activity of wide band‐gap semiconductors under simulated Solar light in photodegradation of phenol and its derivatives is most probably the consequence of formation of charge transfer complexes between pollutant molecules and semiconductors surface. [ABSTRACT FROM AUTHOR]

This study examines the effects of titanium content on hydrogen embrittlement in hot-stamped boron steel, by employing an electrochemical cathodic charging method, slow rate tensile tests, and thermal desorption analyses. With increasing titanium content in hot-stamped boron steel, titanium carbides are precipitated, while the resistance to hydrogen embrittlement improves with a slight reduction in the elongation when stress is applied to the hydrogen-charged specimens. The specimens with a high titanium content exhibit a relatively superior resistance to hydrogen embrittlement due to the presence of small titanium carbide precipitates that act as irreversible hydrogen trap sites with a high binding energy. [ABSTRACT FROM AUTHOR]

The microstructure of a nickel-based single crystal superalloy has been investigated after creep deformation at 1033 K under stress up to 850 MPa. High density of stacking faults are formed in γ′ precipitates during the creep deformation. At 700 MPa and 850 MPa, bi-directional stacking faults are observed. These stacking faults are induced by the movement of a/3<112> partial dislocations. Two formation mechanisms of a/3<112> partial dislocations, reaction and dissociation mechanisms, are simultaneously observed in this alloy after deformation. The proportion of a/3<112> dislocations formed by the dissociation mechanism increases as the applied stress increases. The primary creep strain of this alloy is 2.45% at 850 MPa, which may be attributed to the combination of these two mechanisms. [ABSTRACT FROM AUTHOR]

We investigated the crystal structure and the martensitic transformation in equiatomic HfPd alloy. The analysis of the crystal structure by electron diffraction and Rietveld refinement using X-ray diffraction data indicates that the space group of the martensitic phase is Cmcm , and the lattice parameters are a = 0.329 nm, b = 1.021 nm, and c = 0.438 nm. Martensitic variants are composed of the plate-like morphology of several hundred nm, and the boundaries between the variants have (021) Cmcm twin relations. This (021) Cmcm twin boundary seems to be sharp without ledge and steps. Differential scanning calorimetry measurement indicates that each martensitic transformation temperature is determined to be M s = 819 K, M f = 794 K, A s = 928 K, and A f = 954 K. Based on the dimension change using a thermo-mechanical analyzer, the expansion and shrinkage of the sample occurred with the forward and reverse martensitic transformation, respectively. [ABSTRACT FROM AUTHOR]

In this study, 1 mm thick 6061-T6 aluminum alloy plates were subjected to friction stir spot welding (FSSW) at a very low rotation speed of 30, 40 and 50 rpm, aiming to prevent the hardness reduction in the heat affected zone (HAZ) of this precipitate hardening Al joints. Two kinds of rotating tools, namely, one with a 1 mm long probe and the other one with a flat shoulder without a probe, were used and the corresponding force applied to the rotating tools was ranged from 4 to 8 tons. Under this special welding condition, the highest welding temperature was measured lower than 200 °C. As a result, no hardness reduction of the HAZ region could be detected and an ultrafine grain structure with a high density of dislocations was formed in the stir zone. The average grain size obtained in the stir zone was less than 500 nm for all the welds, which was much smaller than that in conventional FSSW processed 6061-T6 Al joints. In addition, no hook-like bonding ligaments were formed in the joints due to the very different material flows and the shear tensile tests showed that the spot welds prepared by the low speed FSSW can reach a maximum shear load of about 5400 N, much higher than those prepared by the conventional FSSW technique. [ABSTRACT FROM AUTHOR]

The subtle change in the space group that occurs in the Al 12-x Mn x Ce τ phase as the Al/Mn ratio is varied in the Al-Mn-Ce system was characterized using scanning electron microscopy and analytical transmission electron microscopy and the atom positions associated with this change were refined using x-ray diffraction. In addition, the reaction temperatures were identified using differential scanning calorimetry. Understanding the nature of this phase is of particular importance because of its presence in a series of high strength, high temperature alloys that are being pursued in this system. It is shown that there are two distinct space groups for the τ phase that are related to one another and depend on the Al/Mn ratio – at lower ratio, the space group is I4//mmm but at higher Al/Mn ratio, the Mn and Al atoms order on one of the Wyckoff sites in the I 4/ mmm structure and the ordering plus slight distortions away from the symmetry positions causes a loss of the body centering and a change to the P 4/ nmm space group with a unit cell approximately twice that of the I 4/ mmm cell. The results provide clarification to the conflicting reports in the literature and lead to a clearer assessment of the phase equilibria in the Al-rich portion of the Al-Mn-Ce system. [ABSTRACT FROM AUTHOR]

Unexpected variations in the purity and structure of commercial detonation nanodiamonds (DNDs) is an ongoing issue. Unfortunately, influences of these variations and how they affect DND behaviors are seldom addressed. This work investigates nominally homologous commercial DNDs sold by a single vendor under the same item number but different lots. Paraffin wax and surfactant were discovered as the major organic contaminants in the DND samples along with metallic impurities. The relative quantities of these contaminants were correlated to discrepancies in the structure and crystallinity of DNDs. The DNDs containing more contaminants possessed thicker shells surrounding the diamond cores; the diamond crystallinity was observed to quickly disappear, on the order of several minutes, when exposed to 200 kV electron beam. On the other hand, those DNDs carrying fewer impurities exhibited a stable diamond structure. The differences in metallic impurities were attributed to variations in the DND purification treatments, and did not appear to affect a morphological change under the electron beam. The present work demonstrates the negative effects of impurities in commercial DNDs on the content and stability of diamond carbons. The results also have implications on possible factors that must be considered when using commercial DNDs for advanced applications. [ABSTRACT FROM AUTHOR]

Traditionally, magnetostriction of ferromagnetic materials was considered as an intrinsic homogeneous effect. More recently, the magnetostriction in certain binary systems such as Fe-Ga alloys, has been associated with nanoscale heterogeneities, but evidence of a direct relation between the heterogeneities and magnetostriction was lacking. Here heterogeneous magnetostriction controlled by nanoinclusions is reported in Fe-Co alloys, where the largest values are found in two-phase coexistence regions. Systematic investigation of the nanostructure-dependent magnetostriction in Fe-Co alloys using synchrotron X-ray diffraction and high-resolution TEM with geometric phase analysis has allowed us to identify the nature of the B2-like and fcc-like nanoinclusions that are responsible for the enhanced magnetostriction in this system. The relation between magnetostriction and the nanoheterogeneities is established by tailoring the nanoinclusion size with alloy composition and annealing temperature. This provides the direct experimental evidence of nanoinclusion-induced enhanced magnetostriction. Finally, a model is presented to explain how coherent inclusions with the ordered B2-like structure or fcc-like structure can induce tetragonal distortions of the matrix in the relevant two-phase regions and thus enhance the magnetostriction. The results clarify the magnetostriction mechanism and may stimulate a search for new magnetostrictive materials. [ABSTRACT FROM AUTHOR]

As an intrinsic materials property and an important criterion in structural design, the Young's modulus of cast aluminium alloys can be significantly increased through adding Si and Cu elements as well as in-situ forming Mg 2 Si and TiB 2 particles in the alloys to make castings with complex geometry. The microstructural evaluation and mechanical properties of Al Si Mg alloy and Al Si Mg Cu/Mg 2 Si TiB 2 hybrid composite were examined by X-ray diffractometer (XRD), optical microscopy (OM), scanning and high resolution transmission electron microscopes (SEM and HRTEM), ultrasonic pulse technique and tensile test. The results revealed that the Al Si Mg Cu/Mg 2 Si TiB 2 hybrid nanocomposite could provide the Young's modulus more than 94 GPa and the yield strength up to 235 MPa by forming the α-Al (Cu, Mg), Si, Mg 2 Si and TiB 2 phases in the microstructure. Micromechanics-based models were also employed to explain important factors in Young's modulus and yield strength. The theoretical calculation confirmed that the contribution of thermal mismatch, Orowan, elastic mismatch, load bearing and grain boundary strengthening mechanisms to the yield strength are 65.5, 38.3, 26.2, 6.7 and 1.4 MPa, respectively. The Al Si Mg Cu/Mg 2 Si TiB 2 hybrid composite showed a homogeneous distribution of strengthening phases throughout the aluminium matrix, and a microstructure without any detrimental phases. The interfaces between the aluminium matrix and TiB 2 particles were found clean, smooth and well-bonded. And, the TiB 2 particles exhibited hexagonal and cubic prism shapes with chamfered edges and corners. [ABSTRACT FROM AUTHOR]

In this study, an Al-carbon nanotube (CNT) composite with a high hardness of 1.4 GPa and an electrical conductivity of 1.52 × 107 S/m is achieved simultaneously using bare Al nanopowder as a metal matrix. Using bare Al nanopowder, (1) highly dispersed CNTs can be realized because the size of the Al nanopowder is similar to that of the CNTs, and (2) the interface between Al and CNT (Al/CNT interface) can be controlled because of the less oxide layers on the Al particle surface. In particular, fine Al 4 C 3 grains are formed at the Al/CNT interface via annealing at a low temperature of 663 K, which enhances the hardness of the Al-CNT, whereas the remaining Al/Al interface with less oxide layers preserves the electrical conductivity. In conclusion, the Al-CNT composites prepared in this study overcome the trade-off relationship between the hardness and electrical conductivity of the previously reported Al-nanocarbons. The electrical conductivity of the Al-CNT composites in this study is 33 times higher than that of Al-nanocarbons with the same hardness level. [Display omitted] • Al NANO -CNT composites were prepared by using bare Al nanopowder as a matrix. • Al/Al direct bonding interfaces realize high electrical conductivity. • Well-dispersed nucleated Al 4 C 3 nanograin enhanced hardness effectively. • Higher hardness and electrical conductivity were achieved in Al NANO -CNT composite. [ABSTRACT FROM AUTHOR]

The microstructure of a TiPt high temperature shape memory alloy induced by high pressure torsion (HPT) was studied using synchrotron radiation experiments and transmission electron microscopy. Upon the severe plastic deformation, the parent B19 martensite is strongly refined and highly strained. While neither strong chemical disorder nor amorphization are encountered, the occurrence of crystal reflections is observed that can be indexed in terms of the L1 0 phase and long range ordered stacking structures. The occurrence of the L1 0 phase might be triggered by the high hydrostatic stress as well as shear stress superimposed during the HPT. The austenite and martensite start and finish temperatures of TiPt are not affected by the HPT since upon heating, recrystallization occurs prior to the onset of the reverse martensite to austenite transformation. [Display omitted] • High-pressure torsion of TiPt yields a strongly fragmented and strained martensite. • No evidence for amorphization or a reverse B19 to B2 transformation is obtained. • Severe plastic deformation induces a L1 0 phase by high hydrostatic and shear stress. • Recrystallization occurs before the reverse martensite to austenite transformation. [ABSTRACT FROM AUTHOR]

This work studies the influence of gamma prime and eta phases on the pitting corrosion of A286 superalloy by potentiodynamic anodic polarization (PAP) and cyclic potentiodynamic polarization (CPP). The general trend for pitting potential ( E pit ) parameter is that: (i) the higher the aging temperature, the lower the E pit ; and (ii) E pit decreases with increasing aging time. The repassivation potential ( E rp ) allows to study the E pit –E rp difference, which decreases slightly with increasing aging time. The general trend for E pit is altered by the eta phase precipitation at GB which, although it may enhance pit initiation, grows at the expense of gamma prime phase. The general trend for and E pit –E rp is altered by the eta phase precipitation at GB because, even though the nickel-rich eta phase precipitation, just as gamma prime phase precipitation, causes the nickel content of the austenitic matrix to reduce and consequently the repassivation properties to increase, eta phase grows at the expense of gamma prime phase. [ABSTRACT FROM AUTHOR]

The microstructure and crystallographic features of a semi-austenitic precipitation hardening steel PH 15-7Mo during solution treatment, roddrawing and aging were investigated by means of optical microscope, X-ray diffraction analyzer and transmission electron microscope. It was found that the microstructure of the steel was consist of dominant austenite, small amount of martensite and 10–15 vol.% δ-ferrite after solution treatment at 1050 °C followed by cooling in water at room temperature. The austenite transformed into lath martensite during tensile roddrawing about 60% deforming companied with some coherent fine β-NiAl particles precipitated within martensite. With higher aging temperature and longer holding time, tiny carbide M 23 C 6 particles precipitated from martensite, which kept the cubic–cubic orientation relationship (OR) with austenite and G-T OR with martensite which is different with all the reported orientations. The OR between tiny carbide M 23 C 6 particles G-T OR with martensite was discussed in terms of crystallography of phase transformations. [ABSTRACT FROM AUTHOR]

Pure and cerium mixed neodymium orthophosphate was synthesized as nanoparticles via wet chemical co-precipitation technique. Powder X-ray diffraction (PXRD) study suggests that the average crystallite size and X-ray density decreases with the mixing of cerium in neodymium orthophosphate. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies revealed spherical morphology for neodymium orthophosphate but when cerium is mixed the morphology changes into rectangular platelet, like nanorods. Fourier transform infrared (FTIR) spectroscopy signifies slightly shifting of bands towards lower wave number and the force constant were also calculated. Thermal analysis suggests that the material get stabilized after 425 °C and structural phase transition was seen above 800 °C. Optical absorption spectrum give various absorption bands corresponding to each wavelength revealing transitions of Nd 3+ and Ce 3+ present in the UV-VIS region and optical band gap energy decreases from 3.3 to 2.4 eV. Mixing of cerium in neodymium orthophosphate enhances the value of dielectric constant and decreases the transition temperature. The value of exponent ‘n’ suggest that in neodymium orthophosphate, conduction is through hopping mechanism but for cerium neodymium orthophosphate conduction correspond to long range diffusion of ions. [ABSTRACT FROM AUTHOR]

Core-shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites have been synthesized via a facile hydrothermal method employing FeCl 3 ·6H 2 O as the iron source and d -glucose as the carbon source. The core–shell structured γ -Fe 2 O 3 @C nanorods possess a uniform size with ∼500–800 nm in length, the carbon shell's thickness is ∼3–10 nm, and the γ -Fe 2 O 3 core is homogeneously coated by amorphous carbon layer. The measured electromagnetic (EM) parameters show that its maximum reflection loss (RL) can reach −8.11 dB at 3.92 GHz. This is mainly attributed to the multiple-interfacial polarization among the core–shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites. The core–shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites can be a promising candidate for lightweight microwave materials. [ABSTRACT FROM AUTHOR]

Single phase europium doped yttrium aluminum garnet (YAG:Eu) crystallites with good dispersity were successfully synthesized by a facile hydrothermal method at 300 °C for 24 h. The influences of the molar ratio of (Y + Eu) to Al (denoted by Ln/Al) in the raw material on the phase, morphology, crystallinity, local environment of Eu ions and photoluminescence properties were investigated. It was found that the monodispersed single phase YAG:Eu crystallites with terminating faces of {110} can be obtained when Ln/Al is 3:4. Eu ions in all the samples are trivalent regardless of Ln/Al, while the local environment of Eu ions is more symmetric when Ln/Al is 3:4. Moreover, the YAG:Eu crystallites obtained when Ln/Al is 3:4 exhibit improved crystallinity, which contributes to the enhanced luminescence intensity. [ABSTRACT FROM AUTHOR]

Isothermal treatments at 473 K were performed in CuAlNi single crystals to study their effects on the main properties of this shape memory material. Both the stress and thermally induced martensitic transformations were monitored after these ageing treatments. An increase of the critical transformation temperature was detected and the type of induced martensite changed from γ′ into β′ after a long enough ageing time. Pseudoelastic cycling was studied after thermal ageing; mechanical behaviour evolved on cycling and a repetitive behaviour was obtained after a small number of cycles. Changes in microstructure were analysed in the β phase by transmission electron microscopy which allowed observing the morphology and distribution of γ precipitates. The changes obtained in shape memory properties were discussed considering the atomic ordering evolution and characteristics of the precipitates. [ABSTRACT FROM AUTHOR]

The as-quenched Fe–9.0Al–30Mn–1.8C (in wt.%) alloy gas nitrided at 550 °C for 4 h show excellent corrosion resistance investigated in 3.5% NaCl and 10% HCl solutions. Owing to the high corrosion resistance components, the gas-nitrided layer consists mainly of AlN with a slight amount of Fe 3 N and Fe 4 N identified by grazing incidence X-ray diffraction technique. Therefore, the pitting potential and corrosion potential of the nitrided sample are +1860 mV and +30 mV, respectively. Surprisingly, it is worthy to be pointed out that the nitrided and then tensile-tested alloy reveals very shallow in fracture depth and the excellent lattice coherence is shown between the nitrided layer and the substrate. Moreover, due to the extremely high nitrogen concentration (about 17–18 wt.%) at stretched surface, the corrosion resistance of present gas-nitrided and then tensile-tested alloy is superior to those optimally gas-nitrided or plasma-nitrided high-strength alloy steels, as well as martensitic stainless steels. The nitrided and then stretched alloy still retains a satisfactory corrosion resistance ( E pit = +890 mV; E corr = +10 mV). Furthermore, only nanoscale-size pits were observed on the corroded surface after being immersed in 10% HCl for 24 h. [ABSTRACT FROM AUTHOR]

Ternary Co–Al–W alloys with W contents between 8 and 11 at.% were investigated with respect to element partitioning, γ′ solvus, γ′ volume fraction, lattice mismatch and creep properties. W is enriched in the γ′ precipitates and an increasing W content stabilizes this phase. The lattice mismatch is positive up to 900 °C and rafting occurs during creep with a preferred direction in accordance with this positive lattice mismatch. [ABSTRACT FROM AUTHOR]

Direct metal laser sintering (DMLS) is a technique to manufacture complex functional mechanical parts from a computer-aided design (CAD) model. Usually, the mechanical components produced by this procedure show higher residual porosity and poorer mechanical properties than those obtained by conventional manufacturing techniques. In this work, a Co–Cr–Mo alloy produced by DMLS with a composition suitable for biomedical applications was submitted to hardness measurements and structural characterization. The alloy showed a hardness value remarkably higher than those commonly obtained for the same cast or wrought alloys. In order to clarify the origin of this unexpected result, the sample microstructure was investigated by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and energy dispersive microanalysis (EDX). For the first time, a homogeneous microstructure comprised of an intricate network of thin ε (hcp)-lamellae distributed inside a γ (fcc) phase was observed. The ε-lamellae grown on the {111} γ planes limit the dislocation slip inside the γ (fcc) phase, causing the measured hardness increase. The results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields. [ABSTRACT FROM AUTHOR]

This paper represents the first application of small angle neutron scattering (SANS) to the study of precipitate nucleation and growth in β -Ti alloys in an attempt to observe both the precipitation process in-situ and to quantify the evolving microstructure that affects mechanical behaviour. TEM suggests that athermal ω can be induced by cold-rolling Gum metal, a β -Ti alloy. During thermal exposure at 400 ° C , isothermal ω particles precipitate at a greater rate in cold-rolled material than in the recovered, hot deformed state. SANS modelling is consistent with disc shaped nanoparticles, with length and radius under 6 nm after thermal exposures up to 16 h . Modelling suggests that the nanoprecipitate volume fraction and extent of Nb partitioning to the β matrix is greater in the cold-rolled material than the extruded. The results show that nucleation and growth of the nanoprecipitates impart strengthening to the alloy. [ABSTRACT FROM AUTHOR]

The microstructures and properties of W–ZrC composites prepared in situ were compared with those of conventionally prepared W–ZrC and W–(Zr, W)C. In situ preparation led to an ultrafine microstructure with a homogeneous dispersion of ZrC, while the other composites showed microstructures similar to each other. The composite of W containing 30 vol.% (Zr 0.88 W 0.12 )C showed an excellent flexural strength of ∼1425 MPa at 1000 °C. It also showed an excellent flexural strain of 0.051 at 1400 °C, which was obtained by using a maximum displacement of 2.41 mm. Those values have never been reported previously. A similar W composite, in situ W–10 vol.% ZrC, demonstrated a flexural strength of 1324 MPa and a displacement of 0.9 mm under similar conditions. The results of this study are discussed in terms of microstructure and phase stability. [ABSTRACT FROM AUTHOR]

We investigated the microstructure and the crystallography of martensite variants in Ti–Pd–Hf alloy using electron microscopy. The martensitic transformation temperature decreased with increasing amount of Hf substituted into the Ti 50− x Pd 50 Hf x alloy. No indication of a martensitic transformation was observed in the as-quenched Ti 25 Pd 50 Hf 25 and Ti 10 Pd 50 Hf 40 alloys, even when the samples were cooled to 150 K. The Ti 40 Pd 50 Hf 10 , Ti 35 Pd 50 Hf 15 , and Ti 30 Pd 50 Hf 20 alloys were composed of a B19 orthorhombic phase having plate-like habit-plane variants consisting of both major and minor correspondence variants several hundred nanometers in width and several tens of micrometers in length at room temperature. Lattice-invariant shear of these alloys was a {111} B19 Type I twin. A solution-treated sample of the Ti 25 Pd 50 Hf 25 alloy consisted of a B2 cubic matrix with local atomic displacement and lattice distortions, and rounded H-phase particles several tens of nanometers in diameter were precipitated inside the B2 matrix upon aging of the specimen at 823 K for 10.8 ks. The as-quenched Ti 10 Pd 50 Hf 40 alloy contained rounded H-phase particles several tens of nanometers in diameter embedded in a B2 matrix at room temperature. The martensitic transformation temperature in the Ti 50− x Pd 50 Hf x alloy was drastically decreased by both the fully coherent nanosized H-phase particles and the short-range order originating from clustering of solute atoms. [Display omitted] • Transformation temperature decreased with increasing amount of Hf in Ti-Pd-Hf alloy. • B19 martensite in the Ti-Pd-Hf alloy has plate-like habit-plane variants. • As-quenched Ti 10 Pd 50 Hf 40 alloy contained round H-phase particles in a B2 matrix. • Ti 25 Pd 50 Hf 25 alloy consisted of B2 matrix with atomic displacement and distortions. • Nanosized H-phase particles and short-range order inhibit martensitic transformation. [ABSTRACT FROM AUTHOR]

The β-Al 4.5 FeSi phase occurs as plate-shaped particles in secondary, i. e. recycled, Fe-containing hypoeutectic Al-Si alloys and as a component of the intermetallic reaction layer between Al-Si alloys and steels joints. Unsolved issues of the structure interpretation with consequences at all microstructural scales are addressed based on experimental results and new theoretical evidence from DFT calculations. On top of the previously described polytypism (AB and ABCD polytypes, where the letters refer to the positions of a certain type of double layers perpendicular to the stacking direction), ordering of Al vs. Si atoms adds a further aspect of structural variability. Thus, three different ordered crystal structures of β-Al 4.5 FeSi with different ordering of Al vs. Si atoms and different stacking sequences (AB or ABCD) could be encountered in the same alloy. The two AB structures can be described in space groups A 12/ a 1 with (DFT-base) lattice parameters a = 6.1667 Å, b = 6.1683 Å, c = 20.779 Å and β = 91.51° and A 2 1 / e 11 with lattice parameters a = 6.1739 Å, b = 6.1602 Å, c = 20.7840 Å and α = 88.63°. The third structure has ABCD stacking. Unit cell distortions away from a pseudotetragonal orthorhombic metric comply with the symmetry are shown to be induced by the ordering of Al vs. Si atoms. Frequently observed δ-like stacking sequences are discussed as consequence of excess Si in β-Al 4.5 FeSi. Furthermore, recommendation is given for optimal experimental conditions for the characterization of the type of order and polytype in β-Al 4.5 FeSi. [Display omitted] • β-Al 4.5 FeSi has a variable complex hierarchical crystal and defect structure. • Ordering of Al vs. Si adds a further aspect to polytypism. • Crystallographic information for three ordered β structures is provided. • Experimental and theoretical evidence for these structures is given. • Unit cell distortions away from a pseudotetragonal metric comply with the ordering. [ABSTRACT FROM AUTHOR]

The antiphase boundary (APB)-like structure of both 9R and B19 martensites in the Ti–Pd–Fe alloy was investigated by means of transmission electron microscopy. Some APB-like structures with curved and wide contrasts along the (0 0 1) 9R basal plane are observed in 9R martensitic plates. The atomic displacement on the APB-like structure reflects the atomic movement stemming from the microdomains formed as a pre-martensitic transformation. The displacement vector of the APB-like structure in the B19 martensite can be expressed as R = 〈1/3 0 −1/2〉 B19 . The density of APB-like contrasts increases by the substitution of Fe for Pd in Ti–Pd–Fe alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two new metal-rich palladium–indium selenides were synthesized. [•] Their crystal structures were determined from powder XRD and TEM. [•] Electronic structures and bonding were studied using DFT calculations. [•] Multi-centered palladium–indium bonding was revealed using ELF analysis. [Copyright &y& Elsevier]

Highlights: [•] APB-like structures with curved and wide contrasts were observed in martensite of Ti–Ni–Fe alloy. [•] APB-like structure via R-phase exhibited facets composed of the (010), (001), and (100) planes. [•] APB-like structure reflects the atomic movement stemming from the R-phase transformation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cubic Ti0.9W0.1C is formed after 50min of milling of α-Ti, W and graphite powders. [•] Nanocrystalline Ti0.9W0.1C with particle size ∼11nm is obtained after 8h milling. [•] Average particle size of Ti0.9W0.1C from XRD analysis and HRTEM is very close. [•] Formation of Ti0.9W0.1C is hindered as compared with TiC. [ABSTRACT FROM AUTHOR]

Highlights: [•] Solid-state amorphization (SSA) of Ti-rich intermetallic compounds (Ti>50at.%) was investigated. [•] SSA of C11b–Ti2Pd under MeV electron irradiation was observed by high-voltage electron microscopy. [•] Decomposition of C11b–Ti2Pd to bct solid solution occurred prior to SSA. [Copyright &y& Elsevier]

Abstract: Nanoparticles of Co1−x Zn x Fe2−x Cr x O4 (x =0.0–0.5) ferrites were prepared by chemical co-precipitation technique using metal sulphates. The structural and magnetic properties were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and AC susceptibility measurements. X-ray diffraction patterns indicate that the samples possess single phase cubic spinel structure. The lattice constant initially increases for x ≤0.3 and thereafter for x >0.3 it decreases with increasing x. The saturation magnetization (Ms), magneton number (n B) and coercivity (Hc) decreases with increasing Cr–Zn content x. Curie temperature deduced from AC susceptibility data decreases with increasing x. [Copyright &y& Elsevier]

Abstract: Martensitic transformation of as-rolled and 1323K×1h annealed Ni64Al34.5Re1.5 (NiAl–1.5Re) shape memory alloy (SMA) is investigated. For as-rolled NiAl–1.5Re alloy, TEM and EPMA results indicate both 14M and 3R martensites are observed at the room temperature. 14M is formed in the precipitate-free zone which is a Ni-depletion region and 3R is formed in the matrix which is a Ni-enrichment region. XRD and partial-cycle DSC testing results show that the higher temperature peak of the DSC cooling curve is B2→14M and the lower one is B2→3R. Hardness tests show that 14M hardness is higher than that of 3R. For annealed NiAl–1.5Re alloy, only B2↔3R can be observed. The critical value for the formation of 14M martensite in NiAl–1.5Re alloy is about 63.6at.% Ni, as compared to 63.0at.% Ni for Ni–Al binary SMAs. [ABSTRACT FROM AUTHOR]

• The self-consistency of thermal and structural data on Ga - S system was fulfilled. • The renewed T-x-diagram of the Ga–S system is obtained. • 4 polymorphic modifications were found in the narrow range close to Ga 2 S 3 composition. • The 2D-defect {111} planes in γ-Ga 2+δ S 3 phase were observed with atomic resolution. • The relations between the family of polymorphic Ga 2 S 3 -structures were examined. [Display omitted] This article opens a series of publications devoted to the preparation and stabilization of new high-temperature (HT) semiconductor phases A (III) – B (VI), which have a large number of vacancies and possess a number of unique properties. In this first work from the proposed series, the T - x -diagram of the Ga–S system was investigated in the composition range x = (30.0–60.7) mol% S, and then the structural identification of new HT phases was carried out. For the Ga–S system, four polymorphic (α-, α′-, β-, γ-) Ga 2 S 3 phases of different symmetry were found and displayed on the phase diagram near the Ga 2 S 3 composition (x ∼ 60.0 mol% S). For the first time, it became possible to obtain in-situ a reliable direct proof for the existence of equilibrium in narrow temperature range for the re-opened cubic phase γ-Ga 2+δ S 3 (x ≈ 59.0 mol% S), which was isolated at room temperature in a fairly pure form. We also confirmed the presence of another hexagonal β(α)-Ga 2 S 3 modification, existing at much higher temperatures than the cubic γ-Ga 2+δ S 3 phase. It was shown that the polymorphic α-Ga 2 S 3 and α′-Ga 2 S 3 phases mentioned in the literature form superstructures from the parent β-Ga 2 S 3 phase. The observed structural variants for all four Ga 2 S 3 polymorphic phases, containing up to 1/ 3 of vacancies in the Ga sub-lattices, are closely related to different methods of ordering Ga vacancies. The reliability of our studies follows from the combination of the methods used: differential thermal analysis (DTA), microstructural local analysis (TEM, HREM, SAED), powder X-ray diffractometry (XRD), including high-temperature synchrotron XRD. [ABSTRACT FROM AUTHOR]

Abstract: A Ag–4wt.% Er solid solution alloy was produced by arc melting and quenching to room temperature. When this alloy was annealed in air at various temperatures, the Er was converted to ∼1-μm thick Er2O3 lamellae in the Ag matrix. Subsequent swaging and stress-relief annealing converted the lamellar microstructure to predominantly spheroidal Er2O3 particles. The alloys were examined by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electrical resistivities of 2.0–3.3μΩcm and hardness values of 83–162HV were measured. [Copyright &y& Elsevier]

Abstract: Hematite nanoparticles in a silica matrix containing 30wt.% of hematite were synthesized by the sol–gel method. Transmission electron microscopy studies showed that the average particle size of the hematite was about 4nm with a narrow size distribution, while selected area electron diffraction confirmed the formation of the hematite phase. Investigation of the magnetic properties by DC magnetization and AC susceptibility measurements indicated behavior typical of a superparamagnetic system, such as the existence and frequency dependence of a blocking temperature, irreversibility of the zero-field-cooled (ZFC) and field-cooled (FC) curves, and emergence of magnetic hysteresis below the blocking temperature. Quantitative analysis of the DC magnetic data indicated that the system consisted of an assembly of superparamagnetic nanoparticles with a narrow size distribution, while the AC data implied the existence of weak inter-particle interactions. [Copyright &y& Elsevier]

• Glassy FeNiBPSiC alloy ribbons with attractive soft magnetic properties were obtained in melt-spun state. • The partial replacement of Fe by Ni leads to the change from BCC to FCC solid solution in co-precipitated phases. • Ni addition increase the thermal stability of glassy phase and move the isothermal crystallization to SCL region. • The glassy 0.5Ni and 0.6Ni alloys possess the large SCL region, higher GFA and good magnetic softness in the as-spun state A glassy phase is formed over the whole composition range for melt-spun (Fe 1−x Ni x) 79 B 12 P 5 Si 3 C 1 with x = 0; 0.2; 0.4; 0.5; 0.6 alloy ribbons and these glassy ribbons exhibit good bending plasticity. The Ni-containing glassy alloys show glass transition, followed by a supercooled liquid (SCL) region and then multistage crystallization for the alloys with x = 0.5 and 0.6 (hereafter 0.5Ni and 0.6Ni alloys). The 0.5Ni glassy alloy exhibits the largest SCL region of 43 K and good soft magnetic properties even in as-spun state, i.e., low coercive force of 4.8 A/m, effective permeability of 7400 at 1 kHz and saturation magnetization of 0.80 T. The bending plasticity remains unchanged in the wide annealing temperature range below T g. The crystallization proceeds in the processes of glassy (G) → bcc(α)Fe(Si) + Fe 3 B for the 0–0.2 Ni alloys, G → fcc(γ)(Fe,Ni) + Fe 3 (B,C) + Fe 3 Ni 3 (B,C) for the 0.4Ni alloy and G → G' + γ(Fe,Ni) → γ(Fe,Ni) + Ni 5 P 2 + Fe 4 P + Fe 3 Ni 3 (B,C) for the 0.5Ni and 0.6Ni alloys. Analyses of crystallization reaction in isochronal and isothermal conditions were performed via Kissinger and JMAK models and the activation energy for crystallization is much larger for the 0.5Ni glassy alloy. The appearance of the largest SCL region as well as the highest activation energy for the 0.5Ni alloy is due to the necessity of the simultaneous decomposition to the four crystalline phases. The better magnetic softness for the 0.5Ni alloy is presumably due to the development of medium-range ordered atomic configurations which enable the appearances of the largest SCL region as well as the lower internal stress state. The combination of useful properties for the 0.5Ni glassy alloy is promising for useful soft magnetic materials with mass production ability. [ABSTRACT FROM AUTHOR]

The atomic structure of Ω plates forming on {111} Al planes in an Al-Cu-Mg-Ag alloy has been investigated by Z -contrast atomic-resolution scanning transmission electron microscopy imaging and ab initio density functional theory calculations. Ω plates with different thicknesses have been studied in two peak-aged conditions: 150 °C for 24 h and 190 °C for 1.5 h. Volumetric and structural incompatibilities as unrelaxed misfit strains and shear components, respectively, between the Ω plates involving orthorhombic θ-phase fragments and Al matrix were found to be in the plates with thicknesses from 0 to 2.5 c θ (a normal direction to {111} Al). Two types of shear components: [−101] Al // [0−10] θ (τ I) and [1−21] Al // [100] θ (τ II) related to precipitate/matrix structural incompatibilities have been predicted by calculations. The shear components τ I and τ II have been found to be energetically favorable in the plates with different thicknesses. Comparing τ I and τ II absolute values in supercells involving the plates with different thicknesses, 2 c θ thick plates have a shear component close to zero. All the plates analyzed have precipitate/matrix volumetric incompatibilities with Al matrix as misfit strains along [111] Al // [001] θ , which distribute non-uniformly across the plate thickness. Large misfit strains concentrate at the broad plate interfaces, i.e. in Ag 2 Cu and Cu i layers, and cause a prohibitively high barrier to thickening of the Ω precipitates. • {111} Al Ω plates have been analyzed in an peak-aged Al-Cu-Mg-Ag alloy • Plates with different thicknesses have incompabilities with the Al matrix • Density functional theory was applied to parameterize these incompatibilities • These incompatibilities qualitatively change during the plate thickening [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) of tool steels offers a great potential for tailoring material properties besides technical advantages like great freedom of design or function integration. In this study, a novel high-strength Fe85Cr4Mo8V2C1 tool steel processed by LPBF and by casting was examined in a comparative study. By means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) for both conditions a microstructure composed of martensite, austenite and complex carbides was detected. Very high cooling rates of LPBF yield a significant microstructural refinement across the building direction with much more homogenous distribution of the principal phases compared with the cast counterparts. The corrosion behavior was investigated in NaCl solutions by means of potentiodynamic polarization measurements as well as surface analysis with SEM and X-ray photo electron spectroscopy (XPS) after immersion testing. Particulary in more aggressive solutions where active dissolution dominates, i.e. in 3.5% NaCl (pH 7) and in 0.035% NaCl (pH 3), the LPBF samples exhibit a retarded corrosion activity according to more positive corrosion potentials and significantly lower corrosion current densities as well as reduced anodic current densities. A wave-like corrosion pattern was detected reflecting melt track-related microstructural features, i.e. local grain coarsening and preferred crystal orientation. In milder solution, 0.035% NaCl (pH 7), Fe85Cr4Mo8V2C1 exhibits for both processing conditions relatively low free corrosion rates. For LPBF samples a complex, fine grain boundary network supports the formation of thicker but slightly more permeable layers composed mainly of iron oxides which retard the corrosion activity especially at higher anodic polarization. [Display omitted] • Fe85Cr4Mo8V2C1 processed by laser powder bed fusion (LPBF) and casting. • Microstructure of both conditions consists of martensite, austenite, MC- and M 2 C. • Refined microstructure and more homogenous element distribution by LPBF. • Increased corrosion resistance for LPBF state compared to cast counterpart. • Retarded corrosion activity in more aggressive NaCl solutions for LPBF condition. [ABSTRACT FROM AUTHOR]

• The Zr-2.5% Nb alloy was processed by HPT in the temperature range from RT to 325 °С. • HPT leads to the grain refinement and to the α-Zr → ω-Zr phase transformation. • The microstructure of the Zr-alloy after HPT is characterized by significant inhomogeneity. • With an increase in the HPT temperature from RT to 325 °C, the amount of the ω-phase decreases. • With an increase in the HPT temperature from RT to 325 °C, the thermal stability of the ω-phase increases. The effect of the temperature of the high-pressure torsion (HPT) deformation and subsequent annealing in a wide temperature range on the structural and phase transformations in the Zr-2.5% Nb alloy and its microhardness has been studied. In the course of the HPT process, the grain structure in the alloy is refined to the nano- and submicron level, the density of crystal defects increases and the α-Zr → ω-Zr phase transformation occurs, which are accompanied by an increase in the microhardness values. The microstructure of the alloy after HPT is characterized by significant inhomogeneity, and the crystallite size increases slightly with increasing the HPT temperature. Annealing of the HPT-processed alloy samples leads to their softening due to the reverse ω-Zr → α-Zr phase transformation and due to the grain growth. With an increase in the HPT-deformation temperature from room temperature to 325 °C, the amount of the ω-Zr phase in the alloy structure decreases, while its thermal stability increases. The HPT-processed Zr-2.5% Nb alloy has an advantage for medical applications compared to other commercial zirconium alloys. [ABSTRACT FROM AUTHOR]

We studied the crystallographic characteristics of the Al 18 Mg 3 Ti 2 intermetallic phase in a solution-treated Al–7.6Zn–2.6Mg–2.0Cu–0.1Zr–0.07Ti (wt.%) alloy utilizing transmission electron microscopy (TEM). Cubic spinel Al 18 Mg 3 Ti 2 intermetallic phase features { 111 } faceted interfaces with the Al matrix. Selected-area electron diffraction pattern, stereographic projection, and atomic projection studies indicated four possible orientation relationships between the Al 18 Mg 3 Ti 2 phase and the Al matrix, which are categorized by a misorientation angle (θ) at { 111 } planes of each phase (i.e., θ = ± m , 70.5°± m , where m = 12–14°). High resolution TEM analyses confirmed that the growth of the Al 18 Mg 3 Ti 2 intermetallic phase is based on the ledge mechanism on the { 111 } interfaces along with multiple { 111 } twinning. This growth mechanism of the Al 18 Mg 3 Ti 2 phase contributes to the formation of faceted morphologies with { 111 } interfaces. The interface between the Al 18 Mg 3 Ti 2 phase and Al matrix provides a heterogeneous nucleation site for the L1 2 -precipitate and a Zn-rich phase. • Al 18 Mg 3 Ti 2 intermetallic phases with {111} facets are observed. • Four orientation relationships (ORs) between Al 18 Mg 3 Ti 2 and Al are classified. • Al 18 Mg 3 Ti 2 phase grows by ledge mechanism on {111} planes and multiple twinning. • Al 18 Mg 3 Ti 2 interfaces are heterogeneous nucleation sites of L1 2 - and Zn-phases. [ABSTRACT FROM AUTHOR]

Paper deals with the Al/NiO high temperature interaction leading to creation of complex microstructure. Its comprehensive characteristics with means of scanning and transmission electron microscopy have been described. Application of various orientations of NiO substrate resulted in the formation of the same phase composition (α-Al 2 O 3 , Al and Al 3 Ni), however of various morphology and amount of particular components, depending on NiO crystallographic orientation. Regardless, of applied substrate orientation, alumina particles of submicron size were formed, which surrounded by aluminum matrix can be treated as model Al–Al 2 O 3 composite formed in situ . The formation of Al 3 Ni phase was discussed with help of calculated stable and metastable Al–Ni–O phase diagrams. [ABSTRACT FROM AUTHOR]

Abstract: The crystallite and grain sizes of pure copper milled at cryogenic temperature for different periods have been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). X-ray line profile analysis using a modified Williamson–Hall method [T. Ungár, Á. Révész, A. Borbély, J. Appl. Crystallogr. 31 (1998) 554], which takes into account the strain anisotropy induced by dislocations and planar faults, was used to determine the size of the coherently scattering domains. The results reveal that the modified Williamson–Hall method leads to values that are in very good agreement with the data obtained by TEM, in particular when considering the effect of planar faults. [Copyright &y& Elsevier]