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Martensitic transformation, magnetic entropy, and direct adiabatic temperature changes in Ni48Mn39.5Sn12.5−xInx (x = 2, 4, 6) metamagnetic Heusler bulk and grain-constrained ribbon alloys were studied. All alloys showed a typical L21 structure in austenite and the 4O structure in martensite. Their relative volume contributions changed depending on In content. With increasing In concentration, the martensitic transformation temperature increased, whereas the Curie temperature of austenite decreased. The magnetic entropy change under magnetic field of 5 T attained maximum of 20 J/kgK in the bulk and 14.4 J/kgK in the ribbon alloys with the Ni48Mn39.5Sn8.5In4 nominal composition. The corresponding adiabatic temperature change under 1.7 T yielded 1.3 K for the Ni48Mn39.5Sn8.5In4 bulk alloy. Despite grain confinement, melt spinning was found to stabilize martensite phase. Changes observed were discussed with relation to strengthened covalency imposed by In substitution. Graphic abstract

This work concerns microstructure and mechanical properties investigations of aluminum based composite strengthened with the TiC particles being in nanometer size. The composites were fabricated by the casting method combined with in-situ formation of TiC particles. Applying a suitable composition of components and moderators of SHS reaction which occur during casting, it was possible to cast the samples with TiC particles of size of 150 nm and faceted shape. Microstructure investigations using scanning and transmission electron microscopy (SEM and TEM) allowed to identified the distribution of TiC particles and their preferred location in the microstructure of composites. Also the additional precipitates with different size and shape were identified in investigated samples. Significant increase of strength was observed in in-situ cast composites in comparison to Al-1000 alloy mainly due mainly due to coefficient of thermal expansion and elastic modulus mismatch between the reinforcements and the metal matrix, Hall-Pecht relation and also in minority the Orowan effect.

We present a study of the annealing effect and its influence on magnetic and structural properties for a series of Heusler alloys Ni50−xCoxMn35.5In14.5 (x=0,3,5) prepared in ribbon form. We studied the morphology and composition using scanning electron microscopy (SEM) equipped with an X-ray microanalyzer (EDX). The magnetic properties were determined by two methods: electron magnetic resonance (EMR) and vibrating sample magetometer (VSM). We found that cobalt content in the annealed samples reveals an additional magnetic phase transition at lower temperatures.

We report observation of non-conventional twins (i.e. twins with neither the twinning plane being a lattice plane, nor the twinning direction being a lattice vector) in five-layer modulated martensite of the Ni-Mn-Ga ferromagnetic shape memory alloy. The twins were observed using scanning and transmission electron microscopy, and identified by calculations using the mathematical theory of martensitic microstructures.

The effect of cobalt addition instead of nickel on the crystal structure, martensitic transformation behaviour and shape memory effect were investigated. Within the analysed range of chemical compo...

The complex structural and magnetic studies of the annealed rapidly quenched Cu-free Fe72Ni8Nb4Si2B14 alloy (metallic ribbons form) are reported here. Based on the calorimetric results, the conventional heat treatment process (with heating rate 10 &deg, C/min and subsequent isothermal annealing for 20 min) for wound toroidal cores has been optimized to obtain the least lossy magnetic properties (for the minimum value of coercivity and magnetic core losses at 50 Hz). For optimal conditions, the complex permeability in the 104&ndash, 108 Hz frequency range together with core power losses obtained from magnetic induction dependence up to the frequency of 400 kHz was successfully measured. The average and local crystal structure was investigated by the use of the X-ray diffraction method and the transmission electron microscopy observations and proved its fully glassy state. Additionally, for the three temperature values, i.e., 310, 340 and 370 &deg, C, the glass relaxation process study in the function of annealing time was carried out to obtain a deeper insight into the soft magnetic properties: magnetic permeability and cut-off frequency. For this type of Cu-free soft magnetic materials, the control of glass relaxation process (time and temperature) is extremely important to obtain proper magnetic properties.

Fe50Ni28Co17Al11.5Ta2.5 single crystals oriented along the [001] direction were investigated in order to establish the influence of two-step aging conditions on superelastic properties. The homogenized and quenched single crystalline material was subjected to a combination of high-temperature and low-temperature heat treatment at 973 K for 0.5 h and at 723 K for various aging times, respectively. As a result, fine and coherent &gamma, &rsquo, precipitates were formed. Using diffraction of high energy synchrotron radiation, the volume fraction of &gamma, precipitates was computed while their size was determined by high resolution TEM analysis. Compared with one-step heat treatment, the two-step aging process enables control of the precipitate size in a more accurate way. Moreover, it allows one to obtain a higher volume fraction of precipitates without increasing their size significantly. The obtained coherent &gamma, precipitates ranged in size from 5 to 8 nm, that considerably improved mechanical properties. The highest superelastic response was obtained for single crystals aged at 973 K for 0.5 h followed by aging at 723 K for 3 h. The single crystals treated with such conditions exhibited a superelastic strain of 15% in which the mechanical martensite stabilization was substantially suppressed.

Ordering effects in the Ni49Co1Mn37.5Sn6.5In6 alloy were studied by subjecting the alloy to annealing at 1220 K followed by water quenching and to subsequent annealing at 1070 K followed by slow cooling. Martensitic transformation temperature increases by 10 K owing to the slow cooling process, which further invites a change in the martensite structure: 6M → 10M. Across the transformation, regardless of the heat treatment applied, austenite phase is paramagnetic and it transforms into a weakly magnetic martensite. Magnetic moment of martensite is boosted due to slow cooling ( $$ \Delta \mu_{\text{eff}}^{\text{M}} = 1 \mu_{\text{B}} $$ ). Observed behaviours are associated with the changes in the degree of atomic ordering. Irrespective of the magnetic state of martensite, ordering process mitigates the transformation temperature most likely through the interaction with the free energy difference and through the influence of antiphase domains on the twinning stress.

The technology of structure refinement in materials with the aim of achieving substantial mechanical properties and maintaining the required plasticity level is becoming increasingly useful in industrial practice. Magnesium alloys are very progressive materials for utilization in practice thanks to their high strength-to-weight ratios (tensile strength/density). The presented paper analyses the effect of the input heat treatment of the AZ31 alloy on the change of structure and strength properties through the process of severe plastic deformation (SPD), which finds an increasing utilization, especially in the automotive and aviation industry. For the study of the influence of the SPD process (ECAP method) on the properties of the AZ31 alloy, two types of thermal treatment of the initial state of the structure were selected. The analysis of the structure of the AZ31 alloy was performed in the initial state without heat treatment and subsequently after heat treatment. In the next part, the influence of the number of passes on the strengthening curves was evaluated. Mechanical properties of the AZ31 alloy after ECAP were evaluated by hardness measurement and completed by structure analysis.

In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe84.5-xCoxNb5B8.5P2 (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on a semi-industrial scale by the melt-spinning technique. The subsequent nanocrystallization processes were carried out under different conditions (with/without magnetic field). The comprehensive studies have been carried out using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hysteresis loop analyses, vibrating sample magnetometry and Mössbauer spectroscopy. Moreover, the frequency (up to 300 kHz) dependence of power losses and permeability at a magnetic induction up to 0.9 T was investigated. On the basis of some of the results obtained, we calculated the values of the activation energies and the induced magnetic anisotropies. The X-ray diffraction results confirm the surface crystallization effect previously observed for phosphorous-containing alloys. The in situ microscopic observations of crystallization describe this process in detail in accordance with the calorimetry results. Furthermore, the effect of Co content on the phase composition and the influence of annealing in an external magnetic field on magnetic properties, including the orientation of the magnetic spins, have been studied using various magnetic techniques. Finally, nanocrystalline Fe64.5Co20Nb5B8.5P2 cores were prepared after transverse thermo-magnetic heat treatment and installed in industrially available portable heating equipment.

Electron microscopy techniques were used to characterize the microstructure and deformation behavior of AZ61 alloy proceeded by ECAP. The commercial AZ61 alloy subjected to severe plastic deformation possesses a two-phase microstructure consisting of solid solution matrix and massive γ-phase Mg17Al12, or Mg17(Al,Zn)12 distributed mostly at grain boundaries. Based on selected area diffraction and electron back scattered diffraction applied to a sample after the third pass, it can be concluded that plastic deformation induced by ECAP occurs mainly by slip mode forming a high density network of dislocation inside the grains. The grains size was significantly refined to 1.4 μm after the third pass of ECAP. The refinement of grain size is probably due to polygonization process associated with formation of high angle grain boundaries due to dislocations rearrangement. (Al, Zn)12Mg17 precipitates of size scattered from 100 to 200 nm and also the primary precipitates of Al6Mn phase were observed in this alloy.

Ga&ndash, Sn&ndash, Zn eutectic alloy is a non-toxic liquid metal alloy which could be used in a multitude of applications, including as a heat transfer agent, in gas sensing, and in medicine. Alloys containing gallium readily oxidise in air, forming a thin oxide layer that influences the properties of liquid metals and which has not been studied. In this study, the oxide layer formed on Ga&ndash, Zn alloy was transferred at room temperature onto three substrates&mdash, quartz, glass and silicon. The contact angle between the liquid alloy and different substrates was determined. The obtained thin oxide films were characterised using atomic force microscopy, X-ray photon spectroscopy, and optical and transmission electron microscopy. The contact angle does not influence the deposition of the layers. It was determined that it is possible to obtain nanometric oxide layers of a few micrometres in size. The chemical composition was determined by XPS and EDS independently, and showed that the oxide layer contains about 90 atom % of gallium with some additions of tin and zinc. The oxides obtained from the eutectic Ga&ndash, Zn liquid alloys appear to be nanocrystalline.

Selective Laser Melting was successfully used as a fabrication method to produce Ni-Mn-Ga and Ni-Mn-Ga-Fe ferromagnetic shape memory alloys. The starting material in a powder form with an average particle size of about 17.6 µm was produced by milling of as melt-spun ribbons. The microstructure, phase composition, and martensitic transformation behavior of both powder precursors and laser melted alloys were investigated by several methods, including high energy X-ray diffraction, electron microscopy, and vibrating sample magnetometry. The as laser melted materials are chemically homogenous and show a typical layered microstructure. Both alloy compositions have a duplex structure consisting either of austenite and 10M martensite (Ni-Mn-Ga) or a mixture of 14M and NM martensitic phases (Ni-Mn-Ga-Fe), contrary to the as milled powder precursors showing fcc structure in both cases. The forward martensitic transformation takes place at 336 and 325 K for Ni-Mn-Ga and Ni-Mn-Ga-Fe, respectively, while the magnetic response is much stronger for Ni-Mn-Ga than for the quaternary alloy. The results show that Selective Laser Melting allows for producing of good quality, homogenous materials. However, their microstructural features and consequently shape memory behavior should be tailored by additional heat treatment.

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe72−xNi8Nb4CuxSi2B14 alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔGamorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔGmix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures Tx1onset and Tx1 of the alpha-iron phase together with the activation energy Ea for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 104 Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).

Materials and design 197, 109225 (2021). doi:10.1016/j.matdes.2020.109225, The study focuses on the superelastic effect in single-crystalline boron-doped Fe-based shape memory alloys. Thehomogenized and quenched single crystals were subjected to a heat treatment at 973 K for variable aging times.As a result, small and coherent nanometer-sized $γ′$ (Ni$_3$Al-type) precipitateswere formed. Itwas established thatFe-28Ni-17Co-11.5Al-2.5Ta-0.05B single crystals oriented along [001] direction exhibit the fully reversiblesuperelastic behavior up to 14.3% compression strain at 77 K reaching the maximum theoretical value. Theboron addition suppressed completely the formation of the brittle $β$ phase and reduced the average precipitatesize of the $γ′$ precipitates. Using high-energy synchrotron radiation and high-resolution transmission electronmicroscopy analysis the volume fraction and precipitate size of $γ′$ were determined indicating that both factorsare critical in obtaining the largest superelastic reversibility. Boron addition counters the initial effect of mechanicalstabilization which was detected in single crystals without boron. Unlike the thermally induced martensitictransformation, applied stresses produce a different austenite/martensite interface composed of interchangingaustenite and martensite variants. It is also demonstrated that upon loading/unloading cycles the moving transformationfront divides the material into three district regions i.e. single variant of austenite, austenite intermixedwith martensite and single variant of martensite., Published by Elsevier Science, Amsterdam [u.a.]

2D TiO2 thin films and 3D flower-like TiO2-based nanostructures, also decorated with SnO2, were prepared by chemical and thermal oxidation of Ti substrates, respectively. The crystal structure, morphology and gas sensing properties of the TiO2-based sensing materials were investigated. 2D TiO2 thin films crystallized mainly in the form of rutile, while the flower-like 3D nanostructures as anatase. The sensor based on the 2D TiO2 showed the best performance for H2 detection, while the flower-like 3D nanostructures exhibited enhanced selectivity to CO(CH3)2 after sensitization by SnO2 nanoparticles. The sensor response time was of the order of several seconds. Their fast response, high sensitivity to selected gas species, improved selectivity and stability suggest that the SnO2-decorated flower-like 3D nanostructures are a promising material for application as an acetone sensor.

Microstructure, martensitic transformation behavior and magnetic properties of Ni 44− x Fe x Co 6 Mn 39 Sn 11 ( x = 0, 1, 2 at.%) melt spun ribbons have been investigated. The influence of iron addition has been thoroughly studied by means of electron microscopy, X-ray diffraction and vibrating sample magnetometry. The results show that addition of 1 at.% of iron into quaternary Ni–Co–Mn–Sn Heusler alloy drastically decreases the martensitic transformation temperature by more than 100 K. Higher concentration of iron leads to complete suppression of martensitic transition. The structure of samples change from fully martensite (12 M) through mixed austenite-martensite (L2 1 + 10 M) to fully austenite (L2 1 ) with increase of iron content. Addition of 1 at.% of iron leads to enhance magnetization of both austenitic and martensitic phases and also a small increase of Curie temperature occurs. The largest change of magnetic entropy under 15 kOe measured 2.9 and 0.65 J kg −1 K −1 for alloys where x = 0 and 1, respectively.

The main goal of this work was to examine the effect of aging process on the precipitation behavior including phase morphology, chemical composition and degree of coherence in Fe–28Ni–17Co-11.5Al-2.5Ta single crystals. The nano-sized and coherent γ′ precipitates were used for strengthening process. The particles were investigated with transmission and scanning electron microscopies along with high energy X-ray diffraction. The single crystalline material of [100] (001) orientation was subjected to three different heat treatments: slowly cooled, quenched and then annealed with various aging conditions. Aging at 973 K for short times results in coherent 2-6 nm-sized γ′ precipitates and fully reversible superelastic strains while annealing at 973 K for 5 h and longer times leads to the precipitation of larger γ’ particles formed together with β phase which significantly reduces the transformed martensite volume fraction.

In this work, a detailed microstructural investigation of as-melt-spun and heat-treated Fe67Co20B13 ribbons was performed. The as-melt-spun ribbon was predominantly amorphous at room temperature. Subsequent heating demonstrated an amorphous to crystalline &alpha, (Fe,Co) phase transition at 403 &deg, C. In situ transmission electron microscopy observations, carried out at the temperature range of 25&ndash, 500 &deg, C and with the heating rate of 200 &deg, C/min, showed that the first crystallized nuclei appeared at a temperature close to 370 &deg, C. With a further increase of temperature, the volume of &alpha, (Fe,Co) crystallites considerably increased. Moreover, the results showed that a heating rate of 200 &deg, C/min provides for a fine and homogenous microstructure with the &alpha, (Fe,Co) crystallites size three times smaller than when the ribbon is heated at 20 &deg, C/min. The next step of this research concerned the influence of both the annealing time and temperature on the microstructure and coercivity of the ribbons. It was shown that annealing at 485 &deg, C for a shorter time (2 s) led to materials with homogenous distribution of &alpha, (Fe,Co) crystallites with a mean size of 30 nm dispersed in the residual amorphous matrix. This was reflected in the coercivity (20.5 A/m), which significantly depended on the volume fraction of crystallites, their size, and distribution.

In this work, results of structural studies, performed as a function of temperature (13–1073 K) of Na0.72CoO2 cathode material, are presented, together with microstructural measurements, including detailed transmission microscopy examination, as well as electrochemical studies, showing current rate-dependent charge/discharge characteristics and also voltammetry tests. It was found that thermal expansion of P2 type (P63/mmc) Na0.72CoO2 differs along a- and c-axes. Microstructural studies showed platelet-like grains of the synthesized sodium cobaltate, while detailed transmission microscopy measurements indicated coexistence of well-defined layered regions with regions having somewhat disturbed atomic arrangement. For higher current densities, characteristic plateaus observed on Na/Na+/NaxCoO2 charge/discharge curves diminish, and the voltage dependence on the sodium concentration is smoothed out. Results of the electrochemical tests, performed on cathodes without any carbon additives, indicated that in fact, such additives influence electrochemical behavior during first charge considerably. Additional voltammetry investigations confirmed presence of nine characteristic anodic and cathodic peaks, corresponding well with plateaus observed during charge/discharge of the cells.

Copper matrix composites strengthened with graphene were prepared by vacuum uniaxial hot pressing of ball milled mixtures of powders. Two grades of graphene platelets were used; one with thickness of 10–20 nm and with lateral size of less than 14 μm and another with much lower thickness of platelets of 2–4 nm and in (002) plane crystallite size below 100 nm. Hot pressing in vacuum allowed obtaining composites containing 1 and 2 wt% of graphene. The addition of fine graphene led to about 50% higher hardness and about 30% lower electrical resistivity than composite with coarse graphene platelets. SEM studies of samples with fine graphene additions showed much more homogeneous microstructure than those containing coarse graphene. Based on TEM studies, copper particle size was estimated between 100 and 300 nm, and smaller in the areas of copper particle boundaries, where plastic deformation of copper particles brought about mixing nanocrystalline copper and graphene phases. Graphene conglomerates were identified using electron diffraction and often consisted of elongated platelets of thickness up to 20 nm in both graphene composites studied. Raman spectra confirmed nonhomogeneity of graphene in bulk composites and showed increase of defect density within graphene platelets, as was assessed from low intensity ratio I (2D)/ I (G), in places of high graphene concentration in both kinds of samples. The weak signal in more homogeneously distributed graphene in samples with fine graphene additions confirmed similar structural features, however the lateral size of finer graphene remain unchanged in composites, contrary to that with coarser graphene additions.

The data collected from electronic nose systems are multidimensional and usually contain a lot of redundant information. In order to extract only the relevant data, different computational techniques are developed. The article presents and compares selected pattern recognition algorithms in application to qualitative determination of different brands of tea. The measured responses of an array of 18 semi- conductor gas sensors formed input vectors used for further analysis. The initial data processing consisted on standardization, principal component analysis, data normalization and reduction. Soft computing one can divide into single method systems using neural networks, fuzzy systems, and hybrid systems like evolutionary-neural, neuro-fuzzy, evolutionary-fuzzy. All the presented systems were evaluated based on accuracy (generated error) and complexity (number of parameters and training time) criteria. A novel method of forming input data vector by aggregation of the first three principal components is also presented.

An electrospinning technology have been developed to obtain zinc oxide nanofibres doped with aluminum. Properties of the obtained nanostructures can be controlled by both the composition of a precursor and subsequent annealing treatment. The gas sensors manufactured with the use of ZnO:Al nanofibres exhibit good response to NO2 at relatively low operating temperatures. For some samples it was observed that interaction with ambient NO2 gas causes the change of conductivity from n-type to p-type at higher operating temperatures. This phenomenon was not observed for the samples annealed at higher temperature.

Four alloys with nominal compositions Ni46Mn41.5-xFexSn12.5 (x=0, 2, 4, 6 at.%) were cast in an induction vacuum furnace and homogenized. Then they were melted in quartz tubes and ejected onto a rotating copper wheel to produce ribbons. The X-Ray phase analyses of as melt spun ribbons have shown that in both, the ternary as well as in the quaternary alloys a single phase of the Heusler L21 type ordered structure was found. The characteristic temperatures of magnetic (TC) and martensitic (Ms) transformations were determined by a vibrating sample magnetometer (VSM). Both the Ms and TC increase with the increase of Fe content in all alloys, which is in accordance with the theory of valence electron concentration (e/a) influence on Ms. The phase structures, chemical compositions, grains sizes and type of microsegregation were characterized by transmission electron microscope (TEM). The equi-axed grains of size from 0.95 to 1.7 μm were observed in all ribbons. The grains posses the L21 structure at room temperature, however in the alloys with higher Fe content the different type of martensite was observed at the grain boundaries of L21 phase. Appearance of this martensite was explained in relation to microsegregation of particular elements during melt spinning process and simultaneous change in the e/a ratio.

A prospective high temperature polycrystalline Ni50Mn44Sn6 Heusler shape memory alloy transforms at 637 K into 14 M and NM martensites with a14M = 6.278, b14M = 6.127, c14M = 5.654; and aNM = 5.449, cNM = 6.380 A lattice parameters, theoretically yielding 9.9% (14 M) and 14.6% (NM) mechanically induced strain due to detwinning of martensite in single crystal. The substitution of Ni for Co, Cu and Fe (5 at.%) brings the martensitic transformation to lower temperatures (ΔT = 129 K), whereas the martensite develops into NM (Co) and 6 M (Fe & Cu) structures offering up to 13.9% theoretical strain (Co; NM). The Ni45Fe5Mn44Sn6 alloy is singled out by non-uniform composition; i.e. the γ phase coexists with 6 M martensite, and a ferromagnetic order setting in below 301 K, whereas all other alloys are chemically homogenous and predominantly paramagnetic. The results qualify the studied alloys as interesting candidates for high temperature shape memory alloys applications.

The magnesium alloy ZRE1 (2.7%Zn, 0.53%Zr, 3,14% rare earth elements) was applied as a matrix of composite reinforced with glassy carbon particles obtained by hot pressing of powder mixture. An influence of matrix chemical composition on interaction processes occurring at the interface was analyzed. The interface microstructure was characterized by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). It was revealed the continuous bonding between components and a presence of zone enriched with zirconium, rare earth elements and oxygen in comparison to the matrix composition.

The influence of Al substitution for Sn in Ni44Mn43.5AlxSn12.5-x(x= 0, 1, 2, 3) ferromagnetic shape memory alloy ribbons on phase transformation and microstructure evolution is outlined in this paper. Ribbons produced by melt spinning technique showed fully crystalline structure, however non uniform. Energy dispersive spectroscopy microanalysis (EDS) confirmed the average composition of ribbons in accord with the initial alloys. The higher symmetry parent phase was identified with the aid of X-ray diffraction (XRD) as bcc L21Heusler type structure. The unit cell parameters were determined applying the XRD profile fitting method. It was observed that with increase of Al content unit cell parameters and in turn unit cell volume decrease. This may be attributed to the fact that Al has a smaller radius compared to Sn, which it was substituted for. Differential scanning calorimetry (DSC) measurements did not allow to detect the martensitic transformation above -150°C.

Commercial brass Ms36, 2mm thick was annealed and deformed in 6 passes in dual rolls equipment with attached equal channel equipment (DRECE). Then, material was deformed again using constrained groove pressing (CGP) by pressing of grooves 4.2 mm thick, and the groove angle of 45 deg. The experiment was performed 8 times (pressing out grooves and straightening at room temperature). Both methods allowed deformation without changing of the thickness of the sample, which was almost constant near 2 mm. The tensile experiment have shown the Yield Strength YS after 8x groove pressing of 210 MPa and Ultimate Tensile Strength UTS increased 27% up to 430 MPa. At the same time total elongation decreased from 34 to 15 %. The structure of the material after DRECE 6 passes was investigated using conventional TEM and have shown only rather uniform distribution of dislocations. After additional 8 groove pressing experiment, frequent, narrow deformation twins were observed accompanied by the formation of subgrains. Orientation imaging microscopy performed have shown average grain size after DRECE process near 5 μm, which decreased after 8 processes of groove pressing down to 2.9 μm. The fraction of low angle boundaries (below 5 deg) decreased after groove pressing down to 73% from 85% after DRECE process and annealing, while the fraction of high angle grain boundaries (>15 deg) increased after groove pressing up to 24% from 14%, however the total length of high angle boundaries increased more than 2 times since grain size decreased. The structure studies have shown rather mild effect on the grain refinement of both methods and they have to be modified to obtain material approaching nanosize range.

The alloys Al-12 wt % Zn-3 wt % Mg-1.5 wt % Cu with addition of Zr were melt spun and then hot pressed under 600 MPa pressure at 380 °C. Refinement of the microstructure and reduction of the volume fraction of the η (MgZn2) phase was observed in melt spun ribbon, as compared to the mould cast alloys. Good quality samples without pores and cracks obtained by hot pressing were composed of grains of size 0.2-0.5 µm. The particles of the η phase enriched in Zn, Mg and Cu were homogenously distributed in the matrix, while a few nanometres large precipitates of magnesium oxide were located at grain boundaries. Plate like precipitates of metastable h¢ phase appear after ageing at 120 °C and lead to microhardness increase up to about 195 HV as compared to 145 HV in pressed sample. Hot pressed ribbons showed compression strength of about 450 MPa which increased up to 630 MPa after ageing.

The concept to design a composite of the 7475 alloy strengthened with particles of an amorphous aluminum based alloy was studied in the present paper. Mechanical alloying (MA) process was applied to obtain amorphous structure of the powder of composition Al70Ni10Zr10Ti10 (in at%). Elemental powders of this composition were ball milled for 60 h in a planetary high energy mill using steel balls. The estimated mean size of powder particles below 10 μm was much smaller than that of the initial elemental powders. The mean value of the microhardness of the milled powder was 384 HV and was significantly higher than that of initial powders. The dominant presence of the amorphous structure was confirmed using DSC studies, in which crystallization peaks were observed above 400°C. X-ray diffraction (XRD) patterns after various milling times confirmed a partial amorphization of the material. Additionally, weak maxima of Al3Zr4 phase were identified. TEM studies of powders confirmed the formation of predominantly amorphous structure with some nanocrystalline inclusions of intermetallic phases identified as Al3Zr4, AlZr3, Al3Ni and Al3Ti. The amorphous powder was mixed (for a short time) with prealloyed 7475 alloy powder 40 h ball milled to obtain nanocrystalline grain size of powder’s particles. Powders were hot pressed in vacuum, below the crystallization temperature at 380°C and pressure of 600 MPa in order to preserve amorphous and nanocrystalline grain structure. SEM studies of the composite containing 1/3 ball milled 7475 alloy and 2/3 of the amorphous powder allowed identifying low porosity and clean interface within the composite. The samples showed compression strength near 500 MPa and a few percent ductility. The cracks nucleated within the amorphous particles as resulted from SEM studies of the compressed samples.

The rapid solidification of Al-12 Zn-3 Mg-1.5 Cu (in mass%) alloy was investigated in order to determine structure changes and the effect of Zr or Sc+Zr additions. Rapidly solidified ribbons with the thickness of 30–50 mm were obtained by a melt spinning technique. The alloys cast into a copper mould were used as a reference material. The mould cast alloys as well as the melt spun ribbons revealed the dendritic microstructure of(Al) solid solution and (MgZn2) phase in the interdendritic areas. Additionally the T-Mg32(Zn, Al)49 phase with icosahedral quasicrystalline symmetry was found in the form of small particles located mainly at the wheel side in the Zr or Zr+Sc containing ribbons. The refinement of the microstructure and the reduction of volume fraction of the phase was observed in the ribbons. Large Al3Zr primary precipitates were observed in the mould cast alloy containing zirconium, while almost whole Zr in the ribbons dissolved in the aluminium solid solution. Annealing of ribbons at 400 � C led to the precipitation of spherical L12-Al3Zr or Al3(Sc, Zr) particles, coherent with the matrix. They could be responsible for the improvement of properties of the aluminium alloys by the retardation of recrystallization and grain growth. Plate like precipitates of metastable 0 phase appeared after ageing at 120 � C and led to the increase of microhardness up to about 230 HV. [doi:10.2320/matertrans.MB201009]

Amorphous structure of Ti(25)Zr(17)Ni(29)Cu(29) composition was studied. Alloys were prepared either by rapid solidification using melt spinning or by high-energy ball milling. The composition of multi-component eutectic in slowly cooled samples of ZrNiTiCu alloy was determined using EDS measurements in scanning microscope of slowly cooled cast samples. The alloys of eutectic composition were melt-spun or ball-milled. Transmission electron microscopy (TEM) studies of melt-spun ribbons from alloys near eutectic composition did not show presence of nanocrystals within the amorphous structure. TEM studies of ball-milled powders showed presence of nanocrystallites of size 2-5 nm. The electron diffraction pattern showed intense diffused ring due to the presence of the amorphous phase and a weak spot due to crystalline phases which were difficult to identify. The high temperature high-pressure compaction in vacuum of amorphous ball-milled powders resulted in a similar structure like in the powders showing nanocrystals embedded in the amorphous matrix. The crystallites were imaged using HREM. Interplanar distances were measured in pictures obtained by inverse fast Fourier transform (IFFT) of atomic planes to obtain better contrast. Analysis of the IFFT from high-resolution micrographs allowed to identify Cu(10)Zr(7) phase. Point analysis and elemental mapping performed using nondispersive X-ray energy spectroscopy showed uniform elements distribution indicating that chemical segregation to nanocrystals is within measurement error.

Powder metallurgy technology was elaborated for consolidation of shape memory NiTi powders. The shape memory alloy was compacted from the prealloyed powder delivered by Memry SA. The powder shows Ms = 10°C and As = -34°C as results from DSC measurements. The samples were hot pressed in the as delivered spherical particle's state. The hot compaction was performed in a specially constructed vacuum press, at temperature of 680°C and pressure of 400 MPa. The alloy powder was encapsulated in copper capsules prior to hot pressing to avoid oxidation or carbides formation. The alloy after hot vacuum compaction at 680°C (i.e. within the B2 NiTi stability range) has shown similar transformation range as the powder. The porosity of samples compacted in the as delivered state was only 1%. The samples tested in compression up to e = 0.06 have shown partial superelastic effect due to martensitic reversible transform- ation which started at the stress above 300 MPa and returned back to e = 0.015 after unloading. They have shown also a high ultimate compression strength of 1600 MPa. Measurements of the samples temperature changes during the process allowed to detect the temperature increase above 12°C for the strain rate 10-2 s-1 accompanied the exothermic martensite transformation during loading and the temperature decrease related to the reverse endothermic transformation during unloading.

The microstructure of Co 35+x - Ni 40-x - Al 25 (x = 0, 2.5, 5.0) ferromagnetic shape memory alloys annealed at 1200°C and water quenched has been investigated by optical (OM) and analytical transmission electron microscopy (TEM). The microstructure consists of elongated grains of martensite and 7 phase. Annealing twins were found frequently in the 7 phase. The volume fraction of γ phase has been determined to be about 40%. TEM observations show twinned L1 0 martensite with {111}-type twinning plane and tetragonality c/a = 0.85 in all investigated alloys. Determination of the composition of β phase, allows to calculate Al/Co and e/a ratio in the range 7.68-8.40 in correlation with its Ms temperatures between 66 and 167 °C, respectively. An increase in the Al/Co ratio together with a decrease of Ni content in β phase causes a decrease of the e/a ratio, which promotes a decrease of martensitic transformation temperatures.

The effect of increased Ta and Nb additions on the structure of high energy ball milled Ti alloys was studied using X-ray diffraction and high resolution TEM. Ball milled powders were consolidated using ultra high pressure from 4-7 GPa at temperatures of 650-700°C. The microstructure of the compacts consisted of ultra fine grains in the range of 20 nm of a and β phases. Micro-hardness measurements showed very high hardness of ball milled and compacted powders close to 7 GPa (slightly decreasing with the increase of alloying additions) and a decrease in the Young's modulus with the increase of Nb and Ta content i.e. the amount of β phase.

Molybdenum silicides were obtained by the self-propagating synthesis (SHS) method. Diamond composites containing 30 mass% of MoSi2 or Mo5Si3 bonding phase had been prepared using HT-HP Bridgman type apparatus. Sintering of the diamond composites were carried out at 2073±50 K and 8±0.2 GPa. The interactions in diamond-silicide composites were studied by means of X-ray diffractometry and transmission electron microscopy (TEM). Results of both mechanical properties and thermal resistance measurements are reported. Hardness HV1 for the composite with the predominantly MoSi2 bonding phase was found to be around 42 GPa. After heat treatment in 1200 °C for 30 min. in vacuum HV1 decreases to 29 GPa. In the second composite containing the Mo5Si3 bonding phase the HV1 of 28.0 GPa after thermal exposure changes to 21.0 GPa.

The TiAl-V alloys compositions were chosen from the γ-phase stability region up to maximum 20 at. % vanadium. The elemental powders were initially blended to desired composition of Ti-52.7Al-5V, Ti-55.4Al-10V, Ti-57.7Al-15V and Ti-60.4Al-20V (numbers indicate at. %). The milling was performed in a high energy planetary mill Fritsch Pulverisette P/4 resulted in formation of the almost fully amorphous structure after 40 hours. The formation of Al(Ti, V) solid solution was observed after 20 hours of milling. Longer milling caused amorphization of most of the material and formation of metastable phase in the alloy with the highest content of vanadium. TEM observation of powders after 40 hours of milling allowed to identify 50 nm wide nano-layers within individual particles. The origin of layered structure was explained as resulting from the mechanical alloying process, not from the thin foil preparation. The electron diffraction and bright field techniques revealed the amorphous and partially nanocrystalline structure within milled powders. Uni-axial hot pressing at 700°C under 200 MPa of milled powders allowed to obtain a bulk samples with density of about of 94 % of theoretical one. The X-ray diffraction revealed the two phases γ+α 2 structure. TEM studies have shown the nanometer range grain size structure with a mean size of about 20-30 nm. The diffraction pattern appeared in a ring like pattern without preferred pattern orientation. Some larger grains has shown a parallel aligned defects causing streaks in the diffraction indicating basal Ti 3 Al plane defects. Their existence indicate disordering within intermetallic grains in spite of 700°C annealing.

The Ni–49.7Ti (at.%) alloy was prepared by mechanical alloying (MA) and different steps of milling were investigated. An almost fully amorphous alloy was obtained after 32 h of milling. After consolidation by uniaxial hot die pressing and annealing at 1000 °C for 28 h, a complicated multiphase structure composed of Ni3Ti, NiTi2 and NiTi phases was formed. The β-NiTi phase undergoes reversible thermoelastic martensitic transformation (MT) with Ms temperature as high as 172 °C. This phenomenon was explained by Fe and Cr solute content introducing during milling and formation of the 4H martensite structure. The structure observations performed using scanning electron microscopy allowed to conclude that the average chemical composition of individual grains was Ti—49.7, Ni—47.76, Fe—2.54 (all in at.%). The second phase between the rounded β-NiTi grains was identified as the Ni3Ti phase and additionally, in some other places of the sample the Ni3Ti phase was also found. Transmission electron microscopy (TEM) of sintered samples confirmed the presence of 4H martensite within fine grains of the β-NiTi phase.

Porous Si (PS) has become an interesting material owing to its potential applications in many fields including microelectronics, optoelectronics and photovoltaics. PS layers on the front surface of n+/p monocrystalline, textured Si solar cells have been investigated with the aim of improving the performance of standard screen-printed cells, because an antireflection coating and a surface passivation can be obtained simultaneously in one chemical process. The results obtained could be useful in optimising the Si surface chemical treatment process. The surface morphology and microstructure of PS layers were investigated using SEM, TEM and non-contact AFM methods. The surface morphology of a PS layer depends strongly on the region where the pores are formed. The structure of PS layer is composed of macro-pores formed in p type Si (sizes vary over a large range up to 250 nm) and meso-pores formed in the n+ region of the p–n+ junction. The meso-pores of average size 20 nm on the pyramid slope elongate preferentially along the 〈111〉 direction. The interface between the PS layer and the substrate as well as the surface roughness are clearly defined. The results show that the PS layer on the pyramids is formed uniformly along the walls. Meso-pores created on the macro-pore surface are a characteristic feature of the surface between pyramids. Such a surface modification allows improving the Si solar cell characteristics.

Structural changes of melt-spun ribbons and mechanically alloyed AgCuCd alloy powders of ternary eutectic composition 17 wt.% Ag, 29.5 wt.% Cu and 53.5 wt.% Cd were studied using X-ray diffraction, and transmission and scanning electron microscopy. The equilibrium eutectic consists of α, β and γ phases. Rapidly quenched ribbon consists of metastable β(AgCd) phase showing B2 ordering with modulations following the 〈100〉 direction originating from spinodal decomposition. A small fraction of a fine mixture of randomly oriented α and γ crystallites (about 40 nm in size) with large β inclusions was found in very thin areas transparent for the transmission electron microscope observations. Fine globular clusters of γ(Ag, Cu) 5 Cd 8 precipitates of the same crystallographic orientation as the β matrix were observed in thicker areas. The mechanical alloying of mixed powders caused both formation of supersaturated α solid solutions after 32 h of milling and secondary crystallisation of γ(Ag, Cu) 5 Cd 8 and β 2 (Cu 2 Cd) phases after 64 h of milling. A decrease of the amount of initial elements is accompanied by refinement of its grain size. Transmission electron microscopy observations performed using the samples milled for 32 and 64 h revealed the nanocrystalline structure of α solid solution and γ and β 2 particles of about 15 nm size.

We have tested titanium (Ti) plates that are used for bone reconstruction in maxillofacial surgery, in combination with five types of novel long-resorbable biomaterials: (i) PCL0&mdash, polycaprolactone without additives, (ii) PCLMWCNT&mdash, polycaprolactone with the addition of multiwall carbon nanotubes (MWCNT), (iii) PCLOH&mdash, polycaprolactone doped with multiwall carbon nanotubes (MWCNT) containing &ndash, OH hydroxyl groups, (iv) PCLCOOH&mdash, polycaprolactone with the addition of multiwall carbon nanotubes (MWCNT) containing carboxyl groups, and (v) PCLTI&mdash, polycaprolactone with the addition of Ti nanoparticles. The structure and properties of the obtained materials have been examined with the use of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and/or X-ray powder diffraction (XRD). Titanium BR plates have been covered with: (i) PCL0 fibers (PCL0BR&mdash, connection plates), (ii) PCLMWCNT fibers (PCLMWCNTBR&mdash, plates), (iii) PCLOH fibers (PCLOHBR&mdash, plates), (iv) PCLCOOH (PCLCOOHBR&mdash, plates), (v) PCLTI fiber (PCLTIBR&mdash, connection plates). Such modified titanium plates were exposed to X-ray doses corresponding to those applied in head and neck tumor treatment. The potential leaching of toxic materials upon the irradiation of such modified titanium plates, and their effect on normal human dermal fibroblasts (NHDF) have been assessed by MTT assay. The presented results show variable biological responses depending on the modifications to titanium plates.