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This paper is the review of our study published earlier in Acta Phys. Polon. A 121, 522 (2012) [7], Phys Lett A 378, 1364 (2014) [25], and [1]. It’s aim is to pay attention to the new possibilities related to producing the new types of THz generators. The suggested effects are the result of combining two effects: Gunn-effect in a material such as GaAs and undulator-like radiation, or 'pumping wave' acting on the electrons which is the result of undulator field, while the second is the backward effect of radiation which is produced by electrons moving within such a micro-undulator. It is very probable that the effects can be used to develop a new semiconductor-based room temperature source of the THz-radiation.

Brain activity determines which relations between objects in the environment are perceived as differences and similarities in colour, smell, sound, etc. According to selectionism, brain activity does not create those relations; it only selects which of them are perceptually available to the subject on a given occasion. In effect, selectionism entails that perceptual experience is diaphanous, i.e. that sameness and difference in the phenomenal character of experience is exhausted by sameness and difference in the perceived items. It has been argued that diaphaneity is undermined by phenomenological considerations and empirical evidence. This paper considers five prominent arguments of this sort and shows that none of them succeeds.

The study of the fundamentals of the α → ω and β → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Prior to HPT, three alloys with 5, 10, and 20 wt% of Nb were annealed in the temperature range of 700–540°C in order to obtain the (α + β)-phase state with a different amount of the β-phase. The samples were annealed for a long time in order to reach equilibrium Nb content in the α-solid solution. Scanning electron microscope (SEM), transmission electron microscopy, and X-ray diffraction techniques were used for the characterization of the microstructure evolution and phase transformations. HPT results in a strong grain refinement of the microstructure, a partial transformation of the α-phase into the ω-phase, and a complete β → ω phase transformation. Two kinds of the ω-phase with different chemical compositions were observed after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the almost Nb-pure α-phase. It was found that the α → ω phase transformation depends on the Nb content in the initial α-Ti phase. The less the amount of Nb in the α-phase, the more the amount of the α-phase is transformed into the ω-phase.

According to unconscious perception hypothesis (UP), mental states of the same fundamental kind as ordinary conscious seeing can occur unconsciously. The proponents of UP often support it with empirical evidence for a more specific hypothesis, according to which colours can be seen unconsciously (UPC). However, UPC is a general claim that admits of many interpretations. The main aim of this paper is to determine which of them is the most plausible. To this end, I investigate how adopting various conceptions of colour and perceptual phenomenal character affects UPC’s resilience to objections. This brings me to the conclusion that the most plausible reading of UPC is the one according to which the phenomenal character of colour perception (i) is constituted by colours qua primitive mind-independent qualities of the environment and (ii) is not essentially tied to consciousness. My conclusion not only identifies the most plausible interpretation of UPC, but also highlights and supports an unorthodox version of the relational theory of perception, which is a perfectly viable yet so far overlooked stance in the debate about unconscious perception.

The high-pressure torsion (HPT) of binary copper alloys with 3, 5, 8, 10 wt. % Ag and 14 wt. % Sn has been studied at room temperature THPT. Before HPT, the Cu–Ag alloys have been annealed at 12 different temperatures between 320 and 800 °C and Cu–14 wt. % Sn has been annealed at 9 different temperatures between 310 and 500 °C. Thus, before HPT the Cu–Ag alloys consisted of Ag-particles in the Cu-based matrix with silver content cinit from almost zero to 8 wt.%. The Cu–14 wt. % Sn samples had Cu-based matrix with tin concentration cinit from almost zero to 14 wt.% Sn and precipitates of e or δ Hume-Rothery intermetallic phases. After about 1.5 plunger rotations a certain steady-state concentration css of the alloying element is reached in the matrix. The measured css values were 5.5±0.1 wt. % Ag and 13.1±0.1 wt. % Sn. If the initial concentration cinit in Cu matrix was below css (cinit css it decreased towards css. We observed that css did not depend on cinit in broad interval of cinit and was, therefore, equifinal. The equifinal css values corresponded to the certain equilibrium solubilities of silver and tin in Cu matrix and allowed to estimate the (elevated) effective temperature as Teff (Ag) = 700±10 °C and Teff (Sn) = 400±10 °C, respectively. The observed phenomena are discussed using the ideas of non-equilibrium thermodynamics of open systems. During HPT the decomposition of a solid solution competed with dissolution of precipitates. As a result, a dynamic equilibrium established between precipitation and dissolution at steady-state deformation stage. In this dynamic equilibrium a certain steady-state concentration css of the alloying element is reached in the matrix. In Cu-based alloys, the obtained Teff is always higher than THPT and correlates with activation enthalpy of dopant diffusion in Cu. Other HPT-driven phenomena such as accelerated mass transfer, intermetallic phase formation, grain boundary faceting and grain boundary segregation are taken into account to evaluate the effective temperature Teff.

The fundamentals of discontinuous precipitation (DP) reaction modelling using a cellular automata (CA) method are presented. In the proposed CA model, cell states, internal variables, equations, and transition rules were defined to predict the manner of mass transport during DP reaction and to relate changes in the microstructure with corresponding changes in chemical composition. Furthermore, the concept of digital material representation (DMR) was introduced into the CA model, which allowed schematic images of the microstructure to be used as starting structures in the modelling of the DP reaction. The preliminary assumptions adopted in the proposed CA model for the DP reaction were verified by numerical simulations of the growth of discontinuous precipitates at a steady-state at the example of Al-22 at.% Zn alloy. The outcomes achieved from the CA simulations were presented in a different form than that most commonly used previously (single concentration profiles), namely as the 2D maps showing changes in Zn content accompanying the successive stages of growth of discontinuous precipitates. The model used for the description of the solute diffusion along of the reaction front (RF) allowed two-dimensional systems at the nano-scale to be treated within a reasonable simulation time. The obtained results indicate that the developed CA model was able to realistically simulate the DP reaction, which was confirmed by the visualisation of migrating RFs together with associated chemical composition changes in the microstructure.

Severe plastic deformation (SPD) can induce various phase transformations. After a certain strain, the dynamic equilibrium establishes between defects production by an external force and their relaxation (annihilation). The grain size, hardness, phase composition etc. in this steady-state does not depend on the initial state of a material and is, therefore, equifinal. In this review we discuss the competition between precipitation and dissolution of precipitates, amorphization and (nano)crystallization, SPD-induced accelerated mass-transfer, allotropic and martensitic transitions and formation of grain boundary phases.

During high-pressure torsion (HPT) the dynamic equilibrium establishes with a certain steady-state composition of the solid solution along with the grain refinement by a factor of more than thousand. The formation of such HPT steady-state in copper alloys with Co, Ag and In has been studied. If precipitates of a second phase were present in the sample before HPT, their dissolution led to the enrichment in the (Cu) matrix solid solution. If precipitates of a second phase were absent, the HPT led to the depletion in the (Cu) matrix due to the segregation in newly formed defects like grain boundaries.

Phase transformations of some Hume-Rothery phases (electron compounds) to others in a copper-tin system subjected to high-pressure torsion were detected in our previous work [B.B. Straumal et al., JETP Lett. 100, 376 (2014)]. In particular, the torsion of the ζ + e phase mixture at high pressure led to the formation of the δ + e phase mixture, as after long-term annealing in the temperature interval Teff = 350–589°C. In this work, it has been shown that the high-pressure torsion of α-solid solutions of tin in copper results in the final stable solid solution whose composition is independent of the composition of the initial α phase before high-pressure torsion. The final composition is the same as after long-term annealing at the temperature Teff = (420 ± 10)°C. The rate of high-pressure torsion-induced mass transfer is several orders of magnitude higher than the rate of conventional thermal diffusion at the treatment temperature THPT and is close to values at Teff. This occurs because high-pressure torsion increases the concentration of lattice defects and this increase is in turn equivalent to an increase in the temperature.

The influence of high pressure torsion (HPT) on the formation and decomposition of solid solutions in the copper–silver system has been studied. The investigated Cu-8 wt.% Ag alloy was annealed at two different temperatures, 500 and 650°C, and quenched. The samples consisted of (Cu) solid solution in the matrix with (Ag) precipitates. During HPT a steady-state value of torsion torque was reached after about 1.5 anvil rotations. After HPT (5 anvil rotations) the composition of the (Cu) solid solution in both samples had become equal. In other words, the concentration of silver in the (Cu) matrix annealed at 650°C decreased and in the sample annealed at 500°C increased. Moreover, a similar process took place in (Ag) precipitates as well. The concentration of copper in (Ag) particles in the sample annealed at 650°C decreased and in the sample annealed at 500°C increased. Thus, the composition of (Cu) and (Ag) solid solutions reached at steady-state during HPT does not depend on that before HPT. The composition of the (Cu) and (Ag) solid solutions after HPT is as high as if the samples were annealed at a certain intermediate temperature about 600 ± 20°C.

This paper is the review of our study published in J Appl Phys 115, 233509 (2014) and J Mater Sci 53, 2034 (2018). In it, we examined the possibility of fabricating the metamaterial, which is both gyrotropic and of the simultaneously negative permittivity and permeability. Our idea was to use the three-component mixture of ingredients, where one of them is responsible for the negative effective permeability µeff of hypothetical metamaterial, while all three are responsible for the negative value of effective permittivity εeff. At first we considered the following composite: the first component was the “swarm” of single-domain ferromagnetic nanoparticles, immersed in a mixture of other two, silver and mercury cadmium telluride. Then, as fabrication of the Hg1-x Cdx Te is related to using mercury which is very poisoning, we tried to exclude this material substituting it by Pb1-x Snx Te. Additionally, taking into account that silver is relatively expensive material, we have also used Cu and Al particles as the cheaper substitute of it. We have shown by computer simulations that by the proper fitting of the parameters, e.g., the radius of nanoparticles, their magnetic moments, the relative concentration of ingredients, etc., it is possible to obtain the double-negative metamaterial, that is with negative refraction index in a relatively broad range of temperatures and magnetic fields. The last seems to be very promising in terms of practical applications of metamaterials.

The dissolution process of a lamellar structure with α and Γ phases formed during a discontinuous precipitation reaction is investigated here with a Fe-13.5 at. % Zn alloy by means of optical microscopy and scanning and transmission electron microscopy. The α phase is a solute-depleted solid solution and the Γ phase is the intermetallic compound Fe3Zn10. The examination reveals that the dissolution occurs in a discontinuous mode by a receding of the former reaction front of the discontinuous precipitation towards the position of the original grain boundary. A new solid solution in the post-dissolution area is especially inhomogeneous and reflects the former locations of the Γ lamellae (“ghost images”) and the receding reaction front (“ghost lines”). A simulation procedure is applied to determine the Zn concentration profiles left in the post-dissolution region. Their shapes are mostly affected by the Zn content at the positions where the Γ lamellae have just been dissolved, which was also confirmed by the quantitative microchemical analysis.

This paper discusses the features of ω-phase formation and its thermal stability depending on the phase composition, alloying element and the grain size of the initial microstructure of Ti–Nb and Ti–Mo alloys subjected to high-pressure torsion (HPT) deformation. In the case of two-phase Ti–3wt.% Nb and Ti–20wt.% Nb alloys with different volume fractions of α- and β-phases, a complete β→ω phase transformation and partial α→ω transformation were found. The dependence of the α→ω transformation on the concentration of the alloying element was determined: the greater content of Nb in the α-phase, the lower the amount of ω-phase that was formed from it. In the case of single-phase Ti–Mo alloys, it was found that the amount of ω-phase formed from the coarse-grained β-phase of the Ti–18wt.% Mo alloy was less than the amount of the ω-phase formed from the fine α′-martensite of the Ti–2wt.% Mo alloy. This was despite the fact that the ω-phase is easier to form from the β-phase than from the α- or α′-phase. It is possible that the grain size of the microstructure also affected the phase transformation, namely, the fine martensitic plates more easily gain deformation and overcome the critical shear stresses necessary for the phase transformation. It was also found that the thermal stability of the ω-phase in the Ti–Nb and Ti–Mo alloys increased with the increasing concentration of Nb or Mo.

The growth of lamellar structure during discontinuous precipitation occurs frequently by so-called go-and-stop fashion. The results of simulation combined with the changes of Cahn’s parameter C revealed two types of such motion. The process takes place in the successive stages which can be distinguished judging from the value of C parameter. For lower values of linear growth rate (v = 10÷20 nm/s) and smaller α lamella thickness (100÷200 nm), the full cycle with relaxation takes 4–6 s. The faster movement of the reaction front (v = 30 nm/s) resulted in dramatic decrease of the full cycle to τtotal = 0.8 s. The same behavior is observed if the α lamella thickness increases beyond 200 nm at constant v equal to 10 nm/s. Both predicted types of go-and-stop motion can experimentally be observed during growth or dissolution of discontinuous precipitates. What is the reason that particular type prevails is unknown, and this is invitation for further studies especially using high-resolution transmission electron microscope operating in in situ mode.

Potential impact of copper replacing silver in the paste used for the front electrode fabrication in crystalline silicon solar cells was investigated. The copper was applied as a new CuXX component with about 2 wt.% to 6 wt.% share of XX modifier. The generated CuXX molecules were analyzed using transmission microscopy. Based on the commercial Du Pont PV19B paste, CuXX and XX materials, the new PV19B/CuXX paste with 51 wt.% share of Cu and the PV19B/XX paste with 51 wt.% share of XX only were developed. Comparative studies of the effect of the commercial PV19B paste made by DuPont Company, and the pastes with the CuXX component and with the modifier XX alone on the electrical parameters of solar cells produced on crystalline silicon were carried out. The solar cells were characterized by the current-voltage technique. As a final result, the Cz-Si solar cell with the 51 wt.% share of Cu in the front electrode having a series resistance of 0.551 Ω·cm2, an efficiency of 14.08 % and, what is more important, the fill factor of 0.716, was obtained. It is the best result ever obtained concerning direct Cu application for solar cells fabricated in thick-film technology.

The influence of Zn-concentration gradient on the occurrence of discontinuous precipitation has been analyzed in a Fe-13.5 at.% Zn alloy using the simulation method and Cahn′s diffusion model. The results have shown that the reaction front (RF) movement takes place by go- and -stop fashion accompanied by appropriate changes of Cahn′s parameter reaching maximum values, Cmax at the end of go- period. Then, the value of C decreases enabling relaxation of the RF and beginning of the next go- event. In this way, the simulation is the only one source of data showing how the solute concentration across the α phase lamella changes during the stop- period of the growth of discontinuous precipitates. The smaller thickness of the α phase lamellae and larger Cmax, the longer whole go- and –stop cycle, but not exceeding few seconds. The distance of RF movement is characterized by certain optimum value which is close to v = 45 nm/s regardless of the value of α phase lamella thickness.

Through-hole technology (THT) for the electronic circuits assembly is known for decades and recently is replaced by surface-mount technology (SMT). However, THT method is still widely used in many modern devices, where proper power dissipation is essential. The design for manufacturing (DFM) rules is important for the high reliability of the THT products. The experiment was performed for the various solder lands and hole sizes and two solder materials (lead-free solder Sn3Ag0.5Cu and Sn37Pb) on the printed circuit board (PCB) with the hot air solder leveling finish (HASL), specially designed for this purpose. The various types of THT electronic components were connected in the wave soldering process. Next, the PCB were subjected to the thermal cycles test (550 cycles from −20 °C to +80 °C) to verify the reliability of the solder joints under the extreme working conditions. The scanning electron microscopy (SEM) technique combined with an energy dispersive X-ray spectroscopy (EDS) allowed revealing the microstructure and chemical composition details of the obtained interconnections before and after the thermal tests.

Severe plastic deformation not only leads to grain refinement but also accelerates mass-transfer and drives phase transformations in these Cu-based alloys. This review is devoted to the dynamic equilibrium between decomposition of (supersaturated) solid solution and dissolution of precipitates during high pressure torsion (HPT) of diluted Cu-based Cu–X alloys. The precipitation of second phase particles from a solid solution and their dissolution take place simultaneously and compete with each other. During HPT, a certain steady-state concentration C s of a second component in a solid solution is reached, as if a sample would be annealed at a certain effective temperature T eff . We found that T eff linearly increases with increase of activation enthalpy of bulk tracer diffusion H D . The correlation between activation enthalpy of bulk tracer diffusion H D and melting temperature T m of diffusing alloying component has been found for the first time. As a result, T eff linearly increases with increase of melting temperature T m of diffusing alloying component as well. The observed correlations allow one for the first time to predict the behaviour and phase transitions in the Cu-based alloys under high pressure torsion.

The discontinuous precipitation (DP) belongs to a group of diffusive solid state phase transformations during which the formation of a new phase is heterogeneous and limited to a migrating reaction front (RF). The use of analytical electron microscopy provided reliable information that there is no differences in the diffusion rate at the stationary grain boundary and moving RF of DP reaction. On the other hand, the use of “in situ” transmission electron microscopy observations indicated the importance of stop-go motion or oscillatory movement of the RF.During 2004-2016 period more or less 280 papers were published in which the terms “discontinuous precipitation, “cellular precipitation”, discontinuous coarsening” appeared either in the abstract or in key-words.In the present contribution, the research on the DP reaction will be reviewed taking into account new aspects of theories and modelling, new evidences and findings, effect of various factors including third element, external stresses, plastic deformation and GB orientation, occurrence in less known systems and alloys like: superalloys, nitrided Fe-based alloys and Cu-based alloys. Finally, some suggestions for the future research will be formulated.

Cu–14 wt% Sn alloy was annealed at temperatures of 320 and 500 °C. The concentration of tin cinit in the copper-based matrix increased with annealing temperature. The annealed samples were subjected to high-pressure torsion (HPT) at 6 GPa, 5 turns, 1 rpa. HPT led to the refinement of Cu grains. The shape of the colonies of α + ε phases changed only slightly. The HPT-driven enrichment of the Cu-based solid solution with Sn atoms cHPT–cinit decreased with increasing cinit. The performed theoretical analysis explained this behavior of the HPT-driven enrichment.

It is well known that severe plastic deformation not only leads to strong grain refinement and material strengthening but also can drive phase transformations. A study of the fundamentals of α → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Before HPT, a Ti–3wt.%Nb alloy was annealed at two different temperatures in order to obtain the α-phase state with different amounts of niobium. X-ray diffraction analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for the characterisation of phase transitions and evolution of the microstructure. A small amount of the β-phase was found in the initial states, which completely transformed into the ω-phase during the HPT process. During HPT, strong grain refinement in the α-phase took place, as did partial transformation of the α- into the ω-phase. Therefore, two kinds of ω-phase, each with different chemical composition, were obtained after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the α-phase. It was also found that the transformation of the α-phase into the ω-phase depended on the Nb concentration in the α-Ti phase. The less Nb there was in the α-phase, the more of the α-phase was transformed into the ω-phase.

The Ti–3.3 at.% Co was annealed at three different temperatures (400, 500 and 600 °C) in order to obtain (α + Ti2Co) state with different concentrations of cobalt in the α-phase and the different volume fractions of Ti2Co intermetallic particles. Next, the alloy was subjected to high pressure torsion (HPT) at room temperature. The deformed alloy was studied using X-ray diffraction, scanning and transmission electron microscopy. This showed strong microstructure grain refinement, fragmentation and partial Ti2Co intermetallic phase dissolution, along with α → ω phase transformation. The volume fraction of the ω-phase depends strongly on the cobalt content in the initial α-matrix and the morphology of the α- and Ti2Co phases. The thermal stability of the ω-phase was studied using calorimetric and in situ XRD measurements. It was found that the alloying of titanium with 3.3 at.% of cobalt results in a significant increase of the volume fraction of the ω-phase and its thermal stability from 180°С to 415°С in comparison to pure titanium.

Diffusion-controlled interaction of pure Cu with Sn at 488 K results in the formation of e-Cu3Sn and η-Cu6Sn5 intermetallic compounds, and small additives of Ni in the Cu-substrate (up to 1 at. %), do not influence phase composition of the diffusion zone. It was found that in the η-phase, Sn diffuses somewhat faster than Cu (and Ni) does, and diffusion porosity is developed in the vicinity of the substrate/reaction product interface. When a Cu–Ni alloy containing (5–25) at. % of Ni is involved in the interaction at 488 K, no e-phase is formed and no pores can be found in the vicinity of the reaction interface. In these couples, ThO2-particles introduced as fiducial markers at the contact surface, end up after the interaction inside the (Cu,Ni)6Sn5 product layer close to the interface with Sn. The reaction layer growth follows a parabolic kinetics, and the growth rate of the (Cu,Ni)6Sn5 product in the Cu1-xNix/Sn (x = 0.05–0.25) couples is much higher than that of η-phase in binary Cu/Sn and ternary couples with lower Ni-content. TEM investigation revealed that reaction product in the Cu25Ni/Sn couple consists of domains of differently oriented unit cells of long-period superlattice formed in the (Cu,Ni)6Sn5 phase. In each domain, there is a periodic array of antiphase boundaries which provide a high density of short-circuit paths for diffusional transport resulting in the fast growth kinetics of the product intermetallic layer.

The Cu–36 wt% Sn alloy was subjected to the high pressure torsion (HPT) at room temperature. Before deformation the microstructure was composed of alternating coarse-grained plates of the ζ and e compounds (Hume-Rothery electronic phases). HPT led, as usual, to the strong grain refinement and increase of dislocation density. However, the macroscopic shape of ζ and e plates remained unchanged. It means that the refinement took place in each phase individually, i.e. inside the respective ζ and e plates. High angle grain boundaries are more pronounced in e phase. This unusual behavior of the alloy is connected with a high hardness of the ζ and e intermetallic compounds.

The microstructure and phase composition of Ni-P and Ni-P-Re layers with medium phosphorus content of 8.8 and 8.2 wt. % of P, respectively, and 6.8 wt.% of Re electroless plated on copper substrate were studied. Both of the deposits showed amorphous X-ray profile, however, as it was expected, the presence of small (about 10 nm in size) nanocrystallites was observed in both kinds of plating under transmission electron microscope (TEM). The crystallization temperatures, measured in the range of 298–773 K, significantly increased with rhenium content as well as with increasing heating rate and differed by about 40 K. The activation energy calculated based on the Kissinger’s model in the case of Ni-8.2P-6.8Re plating was 217.7 kJ mol−1 and for Ni-8.8 P was 206.3 kJ mol−1. X-ray diffraction (XRD) measurements of the Ni-P deposits carried out after the heat treatment indicated the presence of the Ni and Ni3P phases, which was confirmed by electron diffraction and high resolution observations in TEM. XRD data concerning Ni-P-Re plating revealed the following phases: Ni, Ni3P, Ni0.21Re0.79, Ni5P2 and NiP, while TEM investigation confirmed the presence of Ni3P, NiP, Ni5P2 so far. Due to the very local information gathered from the TEM, this result needs further studies.

Two copper alloys with 7.8 and 23 at.% tin with different content of e Hume Rothery phase were subjected to high pressure torsion (HPT) at room temperature. The initial state of both alloys before HPT was quite different. The first alloy contained the Cu matrix (α-phase) with uniformly distributed precipitates of e-phase, while another consisted of alternating plates of the e phase and fine-grained (α + e) mixture. Strong grain refinement of α phase to the nanometer range and partial dissolution of e phase in Cu-matrix were observed in the Cu–7.8 at.% Sn alloy after HPT. The Cu–23 at.% Sn alloy after HPT revealed neither the grain refinement nor dissolution of phases.

Phase transformations induced by high pressure torsion (HPT) at room temperature in two samples of the Cu-0.86 at.% Cr alloy, pre-annealed at 550 °C and 1000 °C, were studied in order to obtain two different initial states for the HPT procedure. Observation of microstructure of the samples before HPT revealed that the sample annealed at 550 °C contained two types of Cr precipitates in the Cu matrix: large particles (size about 500 nm) and small ones (size about 70 nm). The sample annealed at 1000 °C showed only a little fraction of Cr precipitates (size about 2 μm). The subsequent HPT process resulted in the partial dissolution of Cr precipitates in the first sample and dissolution of Cr precipitates with simultaneous decomposition of the supersaturated solid solution in another. However, the resulting microstructure of the samples after HPT was very similar from the standpoint of grain size, phase composition, texture analysis and hardness measurements.

The paper presents a comprehensive study on the titanium and aluminum clads manufactured by explosive welding. Particularly, the microstructure evolution of the Al/Ti interface at 825 K and various annealing time was examined. In the state directly after explosive welding, the wavy morphology of the connection was locally composed of four intermetallic phases: TiAl3, TiAl2, TiAl and Ti3Al, forming small and peninsula-like morphology (vortex). The annealing process mainly caused growth of the TiAl3 phase as a continuous layer. The studies of the growth kinetics showed four stages: incubation period (up to 1.5 h), the growth govern by the chemical reaction (1.5–5 h), mixed mechanism of chemical reaction and volume diffusion and finally the volume diffusion growth (36–100 h). The orientation maps revealed significant differences concerning the microstructure and texture of welded metals. Directly after explosive welding process, aluminum possessed a typical rolled texture, while in titanium intensive twinning was observed. After annealing, due to the secondary recrystallization, abnormal grain growth was observed in aluminum, while in titanium annihilation of deformation twins took place. The hardness profile made across the welded area after annealing showed the highest values between 365–750 HV in vortex regions at the Al/Ti interface. Keywords: Explosive welding, Intermetallics, Titanium, Aluminum

The Ti–3.3 at.% Co alloy was annealed at 800 °C and then deformed by high-pressure torsion (HPT) at room temperature. The initial microstructure contains coarse grains of the α-phase uniformly distributed in the fine-lamellar (α+β) matrix. The study of the alloy after HPT by means of X-ray diffraction (XRD), scanning and transmission electron microscopy techniques showed strong grain refinement of the microstructure and the appearance of the high-pressure ω-Ti phase as the result of β→ω and partial α→ω phase transformations. It was found that the α→ω phase transformation depends not only on phase composition, but also on the shape and grains size as well (only fine lamellae of the α-Ti transformed into the ω-Ti phase). The formation of the ω-Ti phase doubled the hardness of the alloy. The thermal stability of the metastable ω-Ti phase, investigated by means of calorimetric and in-situ XRD measurements, increased from 180 °C to 375 °C in comparison to pure titanium.

High-pressure torsion has been used to obtain the ultra-fine grained (UFG) state with a high specific area of grain boundaries (GBs) in Al-Zn, Al-Mg, Cu-Ag, Cu-Co, and Cu-Ni solid solutions with face-centered cubic (fcc) lattices. The UFG samples were heated in a differential scanning calorimeter (DSC). Small endothermic peaks in the DSC curves were observed in the one-phase solid-solution area of the respective phase diagrams, i.e., far away from the bulk solidus and solvus lines. A possible explanation of these endothermic peaks is based on the hypothesis of phase transformations between GB complexions. This hypothesis has been supported by observations with transmission electron microscopy and electron backscattering diffraction. The new lines of GB phase transformations have been constructed in the Al-Zn, Al-Mg, Cu-Ag, Cu-Co, and Cu-Ni bulk phase diagrams.

The aim of this work was to study the influence of severe plastic deformation (SPD) on the dissolution of silver particles in Cu&ndash, 8wt.%Ag alloys. In order to obtain different morphologies of silver particles, samples were annealed at 400, 500 and 600 &deg, C. Subsequently, the material was subjected to high pressure torsion (HPT) at room temperature. By means of scanning and transmission electron microscopy, as well as X-ray diffraction techniques, it was found that during SPD, the dissolution of second phase was strongly affected by the morphology and volume fraction of the precipitates in the initial state. Small, heterogeneous precipitates of irregular shape dissolved more easily than those of large size, round-shaped and uniform composition. It was also found that HPT led to the increase of solubility limit of silver in the copper matrix as the result of dissolution of the second phase. This unusual phase transition is discussed with respect to diffusion activation energy and mixing enthalpy of the alloying elements.

Studies of the commonly used Ni-P surface finish of 4.3 and 11.6 wt. % of P content electroless plated on nickel substrates followed by their reaction with SAC305 solder were performed. It was demonstrated that the Ni-4.3P plating was crystalline, while the Ni-11.6P was mostly amorphous. The transformation of the Ni-P into Ni3P phase took place at 672 K and 605 K for low and high P amount, respectively. The activation energy (E a ) of the crystallization processes in the Ni-P plating was lower for the Ni-11.6P plating. Interaction of SAC305 solder with both types of the inspected plating showed the creation of (Cu,Ni)6Sn5 phase in the form of thin layer and large scallops, while for Ni-11.6P/SAC305 interface also (Ni,Cu)3Sn4 phase. The thickness of these phases was larger in the case of low phosphorous containing plating. The Ni-11.6P plating after the reaction with SAC305 totally transformed into Ni12P5, while the enrichment in P up to 10.5 wt. % occurred in the Ni-4.3P which did not lead to the appearance of any NixPy type phases. After the reaction of plating with solder the Ni2SnP phase was not identified. This was related to the absence of spalling phenomenon of the intermetallics into solder.

During severe plastic deformation (SPD), a steady-state is usually reached after a certain value of strain (i. e. number of passes during equal-channel pressing or number of rotations during high pressure torsion). The structure and properties of a material in a steady state (including composition of phases) do not depend on those in the starting state before SPD. In other words they are equifinal, and the production of lattice defects is in dynamic equilibrium with defect elimination. Moreover, the SPD-treatment at ambient temperature T SP D = 300 K is frequently equivalent to the heat treatment at a certain elevated temperature T eff > 300 K. For example, the composition of phases in Cu–Ni, Co–Cu and Nd–Fe–B-based alloys after high pressure torsion corresponds to the states at 200, 890 and 1 170 °C, respectively, and is rather insensitive to the high pressure torsion rate (between 0.2 and 2 rpm) and pressure (between 3 and 8 GPa).

Severe plastic deformation (SPD) can lead to the phase transformations in the materials. Even the SPD-treatment at ambient temperatureTSPD= 300 K is frequently equivalent to the heat treatment at a certain elevated temperature (effective temperature)Teff> 300 K. However, if the real annealing at effective temperature leads to the grain growth, SPD leads to strong grain refinement. SPD also accelerates the mass transfer in the materials. In this review the methods of determination for effective temperature after high-pressure torsion of metallic alloys are discussed as well as SPD-driven acceleration of diffusion.

High-pressure torsion of six homogenized Cu–In alloys (2.3 to 13.5 at. % In) with negative mixing enthalpy has been studied. The torsion torque reached a steady-state after 1–2 anvil rotations. Differently to the alloys with positive mixing enthalpy, the Cu(In) solid solution did not decompose. Moreover, the precipitates of δ-phase in the Cu–13.5 at. % In alloy partially dissolved and additionally enriched the Cu(In) solid solution.

It has been revealed experimentally that high-pressure torsion induces phase transformations of certain Hume-Rothery phases (electron compounds) to others. High-pressure torsion induces the ξ → δ + ɛ reaction in copper-tin alloys with the appearance of the δ + ɛ phase mixture as after long-term annealing in the temperature range T eff = 350–589°C. The mass transfer rate driven by high-pressure torsion is 14–18 orders of magnitude higher than the rate of conventional thermal diffusion at the processing temperature T HPT. This phenomenon can be explained by an increased concentration of defects (in particular, vacancies) in the steady state under high-pressure torsion, which is equivalent to an increase in the temperature.

In this paper the improving photovoltaic conversion efficiency of multicrystalline silicon solar cells obtained by acid texturization is presented. Different solutions from two various composition ranges of HF:HNO3:CH3COOH/H2O system were examined. The influence of the HF/HNO3 content, type of diluents and texturization process time on the basic optoelectronic parameters of multicrystalline solar cells was also studied. This research brings new experimental receipt which allows to obtain the proper surface morphology after the texturization in a very short time of 60 s. The optimal acid volume etching ratio was found to be HF:HNO3:H2O = 7:1:2. For the first time, etching lasting 1 min causes the lowering the reflectivity value below 12% and also improves the conversion efficiencyby22%inrelation to the reference sample without acid texture. The inverse HF/HNO3 ratio resulted in two times higher diameter of obtained rounded pits which allowed better coverage of the front metal grid patterning over the flat surface. Moreover, the higher reflectance value was accompanied by relatively high efficiency up to 13.9%.

High-pressure torsion of Cu–4.9 wt% Co alloy has been studied, with Co fully dissolved in the Cu matrix and fully precipitated from the matrix. A steady-state was reached in both samples after 1–2 anvil rotations. The solid solution in the first sample partly decomposed. The Co precipitates in the second sample partly dissolved in the matrix. In both cases the Co precipitates surrounded by the Cu-based solid solution with about 2.5 wt% Co were formed.

Severe plastic deformation can lead to the phase transformations in the materials. Even the severe plastic deformation at ambient temperature is frequently equivalent to the heat treatment at a certain elevated temperature (effective temperature). However, if the real annealing at the elevated temperature leads to the grain growth, the severe plastic deformation leads to strong grain refinement. In this review the methods of determination of effective temperature after high-pressure torsion of metallic alloys are discussed.

For the first time, the in-situ observation combined with Electron back scatter diffraction (EBSD) measurements were applied to discontinuous precipitation (DP) in the Al-22 at.% Zn alloy. So far, all the studies were restricted to “frozen” images of grain boundaries (GBs) after certain time of ageing. This did not allow the precise estimation of the incubation period preceding the initiation and growth discontinuous precipitates, as well it was not possible to distinguish still growing cells from those for which the growth was terminated. New approach permitted to determine that a large fraction of GBs does not undergo DP process. This was especially true for low angle GBs with misorientations below 19°. Growth in one direction occurred for a relatively large fraction of GBs. However, no correlation was found for the relationship between misorientation angle and growth rate on one and both sides of the GB as well for incubation period versus growth rate. Only few GBs were characterised with special CSL misorientation and they showed the growth in one direction with an exception of Σ3 grain boundary (no growth). Moreover, there was no evidence that the GBs close to the special Σ misorientations exhibited a very low DP reaction rate.

This work presents data on changes in the structure and properties of aluminum-based alloys subjected to severe plastic deformation by high-pressure torsion. Microstructure and the composition and change in temperature for phases are studied for double (Al-Zn, Al-Mg) and ternary (Al-Mg-Zn) alloys. Tie-lines of the liquid phase wetting of grain boundaries and grain boundary solvus lines are constructed on phase diagrams of our Al-Zn and Al-Mg systems. The shifting of the phase composition in the bulk of aluminum grains from the Al + τ region to the Al + η region of the Al-Mg-Zn phase diagram with an increase in the specific area of grain boundaries is described.

The microstructure and magnetic properties of binary Cu–Co alloys are studied. The investigations have been carried out using samples in two structural states, i.e. as-cast and after severe plastic deformation by the high-pressure torsion (HPT) carried out at the ambient temperature and pressure of 6 GPa. The grain size after HPT is in the nanometer range. HPT allows one to control the ratio between ferromagnetic and superparamagnetic precipitates in the diamagnetic matrix.

The microstructure and chemistry of the interface between SAC305 solder and electroless Ni–P coating (ENIG) was examined using scanning and transmission electron microscope equipped with an energy dispersive X-ray spectrometer. Four layers have been distinguished after 5 min of interaction at 503 K. There were: NiP-amorphous layer corresponding to Ni–P coating, Ni12P5 and Ni2SnP. The discontinuous Ni2SnP layer at SAC/ENIG interface was composed of fine crystalline particles. The last layer was formed mainly of (Ni,Cu)3Sn4 with some amount of (Cu,Ni)6Sn5 and Ag4Sn phases. The voids observed in the NiP-amorphous layer after processing can be considered as the potential source of the “black pad” failure.

The structure, phase composition, and their thermal evolution were studied in case of ternary Al–Zn–Mg alloys before and after high-pressure torsion (HPT) in Bridgman anvils. The as-cast non-deformed alloys contained the fine particles of Mg32(Al,Zn)49 (τ phase), MgZn2 (η phase), AlMg4Zn11 (η′ phase), and Mg7Zn3 phases embedded in the matrix of Al-based solid solution. During heating in differential scanning calorimeter (DSC), all these phases dissolved around 148 °C. The τ nanoparticles coherent with (Al) matrix-formed instead around 222 °C. HPT of the as-cast alloys strongly refined the grains of (Al) solid solution from 500 μm to 120–150 nm. The particles of τ, η, η′, and Mg7Zn3 phases fully dissolved in the (Al) matrix. During the following DSC-heating, particles of η phase appeared and grew. Their amount became maximal around 166 °C. The growth of η phase in the fine-grained HPT-treated alloys instead of τ phase in the coarse-grained ones is explained by the shift of the (Al) + η/(Al) + η + τ/(Al) + τ lines in the Al–Zn–Mg ternary phase diagram due to the grain boundary (GB) adsorption. At 166 °C the η phase formed the continuous flat layers in numerous (Al)/(Al) GBs. This corresponds to the complete GB wetting by the η phase. Other (Al)/(Al) GBs contain separated lenticular η particles (incomplete GB wetting). Increasing the temperature from 166 to 320 °C led to the disappearance of the completely wetted (Al)/(Al) GBs. In other words, the transition from complete to the incomplete wetting of (Al)/(Al) GBs by the η phase proceeds between 166 °C and 320 °C.

The paper presents the results of the texturization process of the multicrystalline silicon wafers carried out in ternary HF/HNO3/diluent solution, where the diluent was either CH3COOH or H2O, at varying HF/HNO3 volume ratio and different time of texturization process. The technique of scanning electron microscopy was used to characterize the morphology of the obtained multicrystalline silicon surfaces, with subsequent surface reflectivity measurements. The appropriate selection of mixture components lead to a significant reduction in the reflectivity of the incident solar radiation in the relatively short time of 60 seconds. The resultant electric parameters were nearly the same as those for the commercial samples but obtained after 3 minutes.