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The processes of rolling and annealing of explosively welded multi-layered plates significantly affect the functional properties of the composite. In current research, fifteen-layered composite plates were fabricated using a single-shot explosive welding technique. The composites were then rolled up to 72% to reduce layer thickness, followed by annealing at 625 °C for varying times up to 100 h. Microstructure evolution and chemical composition changes were investigated using scanning electron microscopy equipped with energy-dispersive spectroscopy. The mechanical properties of the composite were evaluated by tensile testing, while the strengths of individual layers near the interface were evaluated by micro-hardness measurements. After explosive welding, the wavy interfaces were always formed between the top layers of the composite and the wave parameters decreasing as the bottom layers approach. Due to the rolling process, the thickness of Ti and Al layers decreases, and the waviness of top interfaces disappeared. Simultaneously, the necking and fracture of some Ti layers were observed. During annealing, the thickness of layers with chemical composition corresponding to the Al3Ti phase increased with annealing time. A study of growth kinetic shows that growth is controlled by chemical reaction and diffusion. The results of micro-hardness tests showed that after annealing, a fourfold increase of hardness can be observed in the reaction layers in relation to the Ti, while in relation to Al, the increase of hardness is even 15 times greater.

The interplay of various hardening and softening processes during explosive welding and post-processing annealing have been analysed in titanium/copper bimetallic sheets using scanning electron microscopy and microhardness measurements. Severe plastic deformation and intermetallics’ formation are typical processes leading to hardening, whereas dynamic/static recrystallization and the transformation of amorphous phases into crystalline ones lead to softening. In the as-welded state the interfacial layers of both parent sheets are severely deformed. However, they can undergo intense recrystalization in areas near large melted zones. Inside the melted zones a wide variety of chemical compositions can be detected, however, most of the phases do not appear in the Ti-Cu equilibrium phase diagram. The post-processing annealing at 973 K for 1 h leads to full recrystallization of severely deformed layers of parent sheets and transforms the non-equilibrium phases forming melted zone into the equilibrium TiCu4 and Ti3Cu4 ones via spinodal decomposition. Simultaneously, the growth of four intermetallic layers: Ti2Cu, TiCu, Ti3Cu4, TiCu4 situated along the whole interface was detected.

This paper presents a comprehensive study of the microstructure-property relationships in Ta and stainless or carbon steel composites, fabricated by explosive welding using Cu interlayer. Employing scanning (SEM) and transmission (TEM) electron microscopy and X-ray synchrotron diffraction, a complex microstructure of interfacial layers was examined. Particular attention was placed on the description of the phase transformation mechanisms in the reaction regions, and the competition between the strain-hardening and softening processes in parent sheets. SEM and TEM analyses showed that Cu and Ta nanoparticles, and small dendrites, dominated the reaction regions near the Ta/Cu interfaces, whereas the nano-grained phases having more complex chemical compositions were identified near the Cu/steel interfaces. SEM orientation mapping revealed that the interfacial layers of the parent sheets underwent severe plastic deformation as a result of dislocation slip, twinning, and shear banding. Such heavily deformed areas can easily undergo recovery and recrystallization already during clad processing. In consistence with these findings, the micro-hardness values of the welded sheets increased as the joining interface approached, except for the layers directly adhering to large reaction regions, where a decrease in micro-hardness was observed. However, the solidified melt regions were essentially softer than the strain-hardened layers of both steels. Based on experimental results a new explanation for the reaction region formation was proposed and a significant modification of the description of the interfacial microstructure of parent sheets was done. Finally, the effect of microstructural changes on the clads properties was discussed.

Microstructure evolution in the bonding zones of explosively welded tantalum/stainless steel (304L) and tantalum/copper/stainless steel (304L) clads was examined by scanning electron microscopy (SEM) equipped with electron backscattered diffraction (EBSD) facility. To support the microstructural findings mechanical properties of the interfacial layers were evaluated using microhardness measurements. SEM/EBSD analyses showed that the interfacial layers undergo severe plastic deformation which produces fine equiaxed and/or thin flattened grains. Concurrently, other deformation mechanisms such as twinning, deformation banding and shear banding are developed. It has been established that severely deformed areas can easily undergo recovery and recrystallization already during clad processing. This leads to the formation of new stress-free grains near the interface. During these processes, the strain-hardened structure of flattened grains is replaced by small columnar or equiaxed ones free of dislocations. The microhardness of welded sheets increases significantly as the distance from the joining interface decreases, but aside from the volumes directly adhering to large melted zones, where a drop of microhardness is observed.

The effect of interfacial microstructure on the electro-mechanical properties of explosively welded titanium and copper plates is discussed. Mechanical testing proved that using detonation velocities ranging from 2000 to 3000 m s−1 and stand-off distances from 1.5 to 9.0 mm, joints that satisfy the strength criteria for a good quality clad were produced. Scanning electron microscopy images show that all interfaces exhibit a wave character. It was noticed that as the stand-off distances and detonation velocities increase, the amplitude and period of the waves, as well as the quantity of the melt zones, increase as well. Also, as the interface waviness and volume fraction of the melt zones increase, the resistivity increases substantially. The experimental data demonstrate that the bonding between both metals is always achieved by surface melting of several tenths of a nanometer, which can be detected only by transmission electron microscopy. Most of the phases that form within the melt zones do not appear in the equilibrium phase diagram and show an amorphous/nano-grained structure. Only a very small amount of equilibrium phases such as CuTi3, Cu3Ti, Cu4Ti3 was revealed employing synchrotron X-ray diffraction.

In this work the results of trials aimed at selecting optimal settings of the explosion welding process of 10 mm thick zirconium (Zr 700 grade) plates with carbon steel (P265GH grade) are presented. A bimetal Zr-steel and trimetal Zr-Ti-steel and Zr-Zr-steel where: 2 mm Ti and 3 mm Zr were used as a technological intermediate layer facilitating the bonding. The research was carried out for as-bonded joints, i.e. immediately following explosion welding. Structural analyses in leyers near the interface were focused on the characteristic of the joint interface. Mechanical properties of the obtained clads were measured with shearing, peel and lateral bending tests. Systematic measurements of microhardness distribution enabled analyzing the strain-hardening of the material resulting from explosion welding both at the bond interface zone and throughout the whole section of the clad. It was established that during explosion welding with 10 mm Zr 700 the application of the 2 mm or 3 mm thick interlayers of Zr70 or Ti grade 1, respectively, allows obtaining a joint with good mechanical properties and optimal characteristic of the interface.

The microstructure of the interfacial layers of explosively welded Ta/stainless steel (SS) and Ta/Cu/SS composites is investigated by X-ray synchrotron radiation, scanning (SEM), and transmission (TEM) electron microscopies. SEM analyses show that all interfaces between joined sheets undergo wave-shaped deformation with the solidified melt regions situated preferentially in the wave vortexes and at the wave crests. These reaction regions show a nonuniform distribution of phases in terms of chemical composition with elements belonging to both neighboring sheets. According to TEM analyses and synchrotron X-ray measurements, the solidified melt regions between Ta and SS predominantly consist of brittle, amorphous, or nanocrystalline phases that are not observed in equilibrium phase diagrams. The microstructure of the solidified melt near the Ta/Cu interface is dominated by Cu and Ta nanoparticles and small dendrites, typically less than 100 nm in diameter, whereas nanosized crystalline phases with complex chemical compositions are identified near the Cu/SS interface.

This study aimed to analyze the effect of the impact velocity of a Zr 700 flyer plate explosively welded to a Ti Gr. 1/P265GH bimetallic composite on the residual stress formation, structural properties, and tensile strength. The residual stresses were determined by the orbital hole-drilling strain-gauge method in a surface layer of Zr 700 in as-received and as-welded conditions. The analysis of the tensile test results based on a force parallel to interfaces was used to propose a model for predicting the yield force of composite plates. Compressive residual stresses found in the initial state of the Zr 700 plate were transformed to tensile stresses on the surface layer of the welded Zr 700 plate. A higher impact velocity resulted in higher tensile stresses in the Zr 700 surface layer. To increase the resistance of the composite plate to stress-based corrosion cracking, a lower value of impact velocity is recommended in the welding process.

In this work, the effects of pretwins on the flow behavior, microstructure, and texture evolution of a rolled AZ31 magnesium alloy during hot deformation along three different orthogonal directions were studied via compression tests conducted at 25–350 °C. The flow behavior along different directions was discussed based on the operation of different deformation mechanisms in twinned and untwinned regions. Detwinning was the dominant deformation mechanism during compression in the normal direction at low temperatures, but ceased as the temperature increased to 250 °C. In the latter condition, the effect of pretwins on the texture reorientation led to a decrease in the yield strength. Pretwins stimulate the microstructure condition preceding dynamic recrystallization (DRX) during the compression of samples along the rolling and transverse directions, leading to lower peak strains. The results showed that the pretwins increased the grain size and fraction of DRX at 250 °C. The greatest increase in the DRX fraction was obtained for deformation parallel to the normal direction. The effect of pretwins on the grain boundary characteristics of the samples deformed along the normal direction was investigated. The pretwinned samples showed more significant texture rotation for dynamically recrystallized grains compared with parent grains during deformation parallel to the normal direction.

International audience; The free surface effect on the grain crystallography and morphology during recrystallization has been studied in stable Goss {110} and brass {110} - oriented single crystals of Al-1%wt.Mn alloy. The samples were plane strain compressed up to a strain of about 0.5 to develop a homogeneous structure comprising two sets of symmetrical microbands and then lightly annealed. The variation of recrystallization after annealing was then analysed by optical microscopy and SEM/EBSD on different cross-sections. The results are discussed in terms of the misorientation angle and axis distributions. The free surface provokes high frequency nucleation leading to a small grain size compared to internal sections of the bulk sample. However, the free surface and surface 'quality' do not modify the orientations of the recrystallized grains, i.e. similar groups of recrystallized grain orientations were observed for all sections. This leads to a strong misorientation relation between deformed/recovered area orientations and the limited number of groups of recrystallized grain orientations, basically the same as those observed during bulk recrystallization of similar crystals.

The crystallographic aspects of nucleation of cube grains during annealing have been analyzed in (234)[20-28 11] - oriented aluminum single crystal. The samples were plane strain compressed in a channel-die up to logarithmic strains of 0.5 (40%) and then annealed to develop initial and final stages of primary recrystallization. The deformed and annealed samples were analyzed using scanning electron microscopy equipped with EBSD facility. Local orientation measurements reveled that significant part of the sample deforms homogeneously with only small deviation from the initial crystal orientation. The heterogeneities were thin bands of localized strain in which the crystal lattice rotate towards another variant of S orientation. After annealing the orientations identified inside deformed/recovered areas were similar to that observed in the sample just after deformation. The crystal lattice of recrystallized grains exhibit a well-defined clockwise and anticlockwise rotations around the axes grouped near all normals of the {111} planes of the deformed/recovered state. The cube grains were observed in both homogeneously and heterogeneously deformed areas despite the cube-oriented nuclei surrounded by high angle boundary were not present in the as-deformed structure.

Microstructure and phase constitution in the bonding zone of tantalum and stainless steel explosively welded clads were examined by transmission (TEM) and scanning electron microscopy as well as synchrotron radiation. The macroscale analyses showed that the interface between joined plates were deformed to a wave-shape with solidified melt inclusions located preferentially at the crest of the wave and in the wave vortexes. The micro- and nanoscale analyses revealed a very thin reaction layer at the flat parts of the joint plates. The microstructure and phase distribution of the solidified melt strongly depend on the localization. The melted zones locked inside the wave vortexes predominantly show a uniform chemical composition, whereas those situated at the wave crest a non-uniform phase distribution. TEM investigations of the solidified melt zones unveiled amorphous and nanocrystalline phases of different chemical composition incorporating elements from the joined plates. The parent plates appear to be affected by explosive welding exhibiting a strong increase of dislocation density near the joint. Close to the thicker pockets of the solidified melt recovery and recrystallization processes were observed. Keywords: Explosive welding, Ta/stainless steel clad, Amorphous and nanograins, SEM, TEM, Synchrotron radiation

Distributions of residual stress components in explosively welded three-layer plate composed of titanium Grade 12, titanium Grade 1 and SA516 Grade 70 steel are investigated in this paper. The study applied the sectioning and the hole-drilling strain gage methods for residual stress measurement. The results have shown an inhomogeneous residual stress distribution, approximated by fourth-order polynomial along the thickness of a three-layer plate. Biaxial compressive residual stress state is observed in titanium Grade 12 and Grade 1 layers which change to tensile type in the vicinity of the interface between titanium Grade 1 and steel. Microstructure observation reveals the presence of the adiabatic shear bands in titanium Grade 12 layer at the interface with titanium Grade 1 interlayer. The observed distribution of residual stress components is justified by the occurrence of the shock wave phenomena.

Microstructure and phase in the bonding zone of explosively welded Ti/Al multilayer clads were examined by optical microscopy, scanning and transmission electron microscopy. The defect-free multilayer composite was successfully formed. The macro-scale observations showed that the interfaces between joined plates presented mixed wavy/flat shape with solidified melt inclusions located preferentially at the crest of each wave and in the wave vortex. It was found that interfaces of wavy character were always formed in layers near the explosive charge, and flattened with the increase of the distance from the top surface. The micro- scale analyses observations revealed a presence of very thin reaction layer at the flat parts of the joint plates and nano-grained structure of melted zones.

The paper presents the test results of the microstructure, mechanical properties and fatigue cracks obtained for zirconium-steel bimetal under cyclic bending. The research was carried out for initial state bonds, i.e. immediately following explosion welding. The results of mechanical and structural investigations of the intermediate layers were presented. Using scanning electron microscopy (SEM) allowed the initial identification of the forming phases. In order to determine changes in the value of strengthening, microhardness tests of both the weld and the joined plates were performed. Specimens of rectangular cross section were fatigue tested. In the tested specimens, the ratio of heights of base and overlaid materials was h 1 : h 2 = 2.5: 1. In the specimens, the fatigue crack growth was parallel to the applied load. The specimens exhibit the uniform crack growth at both sides of lateral surfaces. Among composite fractures in the zirconium and steel, transcrystalline cracks are dominating.

The influences of microstructure and texture on the early stages of recrystallization of a commercial AA1050 alloy have been characterized with particular attention to cube grain formation. Samples were deformed along two deformation modes to form different as-deformed texture components and then lightly annealed: one group was plane strain compressed (PSC) in a channel-die, whereas the second group was deformed by equal channel angular extrusion (ECAE). The textures were measured by X-ray diffraction and SEM/EBSD. After both deformation modes a very weak residual cube texture component was observed in the samples. Cube-oriented grains were not formed during annealing of the ECAE samples whose main as-deformed texture components were close to {124} . During recrystallization these transformed to two components of ∼{100} and ∼{221} -type essentially by rotations. Cube grains were extensively formed only during annealing of PSC samples. They were situated preferentially inside or in between the S-oriented deformed areas with local misorientations about axes.

Shear bands were developed during accumulative back extrusion of Mg-3Al-1Zn alloy at 130 °C. Transmission electron microscopy was employed to study the substructural evolution prior to and during the development of macro shear bands. The results illustrated that nanograins with mean size of 100 nm were formed within the bands. The observations revealed that flow localization in magnesium is preceded by interactions of deformation twins, dislocations and micro shear bands. The substructure within the bands is evolved through development of rectangular subgrains as well as subdivision of elongated grains. These substructures transformed subsequently into equiaxed nano-sized grains through continuous recrystallization. EBSD analysis confirmed the contribution of extension twinning during shear band development.

The predominant crystallographic relations between nuclei and simple deformation structures have been characterized in Al and Al-1%wt.Mn alloy single crystals of stable Goss{011}〈001〉 and brass{110}〈112〉 orientations. Samples were deformed in a channel-die to develop a homogeneous structure comprising two sets of symmetrical microbands and then lightly annealed to 10%–20% recrystallization. SEM/EBSD measurements revealed that the misorientation angles across the recrystallization interfaces are grouped in the range 25–55° (with a maximum at 35–45°) around axes located near, but rarely at, the normals of {111} planes. These misorientations are much higher than those of the as-deformed state. There is also a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations, some of which exhibited growth anisotropy along {111} planes. The results are discussed in terms the creation of twist (low mobility) or tilt (high mobility) grain boundaries of high misorientation by thermally activated, co-ordinated movement of dislocations during recovery. The grain boundaries along which the privileged growth occurs are classified as twist-type since the normal to the boundary plane coincides with the misorientation rotation axis.

This paper assesses the effect of various values of detonation velocity on the quality of the bond zone. The results of structural, static and fatigue studies were presented for bonds in the initial state. Depending on the applied technological settings of welding, most cases displayed a wavy bond with highly diversified parameters of the wave. High detonation velocities favoured the formation of waves with great height and length and clearly affect the increase in the volume of hard and brittle regions of melt in the bond zone. Increased volume of the melted regions in the bond zone results in the decrease of fatigue resistance and strength properties of the clads.

The crystallographic aspects of recrystallization twinning have been characterized in {110} and {110}-oriented single crystals of Cu-2%wt.Al and Al-1%wt.Mn alloys. The samples were plane strain compressed to logarithmic strain of 0.52 and then lightly annealed. SEM/EBSD local orientation measurements on partly recrystallized samples demonstrate the appearance of a specific number of new orientation groups of recrystallized grains, which resulted from rotation of the deformed crystal orientations around axes lying near (but rarely at) selected the directions. Then the primary nucleus can transform through the formation of a first generation recrystallization twin. The most frequent situation was that the twinning plane normal was situated near the rotation axis, around which the crystal lattice of the ‘primary nuclei’ rotates. Based on new algorithm to identify coherent and incoherent twin boundaries the influence of free surface on the intensity of annealing twinning was analyzed.

The microstructure and texture evolution in commercially pure aluminium (AA1050 alloy) and copper have been characterized after change in strain path to elucidate the mechanisms of shear bands (SBs) formation and propagation across grain boundaries. Samples were pre-deformed in equal channel angular pressing (ECAP) and further compressed in a channel-die to form two sets of macro-SBs. The deformation-induced sub-structures and local changes in crystallographic orientations were characterized by scanning electron microscopy equipped with a high-resolution electron backscattered diffraction facility. It was found that the mechanism of micro-/macro-SBs formation is strictly crystallographic. In all the grains of the sheared zone a strong tendency to strain-induced re-orientation could be observed. Their crystal lattice rotated in such a way that one of the {111} slip planes became nearly parallel to the shear plane and the (or ) direction became parallel to the direction of maximum shear. This crystal lattice rotation led to the formation of specific SBs components which facilitates slip propagation across grain boundaries without any visible variation in the slip direction.

In this study, unalloyed titanium (Gr.1) and deoxidized high phosphorus copper plates were joined through explosive welding process. Different stand-off distances were used to investigate their influence on the microstructure and mechanical properties of the clad fabricated at the same amount of explosive charge. Microstructures near-the-interface were examined with the use of scanning electron microscope equipped with energy dispersive X-ray spectrometer and then microhardness measurements were carried out on the clad. Microstructure examinations showed that with increasing stand-off distance the length and amplitude of the waviness and the quantity of melted zones in areas near-the-interface increase. The inclusions of the melted zones are formed behind the wave crests on titanium side or within the wave vortex. Microhardness measurements indicate a significant increase of both plates microhardness, especially near-the-interface.

An AZ31magneium alloy was processed through accumulative back extrusion (ABE) process at 280 °C up to six passes. Compressive deformation behavior of the processed materials was studied by employing uniaxial compression tests at room temperature. The results indicated that grains of 80 nm to 1 µm size were formed during accumulative back extrusion, where the mean grain size of the experimental material was reduced by applying successive ABE passes. A deformation texture characterizing with the basal plane mainly lie inclined to the deformation axis was developed. Compressive yield and maximum compressive strengths were measured to increase by applying successive extrusion passes, while the strain-to-fracture dropped. The evolution of mechanical properties was explained relying on the grain refinement effect as well as texture change. It was described that the share of different deformation mechanisms and developing of shearing regions near the grain boundaries may influence the deformation behavior of the ultrafine/nano grained AZ31 alloy.

The recrystallization grain orientations developed during annealing of a deformed single crystal have been characterized by in-situ TEM and ex-situ SEM. Single crystal samples of Al–1 wt.%Mn alloy of brass(110) [1-1-2] orientation were deformed in a channel-die to develop 2 sets of intersecting microbands at strains of 0.51 and 0.92 and then lightly annealed. Local orientation measurements demonstrate a strong relation between the deformed orientations and the limited number of recrystallized grain orientation groups. The misorientation angles across the recrystallization front were grouped in the range 25–55° (with a maximum near 40–45°) around axes located near three normals of the 4 {111} planes; the [1-11] rotation axis parallel to the transverse direction was not found. Two groups of rotation axes were identified: (i) rotation axes very close to the or directions, and (ii) a scattered sequence between – , – or – directions. The orientations of new grains that nucleate during thin foil heating in TEM were compared with those formed during static recrystallization of bulk samples analysed by SEM/EBSD, both in the centre section of electropolished samples and in near-surface areas of abraded samples. In all experiments the new grain orientations belong to the same groups and the distribution of misorientation axes across the recrystallization front was similar.

The occurrence of continuous dynamic recrystallization in a solutionized WE43 alloy during compressive deformation at 450 °C was studied. It was revealed that dynamic formation of β ' second phase particles may exhaust strain-hardening capacity of material, causing the deformation to be concentrated in shear regions. The results showed that prismatic systems play the role as dominant deformation mechanism during shear band formation. The promotion of dislocation activity in this regions assist in the development of low angle boundaries, the misorientation of which is gradually increased with further deformation. The results indicated that, unlike common magnesium alloys, continuous dynamic recrystallization in the RE-containing experimental alloy involves the rotation of grains about non-basal poles. This was discussed relying on the pronounced contribution of non-basal slip during recrystallization of grains within shear regions.

In this work, the competition between various hardening and softening processes in explosively welded (EXW) and post-annealed Ti/Cu composites was studied using scanning and transmission electron microscopy, mechanical testing and numerical modelling. The mesh-free numerical model appropriately reproduces the formation of a wave-like morphology, including vortices, and provides useful insights into the actual temperature, plastic deformation, stress, and pressure fields in layers near the welding interface. During clad formation, heat transfer between the large melted zones and severely deformed layers of the parent sheets induces recrystallisation which leads to softening. Near the interface, this process leads to the transformation of flattened grains into equiaxed, fully recrystallised ones. The most important phase transformations upon EXW occur because of local melting and high-speed cooling. This melting and cooling lead to the formation of ultra-fine-grained, pure Ti, and amorphous intermetallic phases with high hardness. Upon further annealing at 700 °C, full recrystallisation of deformed structures is observed for a short annealing time of 0.25 h. Simultaneously, the transfer of atoms across the interface leads to the formation of four sublayers composed of equilibrium intermetallic phases: Ti2Cu, TiCu, Ti3Cu4, and TiCu4. All these phases are distributed along the entire length of the welding interface. Although the zones of solidified melt and new intermetallic layers exhibit higher hardness than the parent sheets, the recrystallised structure near the interface leads to a decrease in the overall clad strength.

The influence of post-process annealing on the growth kinetics of the intermetallic phases and mechanical properties of titanium/copper bimetallic sheets were analysed using scanning and transmission electron microscopies, X-ray synchrotron radiation, and mechanical testing. In order to weld two metal sheets, an explosive welding technique was utilised. Subsequently, the clads were subjected to post-weld annealing at 973 K from 0.25 to 1000 h. In the bonded state, the interface exhibited a wavy structure with only a small amount of solidified melt zones, composed of non-equilibrium phases of variable chemical compositions. After short annealing times ( 1 h), the growth of four intermetallic layers: Ti2Cu, TiCu, Ti3Cu4, and TiCu4 situated along the entire interface is predominant. It was observed that the phases enriched with Cu and Ti were situated near the Cu and Ti parent sheets, respectively. The nano-hardness of the intermetallic phases decreased as the Ti content increased, whereas the Young's modulus reached its highest values for phases with equiatomic or close-to-equiatomic composition.

In this study, the effect of post-processing heat treatment on the interface morphology and kinetics of intermetallic phase growth in titanium/copper bimetallic sheets were analyzed using a scanning electron microscopy and mechanical testing. Ti/Cu composite was fabricated by explosive welding. Then, clads were subjected to the post-welded annealing at 973 K for times ranging between 15 min and 100h. In the as-bonded state, the interface shows a wavy character with a limited number of melted zones, which are mostly composed of phases that are not observed in the Ti-Cu equilibrium phase diagram. Short-term annealing is shown to transform non-equilibrium phases into equilibrium ones, such as TiCu4 and Ti3Cu4. For longer annealing times, the growth of four intermetallic sublayers (Ti2Cu, TiCu, Ti3Cu4, and TiCu4) distributed along the entire interface is detected. However, the growth kinetics of particular sublayers was different. Volume fraction estimation of intermetallic phases at annealing times under study revealed the largest thickness for TiCu and TiCu4 phases. The nano-hardness of intermetallic sublayers was found to drop with the Ti content.

The paper describes the structure, mechanical properties and fatigue cracks growth in explosively welded zirconium – carbon steel cladding system subjected to long-lasting temperature impact. After annealing at 600 °C for 10 and 100 hours the samples were subjected to microscopic observations and finally the microhardness, tensile strength and cyclic bending were determined. In the deformed specimens the initiation of fatigue cracks occurred in the steel whereas further cracks growth occurred parallel to the applied load. in polish Wpływ długotrwałej obróbki cieplnej na trwałość zmęczeniową bimetalu cyrkon-stal W pracy opisano strukturę, właściwości mechaniczne oraz rozwój pęknięć zmęczeniowych w układach platerów cyrkon-stal zgrzewanych wybuchowo, poddanych długotrwałemu oddziaływaniu temperatury. Próbki w stanie po spojeniu wygrzewano w temperaturze 600 °C w czasie 10 i 100 godzin, a następnie poddano obserwacjom mikroskopowym, określono twardość, wytrzymałość na rozciąganie oraz poddano wahadłowemu zginaniu. W odkształconych próbkach zaobserwowano wzrost pęknięć zmęczeniowych równolegle do przyłożonego obciążenia, przy czym inicjacja pęknięć występowała w stali.

Microstructure and phase in the bonding zone of explosively welded Ti/Al multilayer clads were examined by optical microscopy and scanning electron microscopy. The defect-free multilayer composite was successfully formed. The macro-scale observations showed that the interfaces between joined plates presented mixed wavy/flat shape with solidified melt inclusions located preferentially at the crest of each wave and in the wave vortex. It was found that interfaces of wavy character were always formed in layers near the explosive charge and flattened with the increase of the distance from the top surface. The micro-scale analyses observations revealed a presence of very thin reaction layer at the flat parts of the joint plates and nano-grained struc- ture of melted zones. in polish Mikrostruktura i właściwości mechaniczne wielowarstwowych platerów na bazie Al i Ti wytwarzanych z wykorzystaniem energii wybuchu W pracy analizowano zmiany mikrostrukturalne oraz formowanie się nowych faz w wielowarstwowych układach platerów zbudowanych na bazie Ti i Al. Wykorzystano techniki mikroskopii optycznej i skaningowej mikroskopii elektronowej, pomiary mikrotwardości, a także próbę zginania w warunkach udarowych. Obserwacje w skali makro pokazały, że w procesie spajania wytworzono 15-warstwowy plater wolny od nieciągłości strukturalnych. Powierzchnie połączenia uległy silnemu odkształceniu i wykazywały mieszany falisto-płaski charakter ze strefami przetopień preferencyjnie lokowanymi na grzbiecie oraz w zawinięciach fal. Zaobserwowano, że silnie pofalowane granice połączenia zawsze formowały się w warstwach położonych w pobliżu ładunku wybuchowego. Analizy w mikro skali udokumentowały występowanie cienkiej warstwy przetopionej o silnie rozdrobnionej strukturze.

The microstructure and microtexture evolutions during shear banding of very fine grained commercially pure aluminium (AA1050) have been characterized to elucidate the mechanisms of band formation and propagation across layered microstructures and the resulting texture evolution. Samples were pre-deformed in ECAP to 6 passes via route C, then machined and further compressed in a channel-die to form two sets of copper-type macroscopic shear bands (MSBs). The local changes in microstructure and crystallographic orientations were characterized by SEM equipped with a high-resolution EBSD facility. The ECAP-processing led to the formation of a fine-grained structure composed of complementarily oriented layers parallel to the transverse direction and inclined ~20° to the extension direction (ED). During the secondary straining in the channel-die, the layers exhibited two rotation tendencies: (i) a global rotation of the layers towards the compression plane, and (ii) a deflection of layers within narrow areas. The latter increased the layers’ inclination with respect to ED and led to kink-type bands, which are the precursors of MSBs. The mechanism of MSB formation is strictly crystallographic since in all the grains of the sheared zone, the crystal lattice rotated such that one of the {111} slip planes became nearly parallel to the shear plane and the 〈011〉 direction became parallel to the direction of maximum shear. This strain-induced crystal lattice rotation led to the formation of specific MSB components that facilitated slip propagation across the grain boundaries.

The microstructure of an explosive cladding joint formed between parallel Zr700 alloy and carbon steel plates was examined with the use of scanning and transmission electron microscopes equipped with energy dispersive spectrometry. The study focused on near-the-interface microstructural changes and possible interdiffusion between the plates. At the macro-scale, the interfaces were outlined by a characteristic sharp transition, indicating that there was no mechanical mixing between the welded metals in the solid state. At the micro-scale, the melted zones often showed non-uniform swirl-like areas of a similar contrast. The nano-scale analysis revealed that the melted areas were composed of mixed amorphous and nano-crystalline phases. The bonding was always achieved by way of surface melting of the joined materials, which might be invisible for observation methods other than transmission electron microscopy.

Early stages of recrystallization were observed for the Al-Mn-Mg-Zr(Sc) aluminium alloy containing a fine second phase particles. The samples were plane strain compressed to 40%, 60% and 83% and then annealed. The processes of the recovery and the nucleation of new grains were analysed with the use of scanning electron microscopy equipped with a high resolution electron backscattered diffraction facility. The deformed alloy contained a structure of flat grains situated parallel to the compression plane. After annealing, the structure coarsened. However, the growth of the new grains was strongly hindered by the presence of particles, and the elongated shape of the deformed grains was conserved up to the later stages of recrystallization. In the case ofthe samples deformed up to 40%, the structure was transformed by the mechanism of continuous recrystallization, whereas, in the case of the samples deformed up to 60% or 83%, both mechanisms- of continuous and discontinuous recrystallization - were valid. A particular role in the rise of thenuclei and the structure spheroidization is attributed to the thermally activated migration of the low-angle grain boundaries and the movement of the dislocations stored inside the cells. This leads to an increase of the misorientation angles across the pre-existing low-angle boundaries.

The effect of annealing on the microstructure and the texture development was investigated in a particle containing AA3104 aluminium alloy. The samples were processed at room temperature by high-pressure torsion (HPT) up to ten turns. The nucleation of new grains was analyzed by a transmission electron microscope equipped with a system for local orientation measurements and a heating holder.The shear deformation induces a decrease of the grain size. After the first two turns of the HPT processing the initial structure of large grains was ‘transformed’ into a structure of fine cells/grains with the diameter of a few tens of nanometers. In the central areas of the samples the elongated shape of the cells/grains was observed up to six turns. For higher deformations, this structural inhomogeneity was totally removed and only the equiaxed grains were observed. The crystal lattice of small grains rotates in such a way that the direction is parallel to the compression axis. After annealing the structure coarsened. Nevertheless, after primary recrystallization, the structure was still composed of relatively fine and equiaxed grains of a similar size. In most of the observed cases the size of the recrystallized grains in the areas close to and far from the large second phase particles was similar. The recrystallization leads to the creation of new texture components. The new grain orientations lost the positions typically observed in the deformed state and showed the tendency for the coincidence of the crystallographic directions with the compression axis.

The layers near the interface of explosively welded plates were investigated by means of microscopic observations with the use of transmission electron microscopy (TEM) equipped with energy dispersive spectrometry and scanning electron microscopy equipped with electron backscattered diffraction facility (SEM/EBSD). The metal compositions based on carbon or stainless steels (base plate) and Ti, Zr and Ta (flyer plate) were analyzed. The study was focused on the possible interdiffusion across the interface and the changes in the dislocation structure of bonded plates in the layers near-the-interface.It was found that the extremely rapid temperature increase followed by high cooling rates in the areas near the interface favour the formation of metastable phases. The crystalline or glassy nature of the phases formed inside melted zones strongly depends on the chemical composition of bonded metals. The amorphous phases dominates the melted zone of the (carbon or stainless steel)/Zr whereas the mixture of amorphous phases and nano- grains were identified in (carbon steel)/Ti and (stainless steel)/Ta clads. The elongated shape of the (sub)grains and the randomly distributed dislocations inside them as well as the shear bands and twins observed in the layers near-the-interface of all investigated clads, clearly indicated that during explosive welding, the deformation processes were prevailing over the softening ones.

This paper assesses the effect of various values of detonation velocity on the quality of the bond zone, and thus the properties of bimetal zirconium (Zr 700) - steel (P355NL). The research was carried out for as-bonded welds, i.e. immediately following explosion welding. The results of shearing, peeling and tensile tests as well as macro-scale structural analyses were presented. In order to determine the changes in the value of strain hardening, the microhardness measurements across the interface were carried out. Based on the performed analyses it can be claimed that, depending on the applied technological settings of welding, most cases displayed wavy bond with highly diversified parameters of the wave. The changes observed with the detonation velocity are non-monotonic. High detonation velocities favored the formation of waves with large height and length and strongly affect the increase of the volume of brittle melted zones. Increased volume of the melted regions results in strong decrease of strength properties of the clad. The analysis of strength test results allows claiming that a small volume of melted regions in the bond considerably improves the strength of the bond.As a result of explosion welding, strain hardening of the joined materials occurs near the interface. In the case of clad fabricated using high technological parameters the increase of strengthening and the depth of its influence in the interface area is observed.

The objective of this paper is to identify the predominant crystallographic relations between deformed state and recrystallized grains during the early stages of recrystallization of fcc metals with medium and low stacking fault energy. The experimental investigations, based on SEM/EBSD measurements, have focused on the transformations which occur in plane strain compressed single crystals with stable orientations. After annealing the disorientation across the recrystallization front 'defines' the final rotation by angles in the ranges of 25-35o and 45-55o around axes mostly grouped near the , , and directions located around the normals of all four {111} slip planes.

The layers near the interface of explosively welded plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (and Focus Ion Beam technique for the thin foils preparation) equipped with energy dispersive spectrometry. The metal compositions based on steels and Ti, Zr, Ta or Cu, were analyzed. The study was focused on the identification of the intermetallic phases inside the melted zones, the possible interdiffusion between the bonded metals and the changes in the dislocation structure.

A wrought AZ31 magnesium alloy was severely deformed through a novel continuous severe plastic deformation technique, called accumulative back extrusion. The microstructure and texture obtained after applying multiple deformation passes at a temperature range of 80–380 °C were characterized. After a single pass at 80 °C an ultrafine/nano grained microstructure was obtained, while the initial texture was completely replaced by a new fiber basal texture, 40° inclined to transverse direction. As the processing temperature increased, the obtained texture intensities were strengthened, though the c-axis of crystals gradually rotated towards transverse direction and a fiber texture parallel to normal direction was developed. Moreover, repetitive accumulative back extrusion was associated with tendency of basal plane to lie parallel to transverse direction, while the orientation of prismatic planes showed a random distribution around normal direction. After eight passes the most noticeable texture included fiber basal texture oriented almost parallel to the transverse direction, and perpendicular to the extrusion direction and parallel to the normal direction. The maximum texture intensity was decreased as the number of passes increased, which is attributed to strain path change involved during each consecutive accumulative back extrusion pass as well as promoted contribution of non-basal slip systems.