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This work presents the influence of microstructural constituents on liquation crack formation in the cast Ni-based superalloy, René 108. The investigation was divided into three parts: characterisation of the material's microstructure in pre-weld condition, hot ductility studies and analysis of liquation cracking induced by the gas tungsten arc welding process. Using advanced electron microscopy techniques it is shown that the base material in pre-weld condition is characterised by a complex microstructure. The phases identified in René 108 include γ matrix, γ' precipitates, MC and M23C6 carbides, and M5B3 borides. Based on Gleeble testing, it was found that René 108 is characterised by high strength at elevated temperatures with a maximum of 1107 MPa at 975 °C. As a result of constitutional liquation, the superalloy’s strength and ductility were significantly reduced. The nil strength temperature was equal to 1292 °C, while the nil ductility temperature was 1225 °C. The low ductility recovery rate (32.1), ratio of ductility recovery (36.2) and hot cracking factor (Rf = 0.05) values confirmed the low weldability of Renѐ 108. In the heat-affected zone (HAZ) induced by welding, constitutional liquation of mainly γ' precipitates, with a contribution of M23C6 carbides and M5B3 borides, was observed. The thin non-equilibrium liquid film, which formed along high-angle grain boundaries, led to crack initiation and their further propagation during cooling. The eutectic γ–γ' re-solidification products are visible on the crack edges.

The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ/γ′ interface is strongly enriched in Co and Cr and depleted in Al.

The effect of yttrium additions on the glass formation of the Zr50Cu40Al10 alloy with high oxygen content was investigated. Unlike other reports showing the positive effect of alloying Zr-based alloys with a few percent of rare earth elements, we examined the Y-to-oxygen ratios. As calculated, a stoichiometric amount of yttrium (2808 at ppm) is required to bind all the oxygen (4212 at ppm) to form the Y2O3. Additionally, the influence of half (1404 at ppm) and double stoichiometric (5616 at ppm) levels of yttrium, with respect to the measured oxygen content to be bound was evaluated. The Y-doped alloys were synthesized by arc melting, followed by suction casting into copper molds with conical and rod cavities. The critical diameter of the undoped alloy was below 3 mm, while stoichiometric and double stoichiometric yttrium concentrations allowed to obtain 5 and 7 mm diameter glassy samples, respectively. Microstructure observations confirmed the scavenging effect of yttrium, leading to the formation of a cubic ( $$ Ia\bar{3} $$ I a 3 ¯ space group) yttrium sesquioxide. The glass forming ability of the alloys was additionally determined based on differential thermal analysis, allowing to propose the best indicator for the studied Zr-Cu-Al alloys.

There is a problem in obtaining a suitable impact strength of the padding weld after cladding with a martensitic filler metal. Too low annealing temperature below 580°C and the excessive annealing temperature above 650°C do not provide adequate impact strength of the padding weld. A heat treatment technology for mixed joints has been developed based on the results of the microscopic observations, X-ray diffraction measurements and transmission electron microscope examination. The problem was identified and a special technology of heat treatment for the dissimilar joint was elaborated. This technology provides a high impact resistance of the padding weld and an appropriate properties of the base material.

The paper presents the results of the investigation of microstructure of the welded X5CrNiCuNb16-4 (17-4PH) steel after solution treatment and aging at 620°C for different periods. The microstructure and the phase composition of the steel was investigated using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM) and the X-ray diffraction (XRD). Hardness was measured for samples aged at different times. Density distributions of Cu precipitates were established. The investigation has shown that the microstructure of the X5CrNiCuNb16-4 steel welds after aging at 620 ° C consists of tempered martensite, fine Cu precipitates and austenite. It was observed that the size of the Cu precipitates increases with increasing the aging time, what affects the decrease of hardness. Simultaneously, the quantity of reversed austenite increases with increase of aging time. It was revealed that enrichment of the austenite in Ni, Cu and C affects the increase of Ms, but this factor does not determine the stability of austenite.

The change of γ′ phase morphology in quenched Ni-based superalloy strengthened by γ′ precipitates was investigated by means of scanning electron microscopy and X-ray diffraction. Lattice parameters of γ and γ′ phases and subsequently the δ parameter were calculated. Relatively high content of gamma prime formers resulted in a substantially high volume fraction of precipitates in the dendrite cores. The volume fraction of γ′ phase was significantly decreased due to dissolution of precipitates in the surrounding matrix, as a result of short-term subsolidus exposure. The lattice parameter of γ′ phase was higher than that of γ phase, which results in a positive δ parameter in fully heat treated (FHT) and also FHT+ Quench conditions. For (200) and (220) reflections the γ/γ′ misfit was lower in the FHT + Q sample.

Quaternary powder mixtures yNi–20Cr–1.5Al–xTiCp (y = 78.5, 73.5, 68.5; x = 0, 5, 10) were deposited on ferritic 10CrMo9–10 steel to form on plates ex-situ composite coatings with austenitic-based matrix. Plasma deposition was carried out with various parameters to obtain eight variants. The microstructure, chemical composition, phase constitution, phase transformation temperatures, and microhardness of the two reference TiCp-free coatings and six ex-situ composites were investigated by X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, thermodynamic simulation, and Vickers microhardness measurements. All composites had an austenite matrix with lattice parameter a = 3.5891–3.6062 Å, calculated according to the Nelson–Riley extrapolation. Microstructural observations revealed irregular distribution of TiCp in the composites. Large particles generally occurred near the external surface due to the acting buoyancy effect, whereas in the interior smaller particles, with an equivalent radius around 0.2–0.6 μm, were present. Due to initial differences in the chemical composition of powder mixtures and also subsequent intensive mixing with the low-alloy steel in the liquid pool, the matrix of the composites was characterized by various chemical compositions with a dominating iron concentration. Interaction of TiCp with matrix during deposition led to the formation of nano-precipitates of M23C6 carbides at the interfaces. Based on the ThermoCalc simulation, the highest solidus and liquidus temperatures of the matrix were calculated to be for the composite fabricated by deposition of 73.5Ni–20Cr–1.5Al–5TiCp powder mixture at I = 130 A. The mean microhardness of the TiCp-free coatings was in the range 138–146 μHV0.1, whereas composites had hardnesses at least 50% higher, depending on the initial content of TiCp.

The microstructure of a Ren&eacute, 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 &deg, C-2h) and aged (900 &deg, C-8h). The &gamma, matrix is mainly strengthened by the ordered L12 &gamma, &prime, phase, with the mean &gamma, /&gamma, misfit, &delta, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary &gamma, precipitates. At the interface of the matrix with secondary &gamma, precipitates, nano M5B3 borides are present. In the interdendritic spaces additionally primary &gamma, precipitates, MC and nano M23C6 carbides were detected. The &gamma, precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of &gamma, formers occurs in coarse &gamma, surrounding MC carbides. Borides M5B3 contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate&rsquo, s morphology. The nano M23C6 carbides enriched in Cr have been formed as a consequence of phase transformation MC + &gamma, &rarr, M23C6 + &gamma, during the ageing treatment.

In situ X-ray diffraction and transmission electron microscopy has been used to investigate Ren&eacute, 108 Ni-based superalloy after short-term annealing at high-homologous temperatures. Current work is focused on characterisation of &gamma, ' precipitates, their volume fraction, evolution of the lattice parameter of &gamma, and &gamma, ' phases and misfit parameter of &gamma, ' in the matrix. Material in the initial condition is characterised by a high-volume fraction (over 63%) of &gamma, ' precipitates. Irregular distribution of alloying elements was observed. Matrix channels were strongly enriched in Cr, Co, W and Mo, whereas precipitates contain large amount of Al, Ti, Ta and Hf. Exposure to high-homologous temperatures in the range 1100&ndash, 1250 &deg, C led to the dissolution of the precipitates, which influenced the change of lattice parameter of both &gamma, ' phases. The lattice parameter of the matrix continuously grew during holding at high temperatures, which had a dominant influence on the more negative misfit coefficient.

The effect of oxygen content on the glass forming ability of the Zr50Cu40Al10 alloy is presented. Two different oxygen levels, 194 ± 26 wt. ppm and 918 ± 72 wt. ppm, in the arc melted and suction cast alloys were obtained using Zr metal of different forms and nominal oxygen contents. Critical diameters for glass formation were determined by microstructural observations of cast conical and rod-shaped samples. Their structures were further investigated by X-ray diffraction. The critical diameter of the alloy with the lower oxygen content was 8 mm, while for the higher oxygen content it was below 3 mm. For the latter, the τ3 (Zr51Cu28Al21) crystalline inclusions were observed in the central part of the 3 mm diameter sample. The fully amorphous samples exhibited a large supercooled liquid range and a high reduced glass transition temperature.

The aim of the present study was to characterize the repair weld of serviced (aged) solid-solution Ni-Cr-Fe-Mo alloy: Hastelloy X. The repair welding of a gas turbine part was carried out using Gas Tungsten Arc Welding (GTAW), the same process as for new parts. Light microscopy, scanning electron microscopy, transmission electron microscopy, microhardness measurements were the techniques used to determine the post repair condition of the alloy. Compared to the solution state, an increased amount of M6C carbide was detected, but M23C6 carbides, sigma and mu phases were not. The aged condition corresponds to higher hardness, but without brittle regions that could initiate cracking.

The paper presents the results of research on the X10CrMoVNbN9-1 (T91) steel after long-term service. The material for testing was taken from a pipe section of a boiler superheater coil serviced for around 105,000 h at the temperature of 540 °C, at the pressure of 12.5 MPa. A quantitative analysis including the measurement of mean diameter of subgrains and precipitates as well as the density of dislocations of the examined steel was performed by means of TEM. The microscopic tests of T91 steel were complemented with the results of tests on mechanical properties which included also the short creep tests. After service, the investigated steel was characterized by a retained lath microstructure of tempered martensite with fine subgrain and quite large density of dislocations as well as numerous precipitates. In the microstructure, apart from the particles of M23C6 and MX (VX, NbC, V-wings), the precipitates of Laves phase and single particles of Z phase were revealed. It has been shown that the extent of degradation of the T91 steel microstructure was minor, which resulted from its low temperature of service. Performed tests of mechanical properties showed that these properties fulfilled the minimum requirements for this steel in the as-received condition. A favorable influence of fine precipitates of Laves phase on mechanical properties was observed. Moreover, an insignificant influence of single precipitates of Z phase on the creep resistance of the examined steel was stated.

Fe–23wt.%Mn–3wt.%Si–3wt.%Al alloy was cast, homogenized at 1150ºC, hot-rolled at temperatures between 1200ºC and 900ºC and next cold-rolled from 5% up to 40% reductions in thickness. Microstructure and texture of this alloy, which has a low stacking fault energy, were defined after cold-rolling. Investigation of transmission electron microscopy and X-ray diffraction showed that mechanical twinning and martensitic transformations (γfcc→εhcp and γfcc→εhcp→α′bcc) took place during cold-rolling. The crystallographic Shoji-Nishiyama (S-N) {00.2}ε║{111}γ, ε ║ γ and Kurdjumov-Sachs (K-S) {111}γ║{101}α’, γ║α’ relations between martensite (ε, α’) and austenite (γ), were found in the coldrolled material.

The present research is part of a project concerning texture and microstructure evolution upon deformation and annealing in a series of various duplex stainless steels. This article shows a comparison of deformation behavior in two grades of duplex steels subjected to cold-rolling over a wide range of reductions. Both steels under examination showed clear differences in chemical composition and their preliminary treatment included different processes of hot plastic working. Optical microscopy was used to examine changes in morphology and formation of a ferrite–austenite band-like structure upon cold-rolling. Transmission electron microscopy was applied to analyze microstructural evolution and deformation behavior within the ferrite and austenite bands. Additional research included texture measurements for both component phases. Special attention was paid to the ferrite–austenite co-deformation and the structural effects resulting from strain localization at high rolling reductions.

7CrMoVTiB10-10 (T24) steel is recommended for fabrication of boiler components such as water walls, water panels or headers without post weld heat treatment (PWHT). The chemical composition of this steel and cooling conditions after welding influence the susceptibility to cracking in weld metal during and after welding. TEM investigations showed that in the as-welded microstructure mixtures of bainite and martensite were dominating. This has an important implication for technological properties.

The paper presents the results of research on the microstructure of high-chromium martensitic GX12CrMoVNbN9-1 (GP91) cast steel after the isothermal ageing process and fatigue process. The fatigue process was performed at room temperature and elevated temperature (600 °C), with the value of total strain amplitude ɛ ac amounting to 0.25% and 0.60%. Microstructural tests of GP91 cast steel were carried out by means of high-resolution transmission electron microscope. Quantitative study performed by means of TEM included the characteristics of changes in the dislocation substructure and morphology of M 23 C 6 carbides. Performed research has shown that the microstructure of the examined cast steel after ageing is characterized by partly remaining lath microstructure with numerous precipitations of the MX and M 23 C 6 type, as well as the Laves phase. It has been shown that the fatigue test at room temperature contributes to the process of dislocation strengthening of the examined cast steel. The increase of fatigue test temperature influences the degree of increase in the matrix softening. The degree of softening of the cast steel microstructure at elevated temperature depends also on the value of strain amplitude e ac . The softening process of the examined cast steel was connected with the decrease of dislocation density and increase of subgrains.

The 17Cr–9Ni–3Mo precipitation hardened (PH) steel was processed after re-melting using different cooling rates including copper plate chilling and the melt-spinning. The effect of different cooling rates and the sub-zero treatment on the microstructure of the 17Cr–9Ni–3Mo steel was studied. The microstructure and the phase composition of the steel was investigated using light microscopy (LM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), the X-ray diffraction (XRD) and Mossbauer spectroscopy. The results show that the microstructure of 17Cr–9Ni–3Mo steel after rapid solidification consists of austenite and δ-ferrite. The quantity of austenite increases with the increase of cooling rate. Sub-zero treatment of the samples cooled at the rate of 4 × 104 K/s and 2 × 105 K/s reduces the quantity of austenite as a result of austenite → martensite transformation. For the samples cooled at the rate of 2 × 106 K/s the quantity of austenite in the microstructure does not change when compared to the state before and after sub-zero treatment. The model for the formation of microstructures during rapid cooling was proposed.

Microstructural changes in the age-hardenable Fe-28wt.%Mn-9wt.%Al-1wt.%C steel during ageing at 550°C for various times have been investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The steel was produced in an induction furnace and the ingot, after homogenization at 1150°C for 3 hours under a protective argon atmosphere, was hot-rolled and subsequently cold-rolled up to 23% reduction. The sheet was then aged at 550°C for various times in an argon atmosphere and cooled in air. XRD analysis and TEM observations revealed a modulated structure and superlattice reflections produced by spinodal decomposition, which occurred during ageing at 550°C. Theexistence of satellites suggests that either (Fe, Mn)3AlCx carbides were formed within the austenite matrix by spinodal decomposition during cooling or chemical fluctuactions occurred between the (Fe, Mn)3AlCx carbides and the austenitic matrix.

The paper presents the results of microstructure of welded joints of hot-dip zinc galvanized steels E275D+Z and stainless steels X5CrNi18-10 (AISI 304, 1.4301) examination. Obtained results show the zinc evaporation from structural steel surface, it deposition on the stainless steel and penetration of it microstructure. The process mechanism is described and illustrated.

The research was carried out on 26Mn-3Si-3Al steel having a low value of SFE. After casting, steel was forged and hot-rolled at the temperatures within the range of from 1200°C to 900. Next, the steel was cold rolled until the deformation of 66% was obtained. Upon the basis of X-ray examination and the observations of microstructures, it was found out that during cold rolling mechanical twinning and the martensitic transformation of austenite in hcp-ε martensite occurred. The crystallographic texture of the γ phase (austenite) and ε phase (martensite) was also examined.

This paper presents structure investigations of the rapidly cooled Fe66Cu6B19Si5Nb4 alloy. A proper selection of chemical composition enabled in-situ formation of the amorphous-crystalline composite during the melt spinning process. Liquid phase separation into the Fe-rich and the Cu-rich phases was confirmed. The microstructures of alloy, melt-spun from 1723 and 1773 K, are composed of the Fe-rich amorphous matrix and Cu-rich spherical crystalline precipitates. For the higher melt-ejection temperature, no coarse precipitates could be observed. Amorphous nature of the Fe-rich matrix was confirmed by presence of a broad diffraction maximum on the X-ray diffraction patterns, a halo ring on the electron diffraction pattern as well as presence of exothermic effects, related to the crystallization of the Fe-rich amorphous matrix, in the differential scanning calorymetry. Beside presence of copper, revealing positive heat of mixing with iron, relatively large supercooled liquid region, was noticed.

The present research is a part of project dealing with structural aspects of ferrite and austenite co-deformation in duplex stainless steels. The examination concerned a development of ferrite and austenite microstructures, major deformation mechanisms operating in both phases and texture formation upon cold-rolling of a model duplex type steel. The investigations showed that the band-like morphology of two-phase structure formed upon processing together with specific starting textures obtained after a preliminary thermo-mechanical treatment exerted significant influence on texture and microstructure development in both constituent phases. Microstructure and texture evolution in examined duplex steel significantly differed from those in one-phase steels. These differences resulted first of all from the role of the phase boundaries acting as the barriers for dislocation movement and affecting the processes of strain localization at higher deformations.

W artykule przedstawiono probe implantacyjną oceny sklonności do pekniec zimnych zlączy spawanych. Przedstawiono rowniez wyniki proby dla stali 7CrMoVTiB10-10 oraz badania w zakresie oceny charakteru przelomu. Evaluation of susceptibility to cold cracking of welded joints in the implant test Abstract The paper presents the implant test method as useful for susceptibility to cold cracking evaluation of welded joints. Moreover, there are presented results of implant test for 7CrMoTiVB10-10 steel and fractures analyses with the use of light microscopy and scanning electron microscopy.

Przedmiotem badań były złącza spawane ze stopu niklu umacnianego roztworowo o nazwie handlowej Hastelloy X. Proces spawania przeprowadzono metodą GTAW (z ang. Gas Tungsten Arc Welding) na materiale w stanie dostawy oraz po eksploatacji tj. pochodzącym z turbiny gazowej. W celu porównania zmian mikrostrukturalnych i własności wykonano badania za pomocą mikroskopii świetlnej, skaningowej oraz pomiary mikrotwardości. Dodatkowo przeprowadzono badania za pomocą transmisyjnej mikroskopii elektronowej (TEM) w obszarze materiału rodzimego po eksploatacji. Wykonane badania TEM były podstawą do stwierdzenia, iż temperatura eksploatacji wpłynęła jedynie na zwiększenie ilości i średnicy wydzieleń węglików typu M6C, natomiast temperatura eksploatacji leżała poza zakresem wydzielania faz wtórnych węglików typu M23C6 i faz topologicznie zwarcie wypełnione σ lub μ. Hastelloy X w stanie przesyconym charakteryzuje się bardzo dobrą spawalności, jednakże może ona ulec obniżeniu w wyniku obecności kruchych i niskotopliwych faz powstałych w trakcie eksploatacji. Microstructure and properties of repair welds with the use of Hastelloy X alloy in the delivery condition and after long term service Abstract The aim of the present study was to characterize repair welds performed on solid solution strengthened nickel-based superalloy also known Hastelloy X. The welding process was performed using GTAW. Process was carried out on materials in solid solution condition (unaged state) and after long term service in gas turbine. In order to compare microstructural changes and properties of welds light microscopy, scanning electron microscopy and microhardness measurements were performed. Additionally, transmission electron microscopy (TEM) of the base material after long term service was carried out. TEM study was the basis for the conclusion that the operating temperature had an impact on increase the amount and diameter of M6C-type carbides. Operating temperature of the turbine part was too low to contribute to the precipitation of M23C6- type carbides and topologically closed packed phases σ and μ. Alloy in solid solution condition has excellent weldability but precipitation of brittle and low melting temperature constituents during service may affect the tendency to cracking.

A new high chromium martensitic steel, VM12, was recently developed for advanced coal-fired ultra-supercritical steam power plants. A very important factor in maintaining high creep resistance during service exposure is its stable microstructure, in particular high dispersion particle strengthening, which slow down the recovery and softening processes of the matrix. Quantitative characterisation of the precipitates in the VM12 steel as received condition and after creep tests up to about 30000 h at 625 °C using TEM was carried out.

The paper presents microstructures and mechanical properties of the melt-spun Fe30Cu32Si13B9Al8Ni6Y2 and Fe44Cu18Si13B9Al8Ni6Y2 alloys. It was found that liquid phase separation of the initially homogeneous melt occurred due to a positive heat of mixing between two major elements. The microstructures of the melt-spun ribbons were composed of the Fe-rich amorphous and the Cu-rich crystalline phases. A significant effect of the melt ejection temperature and the chemical composition (Fe and Cu content) on microstructures of rapidly solidified alloys was revealed. The microstructures of ribbons melt-spun from the miscibility gap region were non-uniform. On the other hand the microstructures of ribbons melt-spun from homogeneous melt temperature region were composed of the spherical precipitates distributed within the matrix. Superior hardness values of the examined ribbons melt-spun from the same temperature were found for the alloy with higher iron content. An increase of the melt-ejection temperature in the homogeneous melt region resulted in hardness decrease in case of the Fe30Cu32Si13B9Al8Ni6Y2 alloy and its increase for the Fe44Cu18Si13B9Al8Ni6Y2 ribbons.

International audience; There are rather few quantitative data on the microstructure of the 9–12%Cr heat resistant steels after long-term creep. This paper presents results of the quantitative measurement of the size of MX precipitates, subgrain size and dislocation density in a P91 steel that had been creep tested for 113,431 h at 600 °C. The same measurements were conducted in the same P91 steel in the as received conditions. Transmission electron microscopy investigations were conducted using thin foils and revealed a decrease in dislocation density and an increase in subgrain size after creep exposure. MX carbonitrides are very stable during thermal and creep exposure of P91 steel at 600 °C up to 113,431 h. Electron backscatter diffraction (EBSD) investigations also revealed a significant change in the substructure of the steel after creep exposure.

The microstructure in the new COST martensitic 12% chromium steel VM12 developed for advanced power stations operated around 625 – 650°C has been investigated in the ‘as-received condition’ and after long-term creep exposure at 625°C up for around 29,000 h. Quantitative TEM analyses of VM12 steel microstructure were undertaken to determine the dislocation density within the sub-grain, the width of the martensite laths/sub-grains and the particle parameters (shape, size, distribution). Phase identification was performed using electron diffraction and X-ray spectrometry.The TEM results showed that thermal exposure and creep deformation at 625°C caused some changes of the VM12 steel microstructure. The statistical quantitative analyses of the microstructural parameters, showed that the sub-grain size and the size of M23C6 precipitates slightly increased after exposure up to 29,000 h. In the creep-tested specimens, microstructural changes were much more pronounced than in the thermally-exposed specime...

The aim of the work was to produce the amorphous/crystalline composite with uniform distribution of fine crystalline soft phase. Silver–copper–titanium Ag 20 Cu 30 Ti 50 alloy was prepared using 99.95 wt% Ag, 99.95 wt% Cu, 99.95 wt% Ti that were arc-melted in argon atmosphere. Then the alloy was melt spun on a copper wheel with linear velocity of 33 m/s. Investigation of the microstructure for both arc-melt massive sample and melt-spun ribbons was performed with use of scanning electron microscope (SEM) with EDS, light microscope (LM) and X-ray diffraction. The thermal stability was evaluated by differential scanning calorimetry (DSC). The properties such as Young modulus and Vickers hardness number before and after crystallization of the amorphous matrix were measured with use of nanoindenter. The microstructure was investigated by transmission electron microscope (TEM). It was found, that the alloy has a tendency for separation within the liquid state due to the miscibility gap which resulted in segregation into Ti–Cu–Ag matrix and Ag-base spherical particles after arc-melting. During rapid cooling through the melt spinning the Ag 20 Cu 30 Ti 50 alloy formed an amorphous/crystalline composite of fcc silver-rich spherical particles within the amorphous Ti–Cu–Ag matrix.

P91 0.10 8.10 0.92 — 0.073 0.18 0.049 — 0.049 0.38 0.38 P92 0.124 9.07 0.46 1.78 0.063 0.19 0.043 0.003 0.043 0.02 0.06 E911 0.105 9.16 1.1 1.00 0.068 0.23 0.039 — 0.072 0.20 0.07 CB6 0.12 10.7 1.4 — 0.05 0.20 0.041 0.008 0.025 0.28 0.10

Transmission electron microscopy (TEM) was used to assess the microstructural changes accompanying semisolid molding of a creep resistant Mg-5%Al-2%Sr alloy. It was revealed that the processing created thixotropic morphologies with globular solids of α-Mg, having well-developed sub-structures. The quickly-solidified liquid fraction, enriched in Al and Sr, led to the formation of increased volumes of a lamellae type Al4Sr phase, surrounding the secondary α-Mg. Traces of Mg17Al12 still existed, predominantly as irregular shape compounds located mainly in grain interiors. Both the primary solid and high melting point precipitates of Mn-Al modified with Sr, acted as nucleation substrates for secondary α-Mg grains.

In the microstructures of slowly and rapidly cooled liquid of the immiscible alloy Fe30Cu32Ni10Si13Sn4B9Y2 two distinct regions were observed following arc melting and slow cooling, confirming that liquid/liquid phase separation had occurred. Rapid cooling from a temperature within the liquid immiscibility gap, melt spinning, resulted in an amorphous/crystalline composite, formed from the previously melted Fe- and Cu-rich regions, respectively. Transmission electron microscopic studies of this melt-spun ribbon revealed the glassy nature of the Fe-rich matrix, as well as of the Fe-rich spheres formed within the previously existing Cu-rich liquid.

Analytical electron microscopy, supported by microchemical and microdiffraction techniques, was applied to assess the microstructural changes accompanying semisolid molding of a creep-resistant magnesium alloy with nominal chemistry of Mg–5%Al–2%Sr. In an ingot precursor, the Sr containing precipitates exhibited a morphology of Al 4 Sr platelets within eutectic colonies and Al–Mg–Sr films, both residing at grain/cell boundaries, while sub-boundaries were occupied by fine Mg 17 Sr 2 plates. Trace quantities of Mg 17 Al 12 were present as plate-shaped continuous precipitates within selected grain/cell interiors. Semisolid processing of mechanically comminuted ingots generated thixotropic morphologies with globular solids of α-Mg, having well-developed sub-structures. The quickly-solidified liquid fraction, enriched in Al and Sr, led to the formation of increased volumes of a lamellae type Al 4 Sr phase, surrounding the secondary α-Mg. Traces of Mg 17 Al 12 still existed, predominantly as irregular shape compounds located mainly in grain interiors. Both the primary solid and high melting point precipitates of Mn–Al modified with Sr, acted as nucleation substrates for secondary α-Mg grains. The possible implications of semisolid processing on the creep behavior of magnesium alloys are discussed.

Microscopical techniques were used to provide the microstructural details and identify mechanisms governing phase and morphological transformations during the heating of Mg–8%Al–2%Zn pellets in solid and semisolid states. It was found that an as-extruded matrix of equiaxed α-Mg grains with a twinning substructure, was thermally unstable and experienced complete recrystallization after reheating to 200 °C. The precipitates of the Mg 17 Al 12 phase and augmented concentrations of alloying elements within migrating grain boundaries and triple junctions played a key role in transformation of the equiaxed grains into thixotropic structures during partial melting. A direct link exists between sizes of equiaxed grains in the solid state and unmelted particles in the semisolid slurry. Although the morphology of primary solid particles did not change during the melting progress, the rate of particles’ coarsening at high temperatures and their internal microstructure in subsequently solidified alloy were influenced by the solid–liquid ratio. The importance of these findings for semi-solid injection molding practice is emphasized.

In the present work, the 316L steel+2%TiB2 powders are sintered after milling by High Pressure-High Temperature (HP-HT) process. Studies cover the effect of sintering parameters on the development of microstructure and properties. The microstructural evolution of 316L steel-2TiB2 composites is characterized by the techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It is found that the structure of a mixture of the 316L steel+2%TiB2 powders after milling and the structure of subsequent composites sintered by HP-HT is composed of a two-phase matrix including austenite (γ) and martensite (α'). The phase analysis and calculations of the martensite (α') content have revealed the highest content of this constituent in the matrix of 316L steel+2% TiB2 composites obtained by sintering at a temperature of 900 °C.

Przedstawiono wyniki obserwacji wizualnych, badań makro i mikroskopowych oraz pomiarów twardości złączy doczołowych blach ze stali 7CrMoVTiB10-10 (T24). Złącza spawane wykonano łukiem krytym, wiązką laserową i metodą hybrydową (wiązka laserowa + spawanie łukowe elektrodą topliwą w osłonie gazów). Obserwacje wizualne pozwoliły na ujawnienie nielicznych niezgodności spawalniczych, których obecność została potwierdzona w badaniach makroskopowych. Badania mikroskopowe nie wykazały istotnego wpływu technologii spawania na mikrostrukturę SWC, natomiast spoiny uzyskane w poszczególnych procesach charakteryzowały się zróżnicowaną mikrostrukturą, determinowaną m.in. szybkością odprowadzania ciepła. Pomiary twardości wykazały, iż niezależnie od zastosowanej technologii maksymalna wartość twardości przekracza 350 HV10. Abstract The paper presents the results of visual observation, macro- and microscopic examination and hardness testing of butt-welded joints of 7CrMoVTiB10-10 steel. Welded joints was made by Submerged Arc Welding, Laser Beam Welding and a hybrid method (Laser Beam Weld- ing + Gas Metal Arc Welding). Visual observation shown the presence of a few imperfections, what confirmed the macroscopic examination. Microscopic examination shown no significant effect of welding processes in the HAZ microstructure, while weld metal obtained by different processes is characterized by varied microstructure, that is determined i.e. heat removal rate. Hardness measurement shown that maximum hardness value exceed 350 HV10, regardless of welding process.

W pracy przedstawiono właściwości i strukturę połączenia spawanego pomiędzy elementem ze stali eksploatowanej 14 MoV6-3 oraz elementem nowym, nieeksploatowanym, również ze stali 14 MoV6-3. Oba elementy w postaci płyt o wymiarach 110x220x20 mm połączono dwoma metodami spawania łukowego. Grań spoiny wykonano metodą spawania elektrodą nietopliwą w osłonie gazu obojętnego (TIG), natomiast wypełnienie metodą spawania elektrodą otuloną (MMAW). Pospawany element został poddany wyżarzaniu odprężającemu. Powstałe złącze spawane zostało poddane badaniom nieniszczącym: VT, PT, RT oraz badaniom niszczącym: badaniu udarności, rozciąganiu złącza, badaniom metalograficznym oraz badaniu rozkładu twardości w złączu. W wyniku badań ustalono, iż istnieje możliwość wykorzystania zastosowanych metod spawania do wykonywania remontów lub modernizacji instalacji energetycznych Abstract The paper presents the structure and properties of the weld joint between the operated steel 14MoV6-3 and a new, non-operated steel 14MoV6-3 element. Both elements in the form of plates of dimensions 110 x 220 x 20 mm were joined by two methods of arc welding. Ridge welds made by welding tungsten inert shielding gas TIG, while filling was made by welding with coated electrode MMAW. Welded item has been heat treated stress-relief annealing. The resulting joint has been subjected to non-destructive testing: VT, PT, RT and destructive testing: impact test, tensile joints, metallographic examination and testing of hardness distribution in the joint. The research found that there is a possibility to use the methods of welding for repair or upgrading of power plants structures.

Thixomolding 1 , an emerging semisolid technology, was used to process an AZ91D magnesium alloy under experimental conditions designed to yield from 5 to 60% of the primary solid particles. The thixotropic microstructures obtained were characterized in detail and linked to the corresponding tensile properties. An increase in primary solid content was accompanied by its larger microchemical and microstructural inhomogeneity expressed by Al and Zn segregation, sub-micron precipitates of Mg 17 Al 12 and eutectic islands. At the same time, the size of α-Mg grains within the eutectic mixture was reduced. For the volume fraction of the primary solid up to about 20%, the tensile strength and elongation remained at the level of 240 MPa and 4.5%, respectively. A further increase of the primary solid caused a reduction in both strength and ductility. The fractographic analysis revealed a correlation between the primary solid content and the morphology of the decohesion surface. It is concluded that for alloys with a solid fraction below approximately 20%, the internal structure of the primary solid and the eutectic mixture control the properties. For a large volume of unmelted fraction, the interface between the primary solid and the eutectic mixture is a key factor which controls the tensile properties of the thixomolded alloy.

The microstructural parameters (dislocation density, martensite lath width, precipitate diameters, and volume fractions) have been measured for the 9%Cr steel P92 (NF616) after different heat treatments. The austenitising temperatures were 970, 1070, and 1145°C and the tempering temperatures 715, 775, and 835°C. Increasing the austenitising temperature led to an increase in the austenite grain size and in the martensite lath width, but no significant effect on the tensile properties at 20, 600, and 650°C was observed. The creep strength was, however, reduced by tempering at 835°C due to rapid recovery of the martensitic structure with a sharp decrease in dislocation density. The lowest creep strength was found for the P92 steel subjected to a heat treatment that produced a fully ferritic microstructure; the secondary creep rate was four orders of magnitude higher than that of the steel in the usual martensitic condition.

Thermal evolution of the crystallographic texture and microstructure in Ni electrodeposits, with a specific application for replication of optical recording devices, was examined. As-deposited microstructure was comprised of bimodal grains with a size of 4 and 0.1 μ m and the 〈100〉 fibre texture with inhomogeneous strength across the deposit thickness. The 〈100〉 texture was unstable and transformed during annealing to the 〈211〉 fibre. The texture transformation was accompanied by grain growth and deposit softening and the temperature range for rapid changes of all parameters was between 623 and 673 K. A numerical analysis of texture data was conducted to identify the type of Ni grain boundaries, which control grain growth and texture transformation. The microstructural observations suggested that the growth of grains with new orientation starts in fine-grained regions and controls the thermal stability of the entire deposit. The results are discussed in terms of the mechanism of texture transformation during annealing.

The hot-rolled plates of AISI 304 stainless steel, containing edge cracks of different intensities, were examined. The austenitic matrix of the steel contained small amounts of δ ferrite inhomogeneously distributed across the width and the thickness of the plate. A correlation was found between ferrite content and edge cracking: the higher the ferrite content the longer the edge cracks. Among the chemical elements present in the steel, the most critical effect on δ ferrite content was exerted by carbon and nitrogen. The longest edge cracks were observed for plates with the lowest content of carbon and nitrogen. A possible contribution of steel chemistry and heating temperature to changes in the steel phase composition and the probability of edge cracking is discussed.

Japanese 9% Cr steel containing 0.5% Mo and 1.8% W (P92) has been investigated. Quantitative microstructural analyses using TEM of thin foils and extraction double replicas have been carried out after different austenitization and tempering treatments and after creep deformation at 600 and 650°C. Statistical quantitative analyses were undertaken to determine the dislocation density within the martensite laths, the width of the martensite laths/subgrains and the size and distribution of the carbide and carbonitride precipitates. Correlation of the results of the microstructural investigation with the creep rupture properties allowed the stability of the microstructure during the high temperature exposure to be assessed. The consequences of microstructural changes for the extrapolation of creep rupture data to design lifetimes are considered. Taking into account the strengthening mechanisms which remain effective in long term testing, the 100000 h stress rupture strength of P92 at 600°C is estimated at 115 MPa.

Austenitic stainless steels are substantially harder during hot-rolling than either ferritic or mild steels. The objective of this study is to verify the possible correlation between the edge-crack formation during hot-rolling and the presence of {delta} ferrite in austenitic stainless steel. Hot-rolled plates of austenitic stainless steels, examined at room temperatures, contain up to 9% of {delta} ferrite in austenitic matrix. The distribution of ferrite in steel plate is inhomogeneous: the highest ferrite content is located in the vicinity of the plate edge. Moreover, the content of {delta} ferrite changes irregularly across the plate thickness. The results obtained from analysis of several plates suggest a correlation between the maximum content of {delta} ferrite in steel microstructure and the length of the edge-crack formed during hot-rolling: the higher the volume fraction of ferrite, the longer the edge-crack.

Microstructural investigations of the steel 9Cr0.5Mo2W (NF616), a Japanese steel developed for advanced power station components, have been carried out by optical microscopy and by transmission electron microscopy, using thin foils and extraction replicas prepared after normalization at 970–1145°C and tempering at 715–835°C. After normalization, the steel exhibited a martensitic structure with only small amounts of retained austenite. During tempering recovery and precipitation processes occurred which reduced the hardness of the martensite. Elongated martensite laths were observed within the prior austenite grains, the boundaries of which were decorated with M 23 C 6 precipitates. In addition to the M 23 C 6 precipitates, three types of MX (where X is C and/or N) precipitate were detected; spheroidal Nb-rich carbonitrides, plate-like V-rich nitrides and complex particles consisting of the plate-like particles nucleated on the spheroidal ones. Statistical analyses of the microstructure were carried out using both thin foils and extraction replicas to determine the subgrain size and the particle size distributions and relate them to the heat treatments.