High-entropy alloys, due to their unique characteristics and complex chemical compositions, offer promising potential for a wide range of practical applications, particularly at elevated temperatures. The continuous development of these materials is driven by ongoing research on new manufacturing methods, with a large share of in-situ alloying from elemental powders in additive manufacturing processes. In addition, their complex chemical compositions provide a variety of heat treatments application, offering opportunities for tailoring properties of HEAs. In this study, four alloys based on Mn-Fe-Co-Ni with varied additions of Ti and Al and entropy levels were produced using the Laser Powder Bed Fusion technique from elemental powders mixtures and subjected to several heat treatment routes, followed by a comparative evaluation of their microstructure, hardness and yield strength in uniaxial compression tests. It was found that in Mn-Fe-Co-Ni+5Al+5Ti, precipitation strengthening via the γ’ phase (Ni, Co)₃(Ti, Al) could be achieved through appropriate heat treatment. Importantly, the results indicate that γ’-strengthened alloys have significant potential for high-temperature applications, with compressive yield strength reaching 621 MPa after 15 min of exposure at 700 °C.

This study investigates the mechanical behaviour of fused filament fabrication (FFF) of 316L austenitic stainless steel compared to conventional 316L at room temperature and 77 K, focusing on deformation-induced martensitic transformation (DIMT). Results reveal that the L & uuml;ders-like effect, present in conventional 316L at 77 K, is absent in FFF 316L due to porosities that hinder martensitic front propagation. At room temperature, uniform strain distribution and DIMT were observed in conventional 316L, whereas in FFF 316L, martensitic nucleation occurred around pores, serving as a localized strengthening mechanism. Microstructural analysis identified Fe-delta islands along grain boundaries in FFF 316L, which contribute to its multiphase nature. Although FFF 316L demonstrates lower yield stress and elongation compared to conventional 316L, this study does not establish design allowables. The present findings are limited to monotonic tensile behaviour, fatigue performance and corrosion resistance under cryogenic conditions were not assessed. Further optimization of fabrication parameters to minimize ferrite content and porosities is suggested to enhance mechanical performance.

In this study, the evolution of residual stress and elastic anisotropy in 17–4 PH stainless steel produced by atomic diffusion additive manufacturing (ADAM) and then subjected to surface mechanical attrition treatment (SMAT) was investigated. Angle- and energy-dispersive X-ray diffraction techniques were employed to analyse the residual stress profiles in both the as-built and SMAT-processed samples. The results reveal that SMAT introduces compressive residual stresses while refining the material subgrain structure. Residual stress analysis indicates that the as-built sample exhibits tensile stresses near the surface, which gradually decrease with depth. In contrast, the SMAT-processed sample shows compressive stresses, ranging from −200 MPa at the surface to −600 MPa in deeper regions. This study highlights the critical role of selecting an appropriate grain-interaction model for X-ray stress factor calculation to ensure accurate residual stress characterization, which is essential for the reliability and performance of additively manufactured components, particularly applications with high-level loading.

The microstructure-properties relationship of the low-alloy, high-carbon nanostructured bainitic steel obtained by heat treatment, including austenitization and cooling followed by isothermal nanobainitic transformation at 280℃ for 72 h, was investigated. Detailed characterization of the obtained microstructure was performed using light optical, scanning, and transmission electron microscopy. These analyses reveals that the microstructure of tested nanobainitic steel consists of bainitic ferrite lath with an average size of 84 ± 21 nm and retained austenite with two different morphologies: (i) thin films with an average size of 64 ± 19 nm and (ii) blocks with a size of a few micrometers. The carbon concentrations in the film-type retained austenite and blocks of retained austenite were determined through X-ray synchrotron radiation diffraction analysis. The concentrations are 1.81 ± 0.09 wt.% and 1.39 ± 0.06 wt.%, respectively. The total amount of retained austenite in the microstructure is 48.0 ± 1.8 vol.%, and the dominant crystallographic orientation relationships between the microstructure constituents were determined to be Nishiyama-Wassermann. The minor K-S relationship was also recognized from the SEM/EBSD results. Tensile strength of the nanostructured steel was tested, and yield strength was found to be high. At an elongation of 7.2%, the tensile strength reached a significant level, while the average hardness was 490 ± 7 HV.

In this work, the influence of chromium and titanium on the microstructure and mechanical properties of cast steel is investigated. The analysis was carried out on a material covered by patent Pat.243157. Advanced techniques were used, including dilatometric analysis, light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The material was examined in various states: as-cast, quenched, and quenched with subsequent tempering at 200 degrees C, 400 degrees C, and 600 degrees C. Important mechanical properties such as hardness, yield strength, percentage elongation, percentage reduction in area after fracture, and impact toughness at temperatures ranging from -40 degrees C to +20 degrees C were evaluated. The results were compared with those of a reference cast steel without these alloying elements, allowing a detailed assessment of the influence of chromium and titanium. The investigation begins with a comprehensive literature review of the effects of these elements in iron-based alloys. The results highlight the influence of chromium and titanium on the mechanical properties and microstructural development of cast steel. These elements play a critical role in enhancing mechanical strength, particularly after quenching and tempering, although there are evident trade-offs in ductility and impact toughness. In addition, the study discusses the damage mechanisms, focusing on the role of titanium nitrides in the cracking process.

AISI 304 steel experiences plastic flow instability during tension at room temperature if appropriate conditions are applied: a low strain rate and a sufficiently long gauge section of the sample. Then, propagation of the strain-localised band is activated. The electron backscattered diffraction (EBSD) research revealed that the reason is not only the difference in the content of the secondary phase - martensite alpha' across the front face, but also the change in the volume fraction of austenite grains with Copper (Cu) and Goss-Brass (GB) orientation. Consequently, there is a division between two areas of high and limited deformation capacity. The tendency to maintain the continuity of deformation fields induces a massive rotation of austenite grains to Cu and GB orientations, which then undergo shearing and phase transformation. As a result, momentary strain accumulation leaves behind a stiffer zone. It is shown that the trapping of austenite grains prone to large deformations, inside the matrix with Cu and GB orientations, makes the formation of a plastic strain front possible. These features improve the ductility and strength of the 304 steel over 316L and 316LN at room temperature. The in-situ EBSD tension studies for the considered grades reveal three developing textures, with their comparison showing a gradual decrease in the preferences of the Cu and GB components. Thus, the appearing bands of the accumulated strains in 316L are limited by the Cu and GB areas, while such blockages do not occur in 316LN. The presented strengthening mechanism is confirmed by the digital image correlation (DIC) measurements. The root-mean-square (RMS) function of strains along the tensile direction, characterising the linear surroundings of the considered point, is introduced as a tool for linking the micro and macro scales. The experimental results provide a basis for explaining discontinuous front propagation at a temperature near 0 K.

In this work, the influence of Mo in the CoNiFeMn system during heat treatment after prior hot and cold rolling was investigated. At present, relatively few studies on static recrystallization and grain growth kinetics in high entropy alloys are available. This paper focuses on static recrystallization and grain growth kinetics as well as the influence of molybdenum on these phenomena. This work compares two alloys, CoNiFeMn and (CoNiFeMn)95Mo5, in relation to the formations of the brittle µ phase at room- and high-temperature plastic deformation regimes due to its negative affect on material ductility. Microstructures were characterized by energy dispersive X-ray spectroscopy analysis and by scanning electron microscopy, whereas the mechanical properties were assessed by tensile testing. The effect of recrystallization and grain growth behaviours on the microstructural evolution and the final mechanical properties was assessed. It was found that Mo addition into the CoNiFeMn system has a strong effect on both the static recrystallization and grain growth kinetics as well as the final mechanical properties.

Ni-Co-Fe-Mn-Ti high entropy alloys (HEA) were fabricated via powder bed fusion using elemental powders. Based on thermodynamic calculations, 3 alloys were designed with medium to high entropy (from 3 to 5 components) and printed. Additive manufacturing (AM) was performed, while varying the laser power and exposure time (point-by-point exposure laser working mode). The obtained samples were characterised by means of macroscopic observations combined with porosity analysis, scanning electron microscopy (SEM), energydispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), as well as compression and hardness tests. The varied process parameters and the content of individual alloying elements directly impacted alloy processability and sample properties. We proved that it is possible to produce HEAs (NiCo-Fe-Mn-Ti) with low porosity and good chemical homogeneity from elemental powders. By comparing the processes of producing 3-, 4-, and 5-component alloys, it was observed that it is not the quantity of the components but the melting temperatures of the individual elemental powders and their tendency to oxidise that affect obtaining good 3D prints. The most promising results for 5-component HEAs were obtained for 145 mu s of laser exposure time combined with laser powers of 250 and 300 W.

This research aimed to produce high-entropy alloys (HEA), namely Mn–Fe–Co–Ni + 5Al and Mn–Fe–Co–Ni + 5Al + 5Ti, through the Powder Bed Fusion technique using elemental powders. Alloy composition has been selected to achieve a HEA matrix with strengthening intermetallic precipitates. Thermo-Calc software has been used to predict solidification behavior and phase stability for non-equilibrium conditions. The experiment involved the execution of an additive manufacturing process with a laser working in point-by-point exposure mode to produce samples using varying laser power and exposure time. The samples underwent investigation via macroscopic examination, porosity analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and hardness testing. Results have shown that processing parameters and alloy constituents directly influenced processability and sample traits. What is more, a high-energy laser beam introduction to the material during the process has helped mitigate the formation of large Ti or Al oxides. In addition, EDS analysis indicated that higher Volumetric Energy Density values enhanced the uniformity of chemical composition, indicating that homogeneity can be achieved by selecting appropriate melting parameters. The results clearly show that these alloys can be successfully (by means of porosity and homogeneity) manufactured from elemental powders via the powder bed fusion technique.

A remarkable plastic flow instability is observed during tensile deformation of the commercial 304 stainless-steel sheet at room temperature. It has been found that the occurrence of plastic flow instability in 304 is dependent on the strain rate and specimen gage length. Moreover, it is essentially the same as the necking caused by plastic instability in 316L. However, the enhanced strain hardening resulting from deformation-induced martensitic transformation facilitates the orderly propagation of the strain-localized band.

H11 hot work tool steel (1.2343) belongs to the most commonly used materials in the tooling industry, with significant heritage in producing extrusion dies or injection molds. Those components often are characterized by complex geometries, which makes them a great candidate for additive manufacturing. However, the hot working steel is hard to process by additive manufacturing technologies due to its cracking susceptibility related to high cooling rates occurring during printing. A potential way to reduce cracking tendencies is to utilize a point-bypoint laser scanning methodology which influecnes the thermal conditions of the process. To prove this, a series of samples were produced via Powder Bed Fusion with various manufacturing parameters and without build platform preheating. Produced samples have been investigated by light and scanning electron microscopy methods, X-ray analysis, and hardness tests. The obtained results indicate that the use of short laser pulses in Powder Bed Fusion can limit the cracking in printed parts. In addition, the laser pulses play an important role in shaping the microstructure of the processed H11 hot work tool steel. The optimal parameters limiting the crack density to 6 mm-2 with 0.1 % porosity in H11 steel printouts were determined.

This paper presents studies concerning the influence of the Ga+ ion beam on the stability of retained austenite in K110 cold work tool steel (X155CrVMo12). The material was first austenitized at 1200 C to dissolve a significant amount of the alloy's carbides to obtain the largest possible volume fraction of retained austenite, which was 93% after quenching in oil. Changes in the steel's crystal structure upon interaction with Ga+ ions were observed using a combination of SEM-FIB-EBSD techniques. Selected grains in the material were sputtered with Ga+ ions of various accelerating voltages (2 kV - 30 kV) using two different doses, namely 50 and 100 pC/mu m(2). It was found that the application of 5 kV Ga+ ion beam is enough to induce partial transformation of austenite to BCC phase. The use of higher voltages (8-30 kV) resulted in the complete transformation of austenite. Low acceleration voltages of 2 kV, even with a high dose of 500 pC/mu m(2), did not induce any phase transformation and only deformed austenite's crystal structure. Moreover, it was shown that the crystallographic orientation between austenite and the Ga+ ion beam induced BCC phase is not random.

The evaluation of the nanoindentation test capabilities in the investigation of mechanical material behaviors of TiN thin films deposited on the different substrates is the primary goal of the research. This particular work is focused on the determination of flow stress characteristics and fracture behaviors of TiN thin films based on a series of nanoindentation tests and finite element calculations. TiN films obtained by the Pulsed Laser Deposition were selected as a case study for the investigation [1]. They were deposited on the different substrate materials and investigated through the nanoindentation test. To properly recalculate measured load-displacement values into the required stress-strain curve and to determine fracture initialization and propagation factors, a finite element approach is used. Subsequent stages, including deposition process of TiN thin film, room temperature nanoindentation tests, and development of a numerical model which takes into account concept of the digital material representation (DMR) and cohesive zones type elements [2,3] are described in this work. Examples of obtained results presenting capabilities of the proposed approach are also highlighted.

In this work, the effect of topologically close-packed chi phase on the microstructure and properties of the rapidly solidified hypoeutectic iron-based Fe-25Cr-7Mo-0.8C alloy was investigated. The novelty of the work is based on the introduction of y phase into the Fe-based hypoeutectic alloy with the aim of reducing the mean free path of the matrix and increasing abrasive resistance. The phase composition was studied using in situ neutron and ex situ X-ray synchrotron diffraction. The microstructural evolution was analyzed via scanning and transmission electron microscopy and modelled using CALPHAD thermodynamic calculations. The mechanical behavior of the evolving microstructure was quantified using high-speed nanoindentation mapping. At low temperatures (650 degrees C), the chi phase nucleates mainly in dendrite areas and exhibits a needle-like morphology caused by high misfit with the ferritic matrix. At higher temperatures (800 degrees C), the chi phase nucleates on carbide/matrix interfaces and in dendrites and is characterized by a blocky morphology. Simultaneously, the evolution of M23C6 carbide morphology towards a continuous and solid network of precipitates was observed. Such changes in the alloy's microstructure induced an increase in hardness of about 16% and resulted in the reduction of the average scratch depth in comparison to as-cast state. (C) 2019 The Authors. Published by Elsevier Ltd.

The Ti-6Al-4V alloy wires were plastically deformed using the accumulative angular drawing (AAD) process at room temperature with a maximal logarithmic strain epsilon similar to 0.51. Microstructure and microtexture evolution and inhomogeneity of the Ti alloy wires were investigated quantitatively using the electron backscattered diffraction technique within the scanning electron microscope and compared to wires after conventional linear drawing. Moderate grain refinement was observed after deformation. The kernel average misorientation parameter increased significantly, pointing to evolution of subgrain structure. The yield stress and ultimate tensile strength increased after the AAD and linear drawing and decrease in hardness was observed after the first pass of the AAD and linear drawing process. However, the AAD introduced inhomogeneity in hardness values at the sample cross section. Hardness variation correlates with a local texture asymmetry parameter, while no correlation between hardness and grain size was observed. A Schmid factor analysis indicated that the AAD is inhomogeneously introducing grain orientations that are favorable for prismatic and pyramidal dislocation slip, having a positive effect on the plasticity of Ti-6Al-4V alloy wire during drawing.

The present work was undertaken to determine the effect of nickel on the microstructure in rapidly solidified similar to Fe-25Cr-xNi-5Mo-0.8C alloys. The alloys were synthesised via arc melting and rapidly solidified using the suction casting technique. Phase composition was investigated using synchrotron x-ray diffraction and the solidification range was determined by means of differential scanning calorimetry. The microstructure in as-cast state was analysed using scanning electron microscopy. Properties were investigated by hardness measurements and scratch tests using the nanoindentation technique. The obtained results were discussed with respect to thermodynamic calculations, carried out using the CALPHAD approach. It was observed that with increasing nickel contents the average dendrite size, mean free path of the matrix and the spacing between the lamellar carbides, as well as the regularity and thickness of the carbides decreased. With decreasing mean free path of the matrix a decrease of average scratch depth occurred. This corresponds to abrasive wear, i.e. in alloys having smaller average dendrite size, abrasive particles will more frequently encounter eutectic areas with greater hardness than the matrix. As a result, the material exhibits greater abrasive wear resistance. The results presented in this work show that there is a possibility to enhance abrasive wear resistance of hypoeutectic iron-based alloys by modifying their chemical composition and, in turn, reducing the mean free path of the matrix. (C) 2019 Elsevier B.V. All rights reserved.

The paper presents a multi-scale mathematical model dedicated to a comprehensive simulation of resistance heating combined with the melting and controlled cooling of steel samples. Experiments in order to verify the formulated numerical model were performed using a Gleeble 3800 therm-mechanical simulator. The model for the macro scale was based upon the solution of Fourier-Kirchhoff equation as regards predicting the distribution of temperature fields within the volume of the sample. The macro scale solution is complemented by a functional model generating voluminal heat sources, resulting from the electric current flowing through the sample. The model for the micro-scale, concerning the grain growth simulation, is based upon the probabilistic Monte Carlo algorithm, and on the minimization of the system energy. The model takes into account the forming mushy zone, where grains degrade at the melting stage - it is a unique feature of the micro-solution. The solution domains are coupled by the interpolation of node temperatures of the finite element mesh (the macro model) onto the Monte Carlo cells (micro model). The paper is complemented with examples of resistance heating results and macro- and micro-structural tests, along with test computations concerning the estimation of the range of zones with diverse dynamics of grain growth.

The microstructure and properties of cast and hot-rolled Al5Ti5Co35Ni35Fe20 High-Entropy Alloy were studied. Presented alloy after initial homogenization for 20 h at 1100 degrees C is characterised by gamma/gamma' structure. After solid solution annealing at 1200 degrees C gamma' precipitates were dissolved that allowed further hot plastic deformation. Heat treatment performed after hot-rolling were used to increase the strength by gamma' precipitation strengthening. Tensile testing was performed at 20 degrees C, -120 degrees C and -196 degrees C. Deformation mechanisms observation was conducted by means of SEM-EBSD and TEM. To evaluate the mechanical properties after solid solution treatment the sigma(y0.2) and sigma(u) at 20 degrees C were measured approx. 775 MPa and 1045 MPa, respectively. The decrease in temperature to -196 degrees C increase mentioned above parameters of about 20%. Precipitation strengthening enhances the sigma(y0.2) and sigma(u) up to 900 MPa and 1200 MPa at room temperature and to 1020 MPa and 1460 MPa at -196 degrees C, respectively. Investigated alloy exhibits a high elongation to failure over 18% regardless of heat treatment and deformation temperature. Despite the face-centers cubic crystal structure and high Co, Fe and Ni content the twinning were not observed. Deformation behaviour at all testing temperature was the same, the main deformation mechanism was dislocation slip.

Digital Material Representation (DMR) concept in application to numerical investigation of the two different types of epoxy/glass composite morphologies under loading conditions is addressed within the paper. First, two algorithms for reconstruction of digital microstructures based on metallography investigations are developed. Then, material properties of the investigated epoxy matrix and glass fillers are evaluated based on an in-situ tensile test as well as nano-indentation, respectively. At this stage a numerical investigation is also extended by series of experimental tensile tests to understand basic mechanisms occurring during deformation of the two different types of glass particles fillers. Finally, an example of practical application of the developed digital microstructure model for multi scale calculations of the epoxy/glass composite under loading is presented.

In the present work, the concept of hypoeutectic Fe-Cr-Ni-Mo-C alloys additionally strengthened by the Frank-Kasper phases is shown. The alloys were designed using the CALPHAD approach in order to obtain a matrix with high corrosion resistance, similar to that of stainless steels, and good wear resistance at room and elevated temperatures, achieved by the precipitation of eutectic carbides and the Frank-Kasper phases. The main design strategy is to produce alloys with a narrow solidification range and precipitations of the Frank-Kasper phases within the dendrites after heat treatment in order to reduce the mean free path of the matrix. The effect of molybdenum on the evolution of intermetallic phases in the Fe-25Cr-xMo-0.8C system was determined. Additionally, the influence of nickel in the Fe-25Cr-5Mo-xNi-0.8C system on phase composition of the matrix, as well as the stability and volume fraction of intermetallic phases were investigated. Lever-Rule and the modified Scheil-Gulliver solidifications were simulated for selected five alloys in order to investigate the phase precipitation sequence. Particular emphasis during the discussion was placed on the influence of Mo and Ni on phase stability, as well as solidus and liquidus temperatures in the investigated systems.