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This paper presents the results of a pilot application of Powder-Bed Fusion of Metals Using a Laser (PBF-LB/M) for the fabrication of M300 (1.2709) maraging steel sheet metal bending tools. S235 steel was used as a substrate for the fabrication of bending punches. The main goal of the research was to determine the usability of such tools without heat treatment, which would contribute to the increase in the cost of tool production. Industrial tests of tools were conducted during the forming of Inconel 625 and AW-6061 T0 aluminium alloy sheets. The punches were subjected to tests of surface roughness, hardness, microstructure, porosity, and geometric quality in order to verify the quality and accuracy of tools made by the PBF-LB/M technique before and after experimental investigations in industrial conditions in a selected manufacturing company. It was found that tools with an M300 steel working layer after the PBF-LB/M process without heat treatment show suitability for bending sheet metal in a certain range of force parameters, ensuring obtaining elements after bending from Inconel 625 and AW-6061 T0 aluminium alloy sheets of the required geometric quality. [ABSTRACT FROM AUTHOR]

The results of experimental and numerical studies of plastic forming of sheets made of the difficult-to-deform Hastelloy X, a nickel-based alloy with a thickness of 1 mm, using layered elastomeric punches and steel dies, are presented in this publication. The elastomeric punches were characterized by hardness in the range of 50–90 Shore A, while the dies were made of 90MnCrV8 steel with a hardness of over 60 HRC. The principle of operating the stamping die was based on the Guerin method. The finite-element-based numerical modeling of the forming process for various configurations of polyurethane inserts was also carried out. The results obtained from numerical modeling were confirmed by the results of experimental tests. The drawpieces obtained through sheet forming were subjected to geometry tests using optical 3D scanning. The results confirmed that in the case of forming difficult-to-deform Hastelloy X, Ni-based alloy sheets, the hardness of the polyurethane inserts significantly affected the geometric quality of the obtained drawpieces. Significant nonuniform sheet metal deformations were also found, which may pose a problem in the process of designing forming tools and the technology of the plastic forming of Hastelloy X, Ni-based alloy sheets. [ABSTRACT FROM AUTHOR]

This study investigates the influence of solution treatment temperatures on the microstructure and mechanical properties of LPBF (Laser Powder Bed Fusion)-manufactured Inconel 939 alloy. The primary objectives are to assess the impact of sub-recrystallization (below recrystallization temperature) and recrystallization temperatures during solution treatment on mechanical performance under different conditions. This study validates the hypothesis concerning carbide redistribution and mechanical performance in LPBF-produced Inconel 939 parts through comprehensive analysis, including microstructure studies and tensile tests. The results indicate that higher heat treatment temperatures lead to significant changes in carbide redistribution and mechanical performance. For instance, at room temperature, the specimen with sub-recrystallization solution treatment temperature exhibited superior mechanical properties compared to both the as-built and recrystallization-temperature solution treatment specimens. However, at elevated temperatures (700 °C), a reversal in mechanical anisotropy was observed, with the vertical axis demonstrating higher tensile strength compared to the horizontal axis for all material states. Furthermore, a microstructural analysis revealed distinct changes in grain structure and precipitate distribution, particularly the migration of carbides from grain boundaries to intragranular regions. These findings underscore the importance of precise control over heat treatment parameters to achieve optimal mechanical behavior. This research provides valuable insights into optimizing LPBF processes for the Inconel 939 alloy, highlighting the need for a meticulous control of the solution treatment parameters to ensure mechanical integrity. The findings contribute to a broader understanding of material-specific responses in additive manufacturing, with significant implications for aerospace applications. [ABSTRACT FROM AUTHOR]

This paper presents a continuous severe plastic deformation (SPD) process for sheet metal called Dual Rolls Equal Channel Extrusion (DRECE) is introduced. The DRECE process achieves maximum sheet metal deformation by combining bending deformation with channel-angular shear deformation. The evolution of the microstructure and mechanical properties of the CuZn37 alloy has been experimentally investigated as a function of the number of repeated DRECE passes. The DRECE process was repeated up to four times at room temperature. As the number of passes increased, the character of the microstructure was gradually strongly deformed by intensive shear deformation. The microhardness and tensile properties changed significantly as a function of the number of repeated passes. [ABSTRACT FROM AUTHOR]

In this study, the relationship between the extrusion ratio and the corrosion resistance of pure Mg deformed using extrusion with an oscillating die (KoBo) without preheating of the initial billet was investigated. The materials investigated in this study were extruded at high deformation ratios, R1 5:1, R2 7:1, and R3 10:1, resulting in significant grain refinement from the very coarse grains formed in the initial billet to a few µm in the KoBo-extruded samples at room temperature, which is not typical for hexagonal structures. Our research clearly shows that KoBo extrusion improves the corrosion performance of pure Mg, but there is no straightforward dependence between the extrusion ratios and corrosion resistance improvement. Although it was expected that the smallest grain size should provide the highest corrosion resistance, the dislocation density accumulated in the grain interiors during deformation at the highest extrusion ratio, R3 10:1, supports dissolution reactions. This, in turn, provides the answers for the greater grain size observed after deformation at R2 7:1, where dynamic recovery prevailed over dynamic recrystallization. This situation led to the annihilation of dislocation, leading to better corrosion resistance of the respective alloy. Therefore, the alloy with the greatest grain size has the best corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the possibilities of improving the mechanical and corrosion properties of Mg–4Li–1Ca processed using twist channel angular pressing (TCAP) were investigated. There was a special focus on the optimization of the TCAP parameters through analyzing how the temperature of TCAP influences the microstructural, mechanical, and corrosion properties of the alloy, and how an increasing number of TCAP passes affects these properties. It was shown that among specimens extruded with one pass, the highest mechanical properties were achieved at 180 °C. Microstructural changes were noted at higher temperatures and caused a decline in the mechanical properties. The influence of an increasing number of passes through the TCAP channel was rather minor and did not lead to significant microstructural strengthening. In contrast, the best corrosion performance was observed after four passes at 180 °C and after a single pass at 300 °C. The results of this study show that TCAP is an efficient method for the grain refinement of hcp-structured metals, lowering the costs of the plastic deformation of Mg-based alloys. [ABSTRACT FROM AUTHOR]

In this study, we examined the effects of an aluminization process on the microstructure and texture of Haynes 282 nickel samples fabricated using the direct metal laser sintering technique. The aluminization process involved the use of chemical vapor deposition with AlCl3 vapors in a hydrogen atmosphere at a temperature of 1040 °C for 8 h. Following the 3D printing and aluminization steps, we analyzed the microstructure of the Haynes 282 nickel alloy samples using light microscopy and scanning electron microscopy. Additionally, we investigated the texture using X-ray diffractometry. A texture analysis revealed that after the process of direct laser sintering of metals, the texture of the Haynes 282 nickel alloy samples developed a texture typical of cast materials. Then, in the aluminization process, the texture was transformed—from foundry-type components to a texture characteristic of recrystallization. [ABSTRACT FROM AUTHOR]

The Friction Stir Welding (FSW) method was employed to join AA6082 sheets. The welds were produced with different tool traverse speed (200 and 250 mm/min), rotational speed (1000 and 1250 RPM) and tool tilt angle (0 and 2 deg). Based on the analysis of XRD patterns, the total precipitation volume fractions in the nugget zones and the base material were calculated. The FSW process resulted in a reduction in the fraction of precipitates up to 64 pct compared to the parent material. Based on the Williamson–Hall analysis and indentation tests, the residual stresses were calculated. The highest tensile residual stresses of − 89.09 ± 6.19 MPa were observed for the base material, and the welding process reduced the residual stresses. The calculated dislocation density in the parent material AA6082 was equal to 8.225 × 1013 m−2, while in the welds a decrease was observed up to the value of 1.419 × 1013 m−2. In addition, the FSW process changed the nature of dislocations with edge-type dislocations dominating, while screw dominating character of dislocations were prevalent in the parent material. The mobility of dislocations in the studied welds was higher and reached the value of 16.78 × 10–7 m s , while the dislocation mobility in the parent material was equal to 3.19 × 10–7 m s . Process parameters during welding have a crucial effect on the amount of heat and strains introduced during the process, and thus influence the residual stresses, dislocation density and mobility, which might have a fundamental impact on the properties of the produced welds. [ABSTRACT FROM AUTHOR]

The article presents the results of research on the influence of plastic deformation on the microstructure and tensile strength of Haynes 282 nickel superalloy produced by direct metal laser sintering (DMLS) and a conventional technique (casting). Samples were tested for dimensional accuracy using a 3D scanner. Then, the samples were subjected to plastic deformation by rolling. The microstructures of the DMLS and the as-cast samples were analysed using a scanning electron microscope. The strength properties of the samples were determined in a static tensile test. Microhardness measurements of the samples were also performed. Based on the analysis of the dimensional accuracy, it was found that the surface quality of the components produced by DMLS is dependent on the input parameters of the 3D printing process. Using the DMLS method, it is possible to produce Haynes 282 with a fine-crystalline microstructure containing dendrites. The fine-crystalline dendritic microstructure and low porosity showed very good tensile strength compared to the as-cast material. It was also found that the increase in the degree of plastic deformation of the as-cast Haynes 282 and the samples produced by the DMLS technique resulted in an increase in the strength of the tested samples, with reduced ductility. [ABSTRACT FROM AUTHOR]

In this study, the microstructure-dependent corrosion of fine-grained Mg-4Li-3Al-Zn alloys in the chloride containing solutions is described. The materials were processed using extrusion with a forward-backward oscillating die. The Mg-4Li-3Al-Zn alloys were extruded from Ø40 to Ø4 mm (R1= 10:1, λ1 = 100), and also from Ø40 to Ø1 mm (R2= 40:1, λ2 = 1600); the resulting microstructures were then analyzed. The results show that the corrosion of both alloys is strongly dependent on the processing parameters (mainly extrusion ratio), which in turn have a significant influence on the recrystallization stage. Interestingly, the higher the extrusion ratio, the lower the corrosion resistance of the alloy. The decreasing corrosion resistance of the alloy deformed at a higher extrusion ratio is related to the grain growth resulting from the more intense recrystallization processes that occurred during KoBo extrusion. [ABSTRACT FROM AUTHOR]

The study examines the effect of the annealing on the microstructure, tensile strength (small flat dog-bone specimen size with 5 mm dimension of measuring base) and corrosion resistance of IN 625 nickel superalloy specimens manufactured by means of selective laser melting method (SLM). The annealing of such specimens was carried out in a chamber furnace in a protective atmosphere of argon at a temperature of 1038 °C for 1 h. The cooling process was carried out in an atmosphere of air at ambient temperature. The microstructure of the IN 625 nickel superalloy after the 3D printing process and after the post-process heat treatment (HT) was examined by means of scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed a uniform microstructure after the SLM process with element microsegregation. The cooling rate in the heat treatment was not sufficient which caused precipitation at the grain boundaries, most probably carbides and resulted in only a partial increase in ductility much lower than that of the material in initial state despite the high temperature applied during the annealing. The strength in the HT was on a level comparable to as-build state, 852 MPa and 891 MPa, respectively. Additional corrosion resistance tests were performed by the potentiodynamic method in a 3.5% NaCl solution at room temperature. HT increased the current density variation from ipass due to the formed precipitates. Our studies show that the size effect is an important factor when assessing the properties of IN 625 obtained using SLM. Despite similar microstructure, the structure defects play a more significant role which translates into lower mechanical properties than in normal sized specimens defined by the standard ASTM E8. [ABSTRACT FROM AUTHOR]

The present study investigates the correlation between mechanical properties and resistance to corrosion of hydrostatically extruded aluminum alloy 7075. Supersaturated solid solutionized samples undergo a plastic deformation process, followed by both natural and artificial aging. Furthermore, two types of hydrostatic extrusion are applied to the samples: single-stepped and double-stepped. This process is shown to influence grain refinement and the precipitation process, resulting in changes in the electrochemical properties of the samples. Hydrostatic extrusion combined with aging is shown to cause an increase in mechanical strength ranging from 50 MPa to 135 MPa in comparison to coarse-grained sample subjected to T6 heat treatment. The highest value of tensile strength is obtained for a sample subjected to single-step hydrostatic extrusion followed by natural aging. This strength increase is caused by refinement of the microstructure, in addition to the small size and number of precipitates at the grain boundaries, which are coarsened by artificial aging. Hydrostatic extrusion is also shown to increase resistance to corrosion, with the T6-treated coarse-grained sample being most susceptible to corrosion attack. [ABSTRACT FROM AUTHOR]

This paper presents the microstructural changes and mechanical properties of carbide-free bainitic steel subjected to various heat treatment processes and compares these results with similarly treated ferritic–pearlitic steel. A key feature of the investigated steel, which is common among others described in the literature, is that the Si content in the developed steel was >1 wt.% to avoid carbide precipitation in the retained austenite during the bainitic transformation. The phase identification before and after various heat treatment conditions was carried out based on microstructural observations and x-ray diffraction. Hardness measurements and tensile tests were conducted to determine the mechanical properties of the investigated materials. In addition, following the tensile tests, the fracture surfaces of both types of steels were analyzed. Changing the bainitic transformation temperature generated distinct volume fractions of retained austenite and different values of mechanical strength properties. The mechanical properties of the examined steels were strongly influenced by the volume fractions and morphological features of the microstructural constituents. It is worth noting that the bainitic steel was characterized by a high ultimate tensile strength (1250 MPa) combined with a total elongation of 18% after austenitizing and continuous cooling. The chemical composition of the bainitic steel was designed to obtain the optimal microstructure and mechanical properties after hot deformation followed by natural cooling in still air. Extensive tests using isothermal transformation to bainite were conducted to understand the relationships between transformation temperature and the resulting microstructures, mechanical properties, and fracture characteristics. The isothermal transformation tests indicated that the optimal relationship between the sample strength and total elongation was obtained after bainitic treatment at 400 °C. However, it should be noted that the mechanical properties and total elongation of the bainitic steel after continuous cooling differed little from the condition after isothermal transformation at 400 °C. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to obtain high-temperature-resistant material with high density and to conduct microstructural investigations of 3D-printed Ni-based alloy 713C specimens. Design/methodology/approach: High-density specimens of Ni-based alloy 713C were obtained by the optimizing selective laser melting (SLM) process parameters and an X-ray diffraction (XRD) analysis confirmed the occurrence of γ and γ′ phases and the presence of carbides in the SLM-manufactured Ni-based alloy 713C. The analysis of electron backscatter diffraction (EBSD) studies suggested a preferred 〈100〉 direction orientation and low angle misorientation for the SLM specimens. Findings: The high-density specimens of Ni-based alloy 713C were obtained by the optimized SLM process parameters. XRD analysis confirmed the presence of γ and γ′ phases and carbides in the SLM-manufactured Ni-based alloy 713C. Analysis of EBSD studies suggested a preferred 〈100〉 direction orientation and low angle misorientation for the SLM specimen. Originality/value: In this study, 3D-printed Ni-based alloy 713C with a high density of 99% was obtained for the first time, to the best of the authors' knowledge. [ABSTRACT FROM AUTHOR]

The aim of this study is to produce Ti–AlN via selective laser melting. The results show that the microstructure of the produced alloy is not uniform. The X‐ray diffraction measurements show that the Ti–AlN composite is composed of a Ti matrix, AlN compounds, as well as (TiN)0.88, Al6Ti19, and Al1.1Ti0.9 intermetallics. The as‐printed Ti–AlN is also composed of dendrites of two typical titanium nitrides (TiN and Ti2N) and titanium aluminum nitride (Ti2AlN). Subsequent quenching and annealing slightly change the phase composition of the alloy and is the main reason for their different corrosion behaviors in acidic and chloride‐containing solutions. The results of this study show that the formation of Al‐rich ternary phases improved the corrosion resistance of the three‐dimensional‐printed Ti–AlN after quenching. [ABSTRACT FROM AUTHOR]

This paper describes the development and characterisation of bainitic steel for rail applications based on carbide-free, low-alloy steel. The results show that after rolling and subsequently cooling, the designed carbide-free bainitic steel exhibits better mechanical performance than standard pearlitic steel. This is because of its fine, carbide-free bainitic microstructure, which consists of bainitic ferrite and retained austenite laths. Microstructural and mechanical property analysis was carried out using scanning and transmission electron microscopy, X-ray diffraction, hardness measurements, tensile and low-cycle fatigue tests. The obtained results demonstrate that during low cyclic deformation, a partial transformation of the retained austenite into deformed martensite α′ takes place, and strain-induced martensitic transformation occurs. The initial strengthening of the material during low-cycle fatigue was caused by the transformation of austenite into martensite and the increase in the dislocation density of the steel. In addition, an optimal amount of retained austenite in the form of thin layers and islands (dimensions not exceeding 1 µm) made it possible to obtain a high yield while maintaining the high plasticity of the steel. These microstructural features also contributed to the high crack resistance of the tested carbide-free bainitic steel. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels are crucial structural materials for oil field equipment, ship power system and pressurized-water reactor nuclear-power plant applications. However, they are susceptible to intergranular corrosion, stress corrosion, cracking, and corrosion fatigue, especially at high temperatures when the stress corrosion resistance is inferior. Their properties can be improved with the addition of nano reinforcers as in oxide dispersed-strengthened (ODS) steels, i.e., Y2O3 nanoparticles, which enhances the high-temperature mechanical strength and radiation resistance. ODS steels are mostly produced through powder metallurgy (PM) involving mechanical alloying (MA) in a high-energy ball mill followed by sintering methods as spark plasma sintering (SPS) or pulse plasma sintering (PPS). This study aim was to analyze the corrosive behavior of the austenitic 316L stainless steel with the addition of 1 wt. % Y2O3 in two different sizes. The materials were mechanically alloyed from prepared powders in argon atmosphere under various conditions: during 50 h (MA1), 10 h (MA2) and 5 h (MA5) at 250 RPM with 15+15 min break interval and rotation. Test specimens were subjected to salt spray testing in accordance with EN ISO 9227:2017 Corrosion tests in artificial atmospheres - salt spray tests. Afterwards, the surface degradation was analyzed and deeply examined using surface sensitive techniques (FIB/SEM/EDS, optical profilometer), also the samples loss mass was calculated. The obtained results showed that among studied materials, sample sintered from powder milled during 5 hours with smaller size of Y2O3 addition developed greater corrosion resistance. [ABSTRACT FROM AUTHOR]

Nowadays, nuclear energy is one of the most replaceable energy sources for a broader range of advantages [1]. Harsh service conditions are the main concern for the development of structural materials in nuclear applications [2]. The oxide dispersion strengthened (ODS) steel is the most promising candidate for fulfilling the desired criteria as structural materials for nuclear applications [3]. The present study uniquely revealed the newly formed microstructure of ODS steel fabricated by pulse plasma sintering (PPS) to establish the ability to work in extremely severe service conditions. The attempt to fabricate ODS steel by PPS could be the most commendable method over other conventional sintering methodologies. In this research, we produced austenitic ODS steels with Y2O3 addition. The ODS steel powders were produced using different mechanical alloying parameters: duration of 5, 10 and 50 hours of milling at 250 rpm in Ar atmosphere. The influence of 1 wt.% of Y2O3 on the fabrication of ODS steel by PPS has been investigated in terms of microstructure, mechanical properties and corrosion resistivity. Microstructure has been evaluated by SEM, EDS, XRD, TEM and EBSD, mechanical tests were made using an uniaxial tensile test and microhardness, while corrosion resistance was evaluated based on electrochemical tests The microstructural study revealed that the properties of the produced materials depends on the mechanical alloying conditions. The highest tensile strength was achieved after mechanical alloying during 50 h, while the lowest after 5 h of mechanical alloying. The highest elongation was measured after 5 hours of powder milling. It may be supposed that a fine and uniform distribution of oxide particles helps to resist corrosion in ODS steel as compared to coarse grains formed after shorter milling times. [ABSTRACT FROM AUTHOR]

Two model aluminium-magnesium alloys, containing 3 and 7.5 wt.% of Mg, were subjected to plastic deformation by means of hydrostatic extrusion (HE). Two degrees of deformation were imposed by two subsequent reductions of the diameter. Microstructural analysis and tensile tests of the materials in the initial state and after deformation were performed. For both materials, HE extrusion resulted in the deformation of the microstructure—formation of the un-equilibrium grain boundaries and partition of the grains. What is more, HE resulted in a significant increase of tensile strength and decrease of the elongation, mostly after the first degree of deformation. [ABSTRACT FROM AUTHOR]

In this study, the microstructure and corrosion resistance of the as-extruded and as-extruded with subsequent heat treatment Mg-3Al-1Zn-15Li (LAZ1531) alloys have been investigated. The alloys' microstructures consisted of α(Mg), β(Li), Θ-MgLi2Al and Mg17Al12. As a result of annealing, the β(Li) to α(Mg) transformation occurred, and the recrystallization supported the reformation of the Mg17Al12. The electrochemical tests showed that the increased amount of α(Mg) and higher amount of Mg17Al12 in the heat-treated alloy favored reactions and determined it as having better corrosion resistance in 3.5 wt.% NaCl. [ABSTRACT FROM AUTHOR]

In this work, the influence of various volume fractions of the crystalline phase in an amorphous matrix of Mg67Zn29Ca4 alloys was investigated for its corrosion resistance for biodegradable applications. An amorphous Mg67Zn29Ca4 alloy was successfully fabricated using melt casting into a copper mould. Then, to obtain different ratios of the crystalline phase in an amorphous matrix, the obtained amorphous rods with 3 mm diameters were annealed at 190, 230, 250, and 400°C. The volume fraction of the crystalline phase was measured by X-ray diffraction, and the microstructures of the obtained alloys were determined based on scanning electron microscopy images. Electrochemical testing was conducted in simulated body fluid at 37°C. This report shows that the ratio of the volume fractions of amorphous and crystalline phases in alloy microstructures strongly influences their corrosion behaviours. The alloy with a fully amorphous structure was the most resistive in the analysed media. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the structure and corrosion resistance of amorphous, amorphous‐crystalline, and crystalline Mg67Zn29Ca4 alloy for biodegradable applications. This paper presents a preparation method and results of the structural characterization and corrosion resistance analysis of the material. Samples were prepared in the form of 3 mm diameter rods. The structure of the alloy was examined with the use of X‐ray diffractometry and scanning electron microscopy. The thermal properties of the samples were examined with differential scanning calorimetry (DSC). Results of DSC analysis were used to determine heat treatment temperatures, allowing to obtain different fractures of crystalline phase in the material. Corrosion resistance of heat‐treated samples was investigated by immersion tests and electrochemical measurements performed in the simulated body fluid. The X‐ray diffraction results confirmed that the prepared Mg67Zn29Ca4 alloy's structure is fully amorphous. After heat treatment, samples with different fractions of amorphous phase in the structure were obtained. Immersion tests of the samples showed that the structure significantly influenced corrosion resistance in examined materials. It should be pointed out, that certain amounts of crystalline phase in amorphous matrix can greatly improve the corrosion resistance of Mg67Zn29Ca4 alloy. [ABSTRACT FROM AUTHOR]

The results obtained in the present study demonstrate the effects of various types of heat treatment processes on the microstructure and hardness of new trip-assisted carbide-free bainitic steel. The steel was subjected to three variants of heat treatment processing with an isothermal bainitic transformation temperature in a range from 350 to 480 °C. Changes of temperature and time of isothermal holding caused changes in the values of retained austenite (RA) volume fraction and carbon content. Reduction in the isothermal holding temperature resulted in the increased concentration of carbon in austenite. Also, the investigations of the microstructure showed that size and morphology of the austenite evolved during heat treatment. The SEM observations revealed that the steel subjected to heat treatment is composed of the carbide-free bainite with ferrite plates and a high volume fraction of retained austenite in the form of thin layers or islands. With the lower isothermal holding temperature and the higher degree of bainitic transformation, the more the RA morphology changed from island to layer type. The application of the lowest isothermal temperature resulted in a significant refinement of the microstructure components: the bainitic ferrite plates and the RA layers. Also, the mechanical properties obtained from the tensile testing and hardness measurements were correlated to the microstructure of the investigated steel after different isothermal holdings. [ABSTRACT FROM AUTHOR]

The influence of grain boundaries and fine precipitation on the corrosion behavior was investigated in two model aluminum-lithium alloys, namely (in wt%) Al-1.6Li (lithium in a solid solution) and Al-2.3Li (lithium in the form of AlLi precipitation), subjected to three different severe plastic deformation (SPD) treatments which refined the microstructure of the alloys to the ultrafine grain size. The SPD techniques used in the experiments were equal channel angular pressing (ECAP), hydrostatic extrusion (HE), and extrusion-torsion (ET). The corrosion behavior was examined using a potentiodynamic polarization test, electrochemical impedance spectroscopy, and an immersion test followed by a SEM surface analysis. The electrochemical tests were conducted in a 0.1 M NaSO solution added with 100 ppm of Cl. The immersion tests (48 h) were performed in a 3.5% NaCl solution at room temperature. The results indicate that the pitting potential, pit number, and stability of the passive layer formed on the surface of the substrates undergo changes depending on the average grain size and the presence of precipitation or its lack. The corrosion resistance, examined in the solution mentioned above, appears to increase with decreasing average grain size. The ET method gave the microstructure with the lowest corrosion resistance. [ABSTRACT FROM AUTHOR]

This article presents the results of research on the use of modern nondestructive methods such as 3D scanning, thermography and computed tomography (CT) to assess the quality of multilayer ceramic molds. Tests were performed on spherical samples of multilayer ceramic molds in the raw state. Samples were made of molding sands composed of quartz and molochite powders, the alcoholic binder hydrolyzed ethyl silicate (ZKE) and an aqueous binder based on colloidal silica. Thickness measurements of spherical forms were made using a 3D scanner. Porosity measurements were made using CT. Additionally, thermography observations of the mold cooling process were made with controlled temperature and humidity. The results of temperature measurements of samples were compared with measurements of thickness and porosity. The practical goal was to determine the possibility of using thermography, 3D scanning and CT as a quick method for detecting mold defects by varying their thickness, porosity and cracks and for final verification of the ceramic molds' condition before casting. [ABSTRACT FROM AUTHOR]

In this work, the influence of bending an AA5457 alloy sheet and the resulting microstructural changes on its corrosion behavior was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to perform detailed microstructural analyses of the alloy in its original form and after bending. After immersion in naturally-aged NaCl under open-circuit conditions (0.5 M, adjusted to 3 by HCl), post-corrosion observations were made, and electrochemical polarization measurements were performed to investigate the corrosion mechanisms occurring on both surfaces. The results showed that the corrosion of AA5457 is a complex process that mainly involves trenching around coarse Si-rich particles, crystallographically-grown large pits, and the formation of multiple tiny pits around Si-rich nanoparticles. The experimental data showed that bending AA5457 changed the shape and distribution of Si-rich coarse particles, cumulated a higher dislocation density in the material, especially around Si-rich nanoparticles, and all of these factors caused that corrosion behavior of the AA5754 in the bending area was lowered. [ABSTRACT FROM AUTHOR]