In this work, the results of the examinations of the effect of the mold material and mold technology on the microstructure and properties of the casts parts of ductile cast iron have been presented. Four different self-hardening molding sands based on fresh silica sand from Grudzen Las, with organic binders (no-bake process), were used to prepare molds for tested castings. A novelty is the use of molding sand with a two-component binder: furfuryl resin-polycaprolactone PCL biomaterial. The molds were poured with ductile iron according to standard PN-EN 1563:2018-10. The microstructure of the experimental castings was examined on metallographic cross-sections with PN-EN ISO 945-1:2019-09 standard. Observations were made in the area at the casting/mold boundary and in a zone approximately 10 mm from the surface of the casting with a light microscope. The tensile test at room temperature was conducted according to standard PN-EN ISO 6892-1:2016-09. Circular cross-section test pieces, machined from samples taken from castings, were used. In the present experiment, it was stated that interactions between the mold material of different compositions and liquid cast iron at the stage of casting solidification led to some evolution of casting's microstructure in the superficial layer, such as a pearlite rim observed for acidic mold sand, a ferritic rim for alkaline sand, and graphite spheroids degeneration, especially spectacular for the acidic mold with polycaprolactone (PCL) addition. These microstructural effects may point to the interference of the direct chemical interactions between liquid alloy and the components released from the mold sand, such as sulfur and oxygen. Particularly noteworthy is the observation that the use of molding sand with furfuryl resin with the addition of biodegradable PCL material does not lead to an unfavorable modification of the mechanical properties in the casting. The samples taken from Casting No. 2, made on the acidic molding sand with the participation of biodegradable material, had an average strength of 672 MPa, the highest average strength UTS-among all tested molding sands. However, the elongation after fracture was 48% lower compared to the reference samples from Casting No. 1 from the sand without the addition of PCL.

ABSTRACT This work aimed to evaluate the effect of a long-term pre-oxidation process in the air (5000 hours at 650 °C) on the steam oxidation resistance of Cr-rich steels with around 18 wt.% Cr (Super 304H) and around 25 wt.% Cr (HR3C) content exposed for the additional 5000 hours at 650 °C. The effect showed a high impact of a long-term pre-oxidation process and a high content of Cr in the metal matrix of the exposed steels. The steel with a lower Cr content showed spallation of the oxide scale under the oxidation process in the air, and only the steel with 25 wt.% Cr showed no spallation of the oxide scale in both conditions: air and steam. The post-exposure analysis in this work was carried out using Scanning Electron Microscopy (SEM) supported by Energy Dispersive X-ray Spectroscopy (EDS) using an X-Ray mapping function. Phase analysis was performed using an XRD diffractometer.

This paper deals with the issue of using moulding sands with a new two-component binder: furfuryl-resole resin – PCL polycaprolactone for the production of ductile iron heavy castings. The previous laboratory studies showed the possibility of using biodegradable materials as binders or parts of binders’ compositions for foundry moulding and core sands. The research proved that addition of new biodegradable PCL in the amount of 5% to the furfuryl-resole resin does not cause significant changes in moulding sand’s properties. The article presents research related to the production of ductile iron castings with the use of moulds with a modified composition, i.e. sands with furfuryl resole resin with and without PCL. Mechanical properties and microstructure of the casting surface layer at the metal/ mould interface are presented. The obtained test results indicate that the use of a biodegradable additive for making foundry moulds from moulding sand with a two-component binder does not deteriorate the properties of ductile iron castings.

In this work, results of an investigation of the microstructure evolution in Haynes® 230® alloy are presented. The morphological and chemical compositions of the chosen microstructure’s constituents, such as the primary and secondary carbides, were analyzed based on tests in the temperature range 700–800 °C for 1000–3000 h. The prediction of phase evolution within the microstructure was proposed based on the analysis of mutual replacement of carbide-forming elements at the carbide/matrix interface. Based on the results, some complementary markers were considered to describe Haynes® 230® microstructure evolution. Qualitative markers, i.e., defined morphological features, were related to the shape and distribution of microstructure constituents. The study also used quantitative markers related to the local chemical compositions of carbide particles, determined as the ratio of the concentrations of carbide-forming elements Crc/Wc, Crc/CrM and Wc/WM. Microstructure maps created on the basis of these complementary markers for the successive annealing stages reflected the course of its morphological evolution.

Abstract This paper presents the results of research on material and microstructural effects in a hypoutectic Al–Mg– Si–Mn–Fe alloy, modified by the addition of Ti and Ti + P, in two series of castings, gravity and pressure. It has been found that the use of high pressure die casting technology allows for significant improvement of mechanical properties, especially tensile strength and plasticity of the examined alloy. On the other hand, the addition of Ti and Ti + P caused different material effects. In gravity castings, the addition of Ti and Ti + P caused a decrease in strength and plasticity, while in high-pressure castings, an increase in the values of these parameters was observed. The microstructural effects related to the foundry technology and those caused by Ti and P additions were revealed, such as differences in the phase composition of the interdendritic eutectics and in the morphology and dispersion of their phase constituents: Mg2Si and α-Al(Fe,Mn)Si.

This work details the results of the application of the deep learning approach to recognizing the morphological forms specific for particular phase constituents of alloy microstructure visible on microscope images. The elaborated procedure of the Neural Network Learning on this stage of the examinations gives an acceptable effectiveness of recognition of several morphological categories as sphere, polyhedron, petal, needle, ch. script, twig, dendrite based on recorded sets of microscope images of microstructure of chosen cast Al and Fe alloys. The main advantage of the Deep Learning approach presented in this work is the opportunity of its application to any collection of microscope images according to chosen defined classes. Simultaneously, the problems of using fuzzy logic to discriminate very similar objects can be avoided (as twigs and ch. script). Thus, the deep learning approach presented in this paper is a new and perspective tool for analyzing and discovering the knowledge contained in microscopic images of the polyphase alloy microstructure.

This work was focused on two particular phenomena contributing to a damage process of nodular cast iron under tensile stress: Internal destruction of graphite nodule and debonding at graphite/matrix (G-M) interface. The G-M debonding was analyzed depending on the phase characteristics of the metal matrix and with the increase in the distance of the observation field from the main crack surface. Typical morphological effects of decohesion in the graphite-matrix microregions related to an internal structure of graphite nodule were revealed and classified. The obtained results of the microscopic observations suggest that the path of both types of internal cracks in the graphite nodule passed through areas of weakened cohesion. Detailed microscopic observations allowed revealing some additional phenomena associated with G-M debonding along the G/M interface. In the most ductile of the tested alloys, with ferritic and ausferritic matrix, the G-M debonding was preceded by the formation of a layer of shifted graphene plates in the external envelope of the spheroid. In the alloys of polyphase pearlitic and ausferritic matrix, the revealed morphology of the G-M interface suggests that G-M debonding might be delayed by the interaction with some phase components as cementite lamellae and austenite plates.

In this work, the observations of the fracture surface after standard tensile tests of several kinds of spheroidal cast irons, ferritic and austempered ductile irons, have been carried out by means of scanning electron microscopy. The local crack path in the area of graphite (G)/matrix (M) interface has been analyzed as affected by a matrix phase composition and the austempering treatment parameters. The obtained results allowed identifying some determination factors for debonding mode at the G/M interface and their role in a final damage mechanism. Some microstructural details in the microregions composed of graphite and matrix showed that the G-M debonding mode in the separation area of the G/M interface seems to be controlled by macroscopic properties of the alloy and by the morphology of G/M interface. On the other hand, the internal destruction of graphite nodule has been mainly determined by a structure and anisotropy of graphite crystal lattice.

In this paper, the effect of applied multi-variant heat treatment on microstructure, phase composition and mechanical response of Haynes 282 nickel-based superalloy was investigated. For this reason, temperatures of both stages of standard two-stage aging treatment (i.e., 1010 °C/2 h + 780 °C/8 h) were extended to 900-1100 °C/2 h and 680-880 °C/8 h ranges, respectively. Consequently, 30 different variants of heat treatment were applied. The microstructural features of heat-treated samples were investigated by means of light microscopy and SEM/EDS methods, while mechanical properties were examined via microhardness measurements. It was found that by using various combinations of temperatures of the first and second stage of aging, the room temperature hardness of Haynes 282 alloy can be decreased by ~ 100 HV units or increased by up to 25 HV units as compared to that of the alloy subjected to the standard heat treatment schedule. The mechanical response of the alloy is determined by a complex structural evolution involving the secondary precipitation of γ′, M23C6 and M6C phases, as well as their interaction with the fcc γ matrix.

Aim of the study is the adaptation of a modeling concept to internal oxidation during steam oxidation using the cellular automata (CA) approach. The CA system is implemented for the alloys that undergo most severe corrosion degradation. In this work, steam oxidation process for two solid‐solution strengthened alloys; Haynes® 230®, 617 alloy, two γ’‐strengthened alloys; 263 and Haynes® 282®, and three austenitic steels rich in Cr: 309S, 310S, and HR3C, are analyzed. The study shows that the exposure in steam environment leads to a thin oxide scale formation consisting mainly Cr2O3 and MnCr2O4 spinel type oxide, except alloy 617, where NiCr2O4 spinel is observed. The modeling studies of internal oxidation development are applied to γ’‐strengthened alloys, Haynes® 282® and alloy 263, and are shown to be in good agreement with the experimentally observed pronounced internal oxidation attack.

The polyphase eutectics (α-Al+intermetallic+Si) constituting the final aluminum alloy microstructure were characterized by their phase composition, growth mechanism, and morphology of eutectic crystals. The main groups of eutectic phase constituents were presented with a special attention paid to intermetallic phases. Morphology of different types of polyphase eutectics, among those divorced, was characterized and presented (as microscopic images) on microphotographs. The microstructural effects of stable and metastable phases competition in the stage of nucleation and growth of polyphase eutectics as affected by local cooling rate and liquid alloy composition were described. Some examples of the evolution of the phase composition of eutectics in commercial alloys due to modifications of technological procedures were presented.

The aim of the work was to investigate corrosion resistance of highly alloyed steels and Ni-based alloys in a steam atmosphere for 1000 h at 700 °C. In these steam oxidation experiments, two solid solution strengthened alloys; Haynes ® 230 ® , 617 alloy, two gamma-prime ( γ ′) strengthened alloys; 263 and Haynes ® 282 ® and three Cr+Ni- rich stainless steels: 309S, 310S and HR3C austenitic steels were exposed. The study showed that the materials exposed commonly developed thin oxide scales; in Ni-based alloys, these consisted of mainly MnCr 2 O 4 spinels and Cr 2 O 3 , with the exception of 617 alloy where NiCr 2 O 4 spinels and Cr 2 O 3 were found. In Fe-based alloys, Cr 2 O 3 , MnCr 2 O 4 spinels, Fe,Mn(SiO) 4 , and finally Fe 3 O 4 developed. No evaporation of chromia has been found within 1000 h test period. Furthermore, the development of TiO 2 was not observed into a large extent in Haynes ® 282 ® and 263 alloy, in contrast to the study performed at 800 °C under the same steam environment conditions.

The aim of the study was to design and optimize the complex, two-step heat treatment of Cu–Ni (Mn, Mo) ductile iron. A method for the formation and investigation of austempered ductile iron (ADI) by means of complex two-step and as comparative, standard one-step heat treatments has been developed, using quenching dilatometer. Investigations of proceeding phase transformations using differential dilatometric and DSC analysis supported by microstructural observations, hardness and austenite volume measurements have been carried out. An analysis of the temperature sequence of the ausferrite decomposition in the one-step and two-step ADI was performed, which allowed for the separation and identification of the effects responsible for the carbon-enriched austenite decomposition. A quantitative relationship was established between basic dimensional effects revealed on the differential dilatometric curve of ausferrite decomposition, which enables prognosis and optimization of the parameters of complex ADI heat treatment variants. Verification tests were performed on a stand equipped with salt furnaces enabling a quick transfer of samples from one bath to another without changing their initial temperature. Optimization of the two-step ADI heat treatment with the use of quantitative dilatometric analysis of the ausferrite decomposition, allowed to obtain for the temperature step-down heat treatment 390 °C/15, 20 min ≫ 270 °C/130 min the excellent mechanical properties, unattainable by means of standard 1-step ADI heat treatment.

A procedure a for multi-step characterization of microstructural features observed in austempered ductile cast iron (ADI), was proposed based on the results of microscopic examinations, a local X-ray microanalysis and EBSD-based crystallographic evaluation. The polyphase complex microregions having an increased content of alloying elements such as Mo, Cr, Mn in comparison with that estimated for the alloy's matrix, were observed in the examined material. As a first step, a classification of microregions was performed based on their morphology and specific distribution in the alloy's microstructure. Subsequently, by using established criteria for the selection of microanalysis data for a further microregions discrimination, several groups of particles characterized by a particular ratio of the alloying elements, were distinguished. The particles were classified based on the specific range of the carbide stabilizers concentration revealed, then were ascribed in situ to two types of carbides identified by means of EBSD analysis. Furthermore, the effect of heat treatment conditions on the evolution of the chemical composition of the microregions was examined experimentally and discussed.

The objective of this study was to analyse an innovative, cyclic heat treatment used to obtain austempered ductile iron (ADI) in laboratory conditions by means of quenching dilatometer. The relationship between the physical properties of ADI - hardness HV30 and fraction of carbon-enriched austenite V-a, considered as parameters forecasting the mechanical properties of ADI - tensile strength R-m and elongation A, was compared with the relationship between two basic dimensional effects revealed in differential dilatometric curves of ausferrite decomposition. The mutual compatibility between these relationships was established. Heat treatment optimization method based on the analysis of differential dilatometric curves of the ausferrite decomposition has been developed. The both approaches enabled selection of the optimal parameters of cyclic austempering and prediction of the mechanical properties which were unattainable by means of standard one-step ADI heat treatment. A kinetic analysis of decomposition after 1-step and cyclic ADI heat treatments was performed. The activation energy values for decomposition of ausferrite obtained by cyclic heat treatment 270 degrees C boolean AND boolean OR 390 degrees C and 270 degrees C boolean AND boolean OR 350 degrees C - 156 and 181 kJ/mol, respectively were found. The comparison with the activation energy for decomposition of ausferrite obtained by standard, 1-step heat treatment - 249 kJ/mol (270 degrees C), 230 kJ/mol (310 degrees C), 174 kJ/mol (350 degrees C) and 170 kJ/mol (390 degrees C) indicates that the cyclic heat treatment does not improve thermal stability of ausferrite.

The strength of Al-Mg-Si-Mn casting alloy strongly depends on Mg content in solid solution and precipitation of strengthening phases. Alloys with the nominal composition AlMg5Si2Mn with addition of Li and Ti+Zr were studied by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and energy dispersive X-Ray analysis (EDX). DSC measurements show that the eutectic melting temperature was about 595°C and it is higher than that of commercial A356 casting alloy. The macro- and microhardness tests show that in as-cast state hardness were higher than for A356 and continuously growth during artificial aging. TEM investigations reveal that during artificial aging three different precipitation types are forms in the alloy matrix. Two of them belong to the different structures of Mg2Si precipitates. Appearance of the third one identified as d’-Al3Li phase represent that Al-Mg-Si system can be successfully used for designing of Li-containing casting alloy which is not developed yet.

In this paper the results of the microscopic observations of the intermetallic AlFeMnSi phases crystals formed in the liquid hypo- and eutectic AlSi alloys containing transition metals 3.0 wt.% Fe and 0.1, 0.5 and 2.0 wt.% Mn were presented. The crystals morphology has been revealed on both polished and deep etched microsections. The different stages of the primary AlFeMnSi phases particles formation in the solidifying alloy and their final morphology were shown as influenced by cooling rate and alloy chemical composition.

The structure of permanent mold and high pressure die castings of the AlMg5Si2Mn alloy after alloying with Li and Sc has been investigated by scanning and transmission electron microscopy, hardness and microhardness measurements, energy dispersive X-ray analysis. Three conditions, as cast, solution treated and aged, were investigated. It was shown that in as-cast state, the structure of an alloy having the nominal composition AlMg5Si2Mn consists of four phases: first – the Al based solid solution, second – the (Al)+(Mg2Si) eutectic, third – the primary Mg2Si crystals and fourth – the a-Al(Mn, Fe)Si phase. Similar phases were observed in the alloys containing Sc or Li. After two days of storing in an as-cast condition, the solid solution in all tested alloys decomposesand forms zebra-crossing shaped precipitates. TEM examinations revealed that these precipitates nucleate heterogeneously on dislocations. The solution treatment at 575.0°C results in spheroidization of the Mg2Si lamellas, dissolution of the precipitates and formation of a-Al(Mn, Fe)Si dispersoids, nucleating on the surfaces of Mg2Si lamellas. In the Sc containing alloys, the formation of Al3Sc was detected after 120 min soaking. Further heating resulted in the growth of these precipitates. Aging of the Al-Mg-Si alloys leads to an increase of hardness in all studied alloys. This effect is mainly related to precipitation strengthening, via solid solution decomposition and formation of b’’-phase. In Li-alloyed specimens, plates of b Mg2Si phase were observed together with small cubic-shaped d’ Al3Li precipitates. The structure of permanent mould and high pressure die castings of the AlMg5Si2Mn alloy after alloying with Li and Sc has been investigated by scanning and transmission electron microscopy, hardness and microhardness measurements, energy dispersive X-ray analysis. Three conditions, as cast, solution treated and aged, were investigated. It was shown that in as-cast state, the structure of an alloy having the nominal composition AlMg5Si2Mn consists of four phases: first - the Al based solid solution, second - the (Al)+(Mg2Si) eutectic, third - the primary Mg2Si crystals and fourth – the phase. Similar phases were observed in the alloys containing Sc or Li. After two days of storing in an as-cast condition, the solid solution in all tested alloys decomposes and forms zebra-crossing shaped precipitates. TEM examinations revealed that these precipitates nucleate heterogeneously on dislocations. The solution treatment at 575.0°C results in spheroidization of the eutectic, dissolution of the precipitates and formation of dispersoids, nucleating on the surfaces of Mg2Si lamellas. In the Sc containing alloys, the formation of Al3Sc was detected after 120 min soaking. Further heating resulted in the growth of these precipitates. Aging of the Al-Mg-Si alloys leads to an increase of hardness in all studied alloys. This effect is mainly related to precipitation strengthening, via solid solution decomposition and formation of b²-phase. In Li-alloyed specimens, plates of b Mg2Si phase were observed together with small cubic-shaped d¢ Al3Li precipitates.

The paper presents the results of thermophysical properties of selected vermicular graphite cast iron with nominal chemical composition of 3.70 C; 2.30 Si; 0.44 Mn; 0.054 P; 0.015 S; 0.017 Mg (wt. %). The comparative studies of the alloy were performed using differential scanning calorimetry, dilatometry and laser flash analysis. The calorimetric investigations proved that upon the heating to melting temperature (~1200°C), four endothermic transformations take place: 1) ferromagnetic → paramagnetic at 742°C, 2) pearlite → austenite at 824.2°C, 3) allotropic transformation of bcc ferrite to fcc austenite at 802°C, 4) melting at 1173.1°C. The character of the dilatometric curve shows small deviation at the temperature above 810°C corresponding to the pearlite → austenite transformation. The values of thermal diffusivity and thermal conductivity change throughout the entire examined temperature range. Both curves showed a changeover from negative to positive trends between 700 and 800°C. This effect might be associated with the pearlite → austenite transformation.