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This document is a special issue of the journal "Materials" that focuses on the recent progress in the structure transition, processing, characterization, and applications of metallic materials. The issue includes research papers on various topics such as the development of dispersion-strengthened copper alloys, the characterization of carbide precipitation in steel, the effect of magnetic fields on aluminum bronze, and the enhancement of impact toughness in cast iron through heat treatment. The issue aims to provide comprehensive and up-to-date information for researchers, engineers, and industry experts in the field of metallic materials. [Extracted from the article]

This paper presents the results of research conducted in the field of the technology of surface hardening of castings from unalloyed and low-alloy nodular cast iron using the laser remelting method. The range of studies included macro- and microhardness measurements using Rockwell and Vickers methods as well as metallographic microscopic examinations using a scanning electron microscope. Moreover, abrasive wear resistance tests were performed using the pin-on-disk method in the friction pair of nodular cast iron—SiC abrasive paper and the reciprocating method in the friction pair of nodular cast iron—unalloyed steel. Analysis of the test results shows that the casting surface layer remelting by laser for unalloyed nodular cast iron results in a greater improvement in its resistance to abrasive wear in the metal–mineral system, as compared to low-alloy cast iron. Additionally, carrying out the laser hardening treatment of the surface layer made of the tested grades of nodular cast iron is justified only if the tribological system of the cooperating working parts and allowable dimensional changes during their operation are known. [ABSTRACT FROM AUTHOR]

The paper provides a discussion on the results of studies of the effect exerted by combined degradation factors typical of four types of wear: abrasion, impact–abrasion, tribocorrosion, and impact–abrasion–corrosion, conducted for chain wheels made of Ni-Cu alloyed austempered ductile iron. The studies consisted of determining the content of retained austenite in the structure of the cast irons in question, establishing the measures of wear following wear testing, and identifying the basic surface degradation mechanisms observed in the chain wheels tested following multifactorial wear processes. The chain wheels made of ADI were found to have sustained the greatest damage under the impact–abrasion–corrosion (three-factor) wear scenario, while the wear was least advanced in the abrasion (one-factor) wear case. Another observation derived from the studies is that the combined effect of dynamic forces, corrosion, and quartz sand-based abrasives causes increased surface degradation in the cast iron grades taken into consideration compared to processes characterised by a reduced number of degradation factors (i.e., one- or two-factor wear processes). Additional hardness tests and XRD analyses revealed that a distinctive effect attributable to combined degradation factors on the surface hardness increased value and implied that bench testing was followed by phase transition. [ABSTRACT FROM AUTHOR]

The preparation process and composition design of heavy-section ductile iron are the key factors affecting its fracture toughness. These factors are challenging to address due to the long casting cycle, high cost and complex influencing factors of this type of iron. In this paper, 18 cubic physical simulation test blocks with 400 mm wall thickness were prepared by adjusting the C, Si and Mn contents in heavy-section ductile iron using a homemade physical simulation casting system. Four locations with different cooling rates were selected for each specimen, and 72 specimens with different compositions and cooling times of the heavy-section ductile iron were prepared. Six machine learning-based heavy-section ductile iron fracture toughness predictive models were constructed based on measured data with the C content, Si content, Mn content and cooling rate as input data and the fracture toughness as the output data. The experimental results showed that the constructed bagging model has high accuracy in predicting the fracture toughness of heavy-section ductile iron, with a coefficient of coefficient (R2) of 0.9990 and a root mean square error (RMSE) of 0.2373. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis of ausferritic ductile cast iron matrix obtained through heat treatment and in its raw state. Ausferrite without heat treatment was achieved by modifying the chemical composition, while nodular graphite was produced using Inmold technology. The presence of compacted graphite in the as-cast ausferritic cast iron was attributed to elements that impede the crystallization of nodular graphite. This study demonstrates that an ausferritic matrix in ductile cast iron can be achieved by incorporating molybdenum in conjunction with nickel or copper. Thermal and derivative analysis (TDA) revealed a minor thermal effect during the transformation of austenite into bainitic ferrite in as-cast ausferritic cast iron. Furthermore, the transformation of austenite in cast iron containing nickel was observed to occur at a temperature of approximately 60 °C higher than in cast iron with copper. The structure of bainitic ferrite platelets in as-cast ausferritic ductile cast iron resembled that of Austempered Ductile Iron (ADI). It was revealed that the amount of austenite in as-cast ausferritic ductile cast iron is more than double that in ADI. The carbon content of austenite was estimated theoretically, revealing that alloying additives in the as-cast ausferritic ductile cast iron reduce the solubility of carbon in austenite, thereby significantly influencing the properties of the cast iron. [ABSTRACT FROM AUTHOR]

This paper deals with the austempering of ductile iron (ADI) and clarifies the influential austempering parameters during the production of ADI. During the austempering process, the heat treatment parameters can be varied, thus influencing the final microstructure and, of course, the mechanical properties of ADI. To appropriately conduct experiments and obtain good results, an experimental plan was developed using the Design Expert 13 software. Along with the heat treatment parameters, the influence of the copper content on the ADI toughness, tensile strength, and elongation was determined. The obtained results from this experiment were used to develop unique mathematical models which describe the influences of heat treatment and copper content on the observed mechanical properties of ADI samples. These mathematical models can be applied to predict the analysed mechanical properties of ADI in the dependence of heat treatment parameters and copper content in base ductile iron. For the multi response optimisation of toughness, tensile strength, and elongation, a hybrid grey-fuzzy technique was presented as a significant contribution to the enhancement of the analysed mechanical properties. Consequently, the copper content and heat treatment parameter levels that resulted in the maximal mechanical properties' functions were defined. [ABSTRACT FROM AUTHOR]

The production of high-quality castings without foundry defects at minimal production costs is a constant priority for foundries. Innovation and optimization of production processes are key to achieving this goal. Computer simulation of foundry processes offers a modern alternative to expensive and time-consuming experiments in real foundries and provides a reliable representation and analysis of casting and solidification processes. A detailed analysis of the casting and solidification simulation results allows the prediction of various risks that can cause defects in cast castings, thereby reducing their quality and, last but not least, the cost of their production. This paper deals with the analysis of a computer simulation of the casting of a brake disc in a Slovak foundry. This brake disc has had shrinkages and micro shrinkages that reduce the internal quality of the casting. These defects occurred in the ribs in the upper part of the casting under the feeders. A computer simulation of the casting and solidification of this casting was made according to the real conditions. It turned out that the designed gating system with a system of feeders was not sufficient to eliminate the emerging defects. A new layout for the feeders was proposed, which ultimately eliminated the occurrence of defects based on the results of the computer simulation. The input parameters were set to be as close as possible to the actual needs of the foundry. Moreover, 3D models of the assemblies were designed in SolidWorks Premium 2015 x64 Edition CAD software, and the filling and solidification simulations were performed using the NovaFlow & Solid CV 4.6r42 simulation program. [ABSTRACT FROM AUTHOR]

Purpose: The foundry industry incurs additional costs as a result of defective castings. Shrinkage defects are a frequent problem in ductile iron castings. It is still essential to understand how shrinkage porosity varies in size when the ductile iron composition changes. This information can be used to produce high-quality cast parts and determine the best processing conditions. The objective of this research paper is to examine the effect of carbon equivalent and inoculation on the morphology of the shrinkage defect using thermal analysis. Design/methodology/approach: This study focuses on certain thermal analysis parameters, such as the angle of the first derivative curve at the solidus temperature, recalescence and its relationships to graphite nucleation and shrinkage tendency. The results of thermal analysis in terms of the cooling curve and its derivative parameters, and thorough characterizations of the shrinkage observed in cup castings produced with various melt compositions and inoculation are presented in the current study. Findings: The proportion of caved surfaces and macro shrinkage porosity defects has been reduced as the carbon equivalent of melt increases from hypoeutectic to a hypereutectic composition. The composition that is slightly hypereutectic has the lowest shrinkage propensity. Although inoculation reduces shrinkage, the importance of this parameter differs depending on the carbon equivalent. Originality/value: The percentage of macro shrinkage porosity and the angle that the cooling rate curve forms are strongly correlated. It is found that the macro shrinkage size decreases as the angle of the first derivative curve at the solidus temperature is reduced. Further, lower macroporosity is produced by a metal that has a higher nodule count in association with a greater cooling rate toward the end of the solidification process. [ABSTRACT FROM AUTHOR]

The selection of MgFeSi alloy and inoculants used for ductile iron treatment has confounded members of the foundry industry for many years. Frequently foundries have used certain types of alloys "because they have always done it that way" or "because someone else was doing it." The current study involves ductile iron produced with three grades of MgFeSi with varying levels and types of rare earths along with four different inoculants. The iron was cast into test samples of various thickness from 2×2×8 inches to 10×10×8 inches. Mechanical properties and microstructures were evaluated at multiple locations in each of the 36 samples for a total of 156 points of data. In this paper, we will summarize the findings for differing section sizes. [ABSTRACT FROM AUTHOR]

This paper summarizes the investigation of the conversion of an 11-piece steel fabrication to an austempered ductile iron (ADI) casting. It was a collaborative effort involving the component manufacturer, foundry, machinist, local university, and an ADI heat treater. A number of design concepts were developed, with the final, significantly stronger, ADI design being compared to the fabrication using FEA analysis. The resulting conversion, at similar weight and cost, eliminated the failures that were experienced in the fabricated components in addition to reducing the production lead-time. [ABSTRACT FROM AUTHOR]

The paper deals in depth with characterizing bead-on-plate welds on EN-GJS-500-14 base metal, utilizing two filler metals: a pure Ni wire and a NiFe wire containing 45 wt pct Ni. The welds were conducted using the same heat input to ensure comparability in microstructure analysis. The microstructural observations were carried out using optical and scanning electron microscopies, X-ray tomography, X-ray diffraction analysis, and microhardness testing. Thermodynamic simulations using the non-equilibrium Scheil solidification model provide insights into the solidification process and the underlying metallurgical factors associated with the observed microstructural evolution. The observations revealed that the pure Ni wire deposited a softer fusion zone with graphite precipitation, while cementite precipitated in the fusion zone of NiFe alloy. The formation of martensite structures with different morphologies was the predominant microstructural evolution in the heat-affected zone of both welds. The partially melted zone of the pure Ni weld is narrower than the NiFe weld because more diffusion of Ni avoids widening the brittle structures in the partially melted zone. An unmixed zone in the form of a peninsula was exclusively observed in the fusion zone of the NiFe weld because of inadequate diffusion of Ni into the liquified materials along the fusion boundary. [ABSTRACT FROM AUTHOR]

This article is a tribute to Richard (Rick) Gundlach, a highly accomplished metallurgical engineer who made significant contributions to the metalcasting industry. Rick received numerous awards and honors for his work, including the Joseph S. Seaman Gold Medal and the AFS Award of Scientific Merit. He was also a Fellow of the American Society of Materials. Throughout his career, Rick published over 70 technical papers and held two U.S. patents. His passion for metallurgy, metalcasting, and educating others was evident in his work and will continue to inspire the industry. The article also includes Rick's two final papers, which were submitted on his behalf by his colleague, Dr. John Tartaglia. The papers focus on the effects of silicon in high-Cr white cast irons and achieving higher strength and ductility in heavy-section ductile iron castings. Rick's contributions to the industry will be greatly missed. [Extracted from the article]

In this paper, the pre-oxidation products, surface silicon content, hot-dip galvanized layer structure and corrosion resistance of nodular cast iron pre-oxidized by sodium bicarbonate were studied by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction. When the pre-oxidation temperature is 100 °C, the pre-oxidation product is primarily Fe2O3. The oxidation products are Fe2O3 and SiO2 at 200 °C and that is mainly SiO2 at 300 °C. The surface silicon content of the pre-oxidized samples decreases first and then increases with increasing pre-oxidation temperature. The silicon content of samples after alkali and acid washing decreases with increasing pre-oxidation temperature. With the increase in pre-oxidation temperature, the thickness of the alloy layer in the zinc coating of nodular cast iron continuously decreases. The thickness of the alloy layer in the zinc coating of nodular cast iron pre-oxidized at 300 °C is only 37.3 μm, which is 43.9% lower than that of nodular cast iron without pre-oxidation. [ABSTRACT FROM AUTHOR]

Microstructural characteristics and mechanical properties of the ductile iron in three heat treatment processes (normalizing, quenching + high‐temperature tempering and isothermal quenching) were investigated in this paper. The pearlite and ferrite with large‐sized spherical graphites can be obtained in the normalized sample, and the spherical graphites with relatively large size can still be observed in the mechanical mixture of tempered martensite and acicular ferrite for the quenched‐tempered sample. Meanwhile, the lower bainite accompanied with the relatively fine spherical graphites are existed in the isothermal‐quenched sample. The difference of tensile strength is mainly caused by the phase composition, distribution and size of the spherical graphites and the effect of the solid solution strengthening. The weaker degree of the debonding damage, higher proportion of high‐angle grain boundaries will improve the impact toughness of the ductile iron. In a word, the optimum combination of strength and toughness is acquired by using isothermal quenching, and the tensile strength and impact toughness are ~1350 MPa and ~10.62 J, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the ferrite grain size was controlled by two annealing methods, which can affect the low-temperature toughness of ferrite nodular cast iron. The annealing temperature ranged from 720 to 750 °C, and one annealing method consisted of constant temperature heating with temperature controlled to ± 1 °C. The other method employed cyclic heating, with a temperature change of 19 (+ 14, − 5) °C and a period of 450 s. The change law of ferrite grain size under low temperature annealing and the effect of ferrite grain size on low-temperature impact toughness were studied. The conditions under which the superheated ferrite does not transform into austenite were determined. The mechanism by which coarse ferrite favors high toughness in nodular cast iron at low temperatures was discussed. Nodular cast iron with tensile strength of 392 MPa, yield strength of 206 MPa, elongation of 26% and impact energy of 13.5 J at − 70 °C was obtained. [ABSTRACT FROM AUTHOR]

This work evaluated the machinability characteristics of three different austempered ductile irons using three machinability indicators: cutting force, tool wear, and surface roughness. Additionally, this paper addresses the interplay among the production conditions of ADIs, microstructural development, the TRIP effect arising from transformations of the retained austenite into martensite, and the machinability behavior of ADIs. Various characterization studies including hardness measurement, X-ray diffraction analysis, light and electron microscope were used. Machinability results indicated that the increase in cutting force is always associated with a corresponding increase in the martensite content when the cutting depth was increased from 0.5 to 2.0 mm. Such correlation is more evident with ADI grade austempered at high austempering temperature, 375 °C (ADI-375). It was noticed that although ADI-375 has only 0.46% martensite in the structure before machining, this ratio increases with the highest depth of cut of 2.0 mm to reach about ~ 23% martensite with a corresponding increase in the cutting force. Ferrite content and morphology have a great impact on the overall surface finish of each grade as it leads to deteriorating the surface characteristics of the investigated alloys. This could explain the highest roughness values across all processing experiments obtained in the ADI grade austenitized in the intercritical region (IADI), which mainly contains the highest ferrite content. Tool wear and chip characteristics were also studied in this work. [ABSTRACT FROM AUTHOR]

Spheroidal graphite cast irons (SGCIs) have been commonly used in automotive and energy sectors where superior mechanical strength and wear resistance are required. This paper investigated the performance of the SGCIs under severe wear conditions as a function of Ti content and cooling rate. SGCIs alloyed with various Ti content (0, 0.1, 0.2, 0.3, and 0.5 wt%) were produced by green sand-casting process in different section sizes (10, 30, and 50 mm). Ball-on-disk type wear equipment with an Al 2 O 3 ball was used to determine the wear rates of the SGCI samples. With increasing Ti content, up to 45% of nodular graphite turned into vermicular graphite, depending on the Ti addition and section sizes. Carbide precipitation was observed in the matrix due to the carbide-forming effect of Ti. The hardness and wear resistance of the SGCIs were improved by adding Ti owing to the combined effects of increasing pearlite and TiC particles precipitated in the matrix. Thinner-wall castings provided a faster cooling rate, which improved hardness and wear resistance. Alloying with 0.5 wt% Ti decreased the wear rates up to 35%. • Increasing Ti changed graphite morphology from nodular to vermicular. • Ti addition increased hardness by solid-solution hardening and TiC formation. • Increasing Ti content and cooling rate provided a decrease in wear rates. • Ti-alloyed SGCIs predominantly suffered from abrasion and adhesion. • The highest wear resistance was achieved in 0.5 wt% Ti at 10 mm wall thickness. [ABSTRACT FROM AUTHOR]

Seismic events disrupt the operation of water distribution networks. Proactive seismic rehabilitation decision-making methods are necessary to ensure maximum serviceability after a seismic event. Most recent proactive seismic rehabilitation decision-making models of water distribution networks are sensitive to network hydraulics and pipe fragilities. Although network hydraulics and pipe fragilities are influenced by pipe degradations, the effects of degradation on proactive seismic rehabilitation decision-making have not been studied. The probabilistic nature of the water pipe degradation makes the consideration of degradation challenging. This research aims to investigate the effects of the degradation of pipes on the seismic rehabilitation decision-making of water distribution networks. The methodology includes (1) designing simulation experiments; (2) integrating the effects of inside and outside degradation with seismic rehabilitation decision-making; and (3) conducting statistical analysis to identify the effects of integrating pipe degradation. The simulation experiments were designed to investigate the effects of degradation on the inside surface of pipes and the outside surface of pipes individually and combinedly. A simulated annealing (SA)–based optimization algorithm was used to identify the critical pipes and associated maximum serviceability for each experiment and each budget constraint. To assess the statistical significance of integrating degradation, two statistical tests were performed. The application of the proposed approach was illustrated on a benchmark network. The selected benchmark network consisted of cast iron pipe and ductile iron pipe. Degradation of cast iron pipe was considered in this study. This framework can be used for other materials. This study was based on five rehabilitation constraints with a focus on rehabilitation costs. The optimization algorithm was employed to identify critical pipes corresponding to each rehabilitation constraint. The results for each simulation experiment showed that the identified critical pipes differed. The associated maximum serviceability was reduced for the same budget constraints if outside and inside degradation were considered individually and combinedly. The associated maximum serviceability was reduced by 3%–4% because of the individual effect of outside or inside degradation, and 6%–7% because of the combined effect of inside and outside degradation. The changes in the identified critical pipes and associated maximum serviceability due to the consideration of outside and inside degradation imply the dependency of a proactive seismic rehabilitation decision-making model on outside and inside degradation. The statistical test results imply that the degradation of pipes in the water distribution network has an impact on seismic rehabilitation decision-making models of water distribution networks. Therefore, it is recommended to integrate the degradation effect with existing seismic rehabilitation decision-making models. [ABSTRACT FROM AUTHOR]

Ductile iron (DI) samples were immersed in near-neutral, alkaline sodium hydroxide (NaOH), and sodium chloride (NaCl) environments for 180 days. The influence of microstructure on the corrosion resistance of three DI specimens was investigated. Microstructures, electrochemical measurements, and the characterization of the corroded surfaces were analyzed. The experimental results from this study were used to validate a model generated from hybrid adaptive neuro-fuzzy inferences system-particle swarm optimization (ANFIS-PSO) algorithms. The hybrid ANFIS-PSO modelling technique was improvised for a detailed evaluation of corrosion rate of ductile cast iron materials in different environments. The integrated hybrid ANFIS-PSO model revealed a sharp rise in localized corrosion caused by chloride-induced structural deterioration at the nanoscale for some of the grains. The performance results revealed that the fuzzy c-mean (FCM) clustering outperformed other clustering approach in the neuro-fuzzy model. Accuracy values of 92.9% and 93.7% were recorded for the training phase of ANFIS-FCM and ANFIS-PSO-FCM respectively for corrosion rates. The percentage error of the ANFIS-PSO predictions is significantly lower than the ANFIS-standalone prediction. This shows that the ANFIS-PSO with FCM approach is a better model for predicting corrosion rates. This will contribute to the body of knowledge for ductile iron, corrosion, and corrosion modelling using machine learning. [ABSTRACT FROM AUTHOR]

Cast iron welding improves the performance of joints using welding rods for cast iron. However, such rods are more than twice as expensive as those for mild steel. The authors found that when spheroidal graphite cast iron is melted and rapidly solidified, spherical graphite nodules aggregate and moved to the surface. If the spherical graphite nodules in the fusion zone moved to the surface, the carbon concentration may reduce, thereby suppressing the generation of ledeburite. In this study, by irradiating with YAG laser, I-type butt-welded joints were fabricated using L materials (with an average spherical graphite nodule diameter of 52 µm) specimen without groove width. Ferrite and pearlite matrices joints were undermatch joints. Applying PWHT (Post Weld Heat Treatment) restored the joint strength to more than 90% that of the base metal. The impact value as-welded joint dropped to less than 15% of that for the base metal. However, it could be recovered up to about 40% of that for the base metal by PWHT. Ferrite matrix joints after PWHT exhibited similar level impact values as the as-welded pearlite matrix joints. Moreover, the surface of spheroidal graphite cast iron with different numbers and size of spherical graphite nodules was irradiated with YAG laser. As the result, at irradiation feed rates above 100cm/min L materials specimen exhibited a much lower hardness in the fusion zone than S materials (with an average spherical graphite nodule diameter of 27 µm) specimen. The spherical graphite nodules in the fusion zone moved to the surface during rapid melting by laser irradiation. In the S materials specimen studied, more ledeburite, martensite and retained austenite formed near the fusion boundary than with the L materials specimen. [ABSTRACT FROM AUTHOR]

SiMo ductile cast iron combines ease of part fabrication with good mechanical properties, including a usable plasticity range. Its poor corrosion resistance inherited from grey cast iron could be alleviated through alloying with Al or Cr additions capable of forming a dense oxide scale protecting the substrate. However, the presence of Al and Cr in cast iron tends to make the material brittle, and their optimum alloying additions need to be studied further. The present work was aimed at investigating the effect of crystallization rates on microstructure changes during directional crystallization of SiMo-type alloys with up to 3.5% Al and 2.4% Cr. The experiment was performed using the Bridgman–Stockbarger method. The tubular crucible was transferred from the hot section to cold section at rates ranging from 5 mm/h to 30 mm/h with a 4/5 crucible length and then quenched. The introduced Al promoted graphitization up to a point, wherein, at the highest applied addition, the graphite precipitation preceded crystallization of the rest of the melt. A rising level of Cr in these alloys from 1% to 2.4% resulted in the formation of low and high contents of pearlite, respectively. The higher crystallization rates proved effective in increasing the ferrite content at the expense of pearlite. In the investigated cast iron samples with smaller applied alloying additions, Widmanstätten ferrite or ausferrite, i.e., fine acircular phase, were often found. The switch from directional crystallization to quenching caused a transition from a liquid to solid state, which started with nucleation of islands of fine austenite dendrites with chunky graphite eutectic separating them. As these islands expanded, they pushed alloying additions to their sides, promoting carbide or pearlite formation in these places and forming a super-cell-like structure. The performed experiments helped gather information concerning the sensitivity of the microstructure of SiMo cast iron modified with Al and Cr to crystallization rates prevailing in heavy cast structures. [ABSTRACT FROM AUTHOR]

In this paper, laser cladding technology coated the ductile iron surface with austenitic stainless steel. To improve the wear resistance of the coating, consider a heat treatment way to strengthen it. The effects of temperature and time on microstructure, hardness, and wear resistance of austenitic stainless steel coating were investigated. The results show that the martensitic phase was added to the samples at different times of 950 ℃, and the carbide precipitated phase was the main change in the microstructure. At 1050 ℃, the samples also changed from austenite to martensite at different deal times, and the microstructure mainly changed between dendrites. The hardness and abrasion resistance of the 1050 °C/2 h process improved with a hardness of 40.6 HRC, an increase of 26.1%, and a maximum relative abrasion resistance improvement of 84.63%. Which strengthening mechanism was mainly coating dendrites coarse and uniform diffusion occurs, martensite uniform phase transition presented on the surface, coating austenite grain size 9.08 µm smaller, martensite recrystallization and larger grain size of 28.57 µm, the coating as a whole in the uniform phase transition and dendritic crystal strengthening synergistic effect, hardness increased, resistance to wear became stronger. [ABSTRACT FROM AUTHOR]

This study investigated the influence of high silicon (4.2 wt%) and varying aluminum (3.5–4.8 wt%) content on the high temperature oxidation behavior and thermophysical properties of SiMoAl vermicular graphite cast iron for hot-end exhaust components. Isothermal oxidation tests at 800 °C and nonisothermal oxidation tests in a dry-air atmosphere were conducted on SiMo nodular iron, along with two SiMoAl vermicular graphite cast iron variants alloyed with 3.5 wt% Al and 4.8 wt% Al. The investigations revealed the formation of a thin duplex layer of oxide scale, consisting of an iron-rich external oxide layer and continuous aluminum oxide at the metal/oxide interface. Although aluminum oxide acted as a protective barrier by impeding the solid-state diffusion of oxygen, severe subsurface oxidation was observed due to the interconnected vermicular graphite covered by aluminum oxides after decarburization. Furthermore, based on nonisothermal oxidation experiments, the effective activation energy of oxidation was found to be significantly increased by the addition of aluminum, even though the oxidation activation energies of SiMoAl samples exhibited small changes in comparison to each other. Additionally, thermophysical analysis demonstrated a substantial decrease in the thermal conductivity and a slight increase in the thermal expansion with the addition of aluminum. [ABSTRACT FROM AUTHOR]

Experimental and FEM studies of the friction welding process of spheroidal graphite cast iron (SGCI) are presented. A coupled thermal and mechanical 2.5 D FEM model was used to simulate the continuous drive friction welding (CDFW) process. The FE model predicted the peak temperature of the joint, effective stress, axial shortening, and the weld flash size. Additionally, the friction force on the axial shortening of specimens was studied. The peak temperatures were measured both on the axis and at the surface of the specimen. The predicted maximum temperatures in the axis, ½ radius, and 2 mm from the surface of the sample amounted to 1162 °C, 1177 °C, and 1061 °C, respectively. The maximum temperature of the spheroidal graphite cast iron joint was below the melting temperature of the base material (~1350 °C). The predicted temperature curves, outbursts, and shortening of welded elements indicated a good match with real models. [ABSTRACT FROM AUTHOR]

The article discusses a research project called "nodularWELD" that investigates the fatigue behavior of welded thick-walled nodular cast iron components used in heavy industry and wind energy turbines. The study examines the effects of local material defects on the lifetime of these components and explores the possibility of repair welding. The research project examines different welding fillers and conducts fatigue tests to assess the usability of repair-welded nodular cast iron. The findings show a reduction in fatigue strength for all materials in the welded condition, with the highest loss observed for EN-GJS-450-18. The research suggests that welding for repair purposes may not be feasible for certain applications. The document also includes a list of nomenclature, references, and acknowledgments to the funding source and project partners. [Extracted from the article]

It is important to improve the comprehensive performance of the ductile iron bars (DIBs) for the cylinder block of the extra high pressure hydraulic plunger pump and accelerate the industrial application. In this work, the LZQT600-3 DIBs with the diameter of 145 mm were prepared by the horizontal continuous casting (HCC) process, that is, LZQT600-3 HCCDIBs. The microstructure and room temperature tensile properties of different sections [left-edge (surface layer), left-1/2R (left half of the radius), and the center of the HCCDIBs] were studied. The results show that the spheroidization of LZQT600-3 HCCDIBs matrix from the left-edge, left1/2R to the center is at nodulizing grade II and above. As the cooling rate gradually decreases from surface to the center of the HCCIBs, the number of spheroidized graphite is gradually reduced, the size is gradually increased, the shape factor is decreased, and the pearlite content and lamellate spacing are increased. Along the horizontal direction of the section, the hardness of the material is distributed symmetrically around the center of the HCCDIBs. In the vertical direction, the hardness distribution in the center of the HCCDIBs is asymmetrical due to the gravity during the solidification process. Therefore, the microstructure in the lower part of the section solidifies relatively quickly. The left-edge has the best tensile mechanical properties, and the ultimate tensile strength, yield tensile strength and elongation are 597.3 MPa, 418.5 MPa and 9.6%, respectively. The tensile fracture belongs to the ductile-brittle hybrid fracture. The comprehensive performances of LZQT600-3 HCCDIBs meet the actual application requirements of ultra-high pressure hydraulic plunger pump cylinder. [ABSTRACT FROM AUTHOR]

Temperature has a great influence on the mechanical properties of ductile cast iron or nodular cast iron. A thermomechanical treatment was carried out at various elevated temperatures of 450 °C, 750 °C and 850 °C using a universal testing machine with a tub furnace. Specimens were held at these temperatures for 20 min to ensure a homogeneous temperature distribution along the entire length of the specimen, before a tensile load was applied. Specimens were deformed to various levels of uniform strain (0%, 25%, 50%, 75%, and 100%). These degrees of deformation were measured with a dial gauge attached to a movable cross plate. Three strain rates were used for each specimen and temperature: 1.8 × 10 − 4   s − 1 , 9 × 10 − 4   s − 1 and 4.5 × 10 − 3   s − 1 . A simple analytical model was extracted based on the CT tensile test geometry and yield stress and a 0.2% offset strain to measure the fracture toughness (JIC). To validate the analytical model, an extended finite element method (XFEM) was implemented for specimens tested at different temperatures, with a strain rate of 1.8 × 10 − 4   s − 1 . The model was then extended to include the tested specimens at other strain rates. The results show that increasing strain rates and temperature, especially at 850 °C, increased the ductility of the cast iron and thus its formability. The largest percentage strains were 1 and 1.5 at a temperature of 750 °C and a strain rate of 1.8 × 10 − 4   s − 1 and 9 × 10 − 4   s − 1 , respectively, and reached their maximum value of 1.7 and 2.2% at 850 °C and a strain rate of 9 × 10 − 4   s − 1 and 4.5 × 10 − 3   s − 1 , respectively. In addition, the simple and fast analytical model is useful in selecting materials for determining the fracture toughness (JIC) at various elevated temperatures and different strain rates. [ABSTRACT FROM AUTHOR]

Medium-alloy ductile iron with a SiMo ferritic matrix has very good heat resistance. The addition of chromium and aluminum also increases this resistance. This article presents the impact of chromium and aluminum on the structure of SiMo cast iron, especially their impact on the deformation of the spherical graphite precipitates and the formation of M6C and M3C2 carbide phases. These carbides are formed in a ferritic matrix or at the grain boundaries, resulting in increased hardness and a drastic reduction in impact strength. The article presents the influence of heat treatment on the material's microstructure and resistance to abrasive wear. Chromium and aluminum additions can also indirectly reduce the abrasive wear resistance of SiMo cast iron. The presented research shows the possibility of doubling the abrasive wear resistance of SiMo cast iron. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1063785024340017 [ABSTRACT FROM AUTHOR]

The microstructure of the in situ TiC-reinforced composite surface layers developed during laser surface alloying of a ductile cast iron substrate with titanium was related to the solidification conditions in the molten pool. The solidification conditions were estimated using infrared thermography. It was found that the cooling rates of the melt up to about 700 °C/s enable the complete reaction between carbon and the entire amount of titanium introduced into the molten pool. In turn, the cooling rate of about 280 °C/s for the melt containing 8.0 wt% Ti allows the TiC particles to grow in the dendritic form with well-developed secondary arms and a total size of up to 30 µm. For a constant Ti content, the cooling rate of the melt had no effect on the TiC fraction. The increase in the cooling rate elevated the retained austenite fraction in the matrix material, lowering its hardness. [ABSTRACT FROM AUTHOR]

Austempered ductile iron is an innovative material obtained by subjecting it to an austempering heat treatment. The wide application of this material is because its properties are comparable to those of steel, which has a much lower weight. However, the machinability of this material is always a difficult task owing to its high hardness. This problem becomes more complex when a considerable amount of Mn is added. In this study, a novel two-step austempering heat treatment was performed on spheroidal graphite iron containing different amounts of manganese. Although the novel heat treatment method helps to obtain a superior combination of hardness and impact, its effect on machinability must be determined. This study provides the results of machinability tests carried out on austempered ductile iron with various manganese contents produced using the novel method. Scanning electron microscope images of the microstructures revealed a typical ausferrite structure with no segregation of manganese at the grain boundary. This is evident from the good tool life obtained in the machinability tests. Regression equations are fitted to determine the tool life and surface roughness for machining parameters with a range of values considered in this study. The results obtained have shown that till 1 wt% of manganese alloyed austempered ductile iron can be successfully produced using the novel heat treatment method. This helps to obtain the optimum combination of strength and impact properties. [ABSTRACT FROM AUTHOR]

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