Metallurgical Transformations Research Articles

Advances in Heat Treatment and Microstructural Optimization of Hadfield Steel for Enhanced Wear Resistance

Objective: This study aims to explore the impact of heat treatment processes on carbide formation in Hadfield steel, focusing on optimizing its microstructure and mechanical properties for industrial applications that require high wear resistance. Theoretical Framework: The research is grounded in theories of metallurgical transformation and work hardening, particularly in relation to the metastable austenitic structure of Hadfield steel, which transforms into martensite under impact. This transformation mechanism, alongside alloy composition and heat treatment, shapes the steel’s resistance to wear and mechanical strength. Method: A systematic literature review was conducted, encompassing 11 relevant studies on Hadfield steel from four scientific databases: Taylor & Francis, Springer, Wiley, and ScienceDirect. The selected studies were analyzed using the PRISMA methodology to evaluate the influence of heat treatments—such as austenitization, quenching, and tempering—on carbide formation and microstructure. Results and Discussion: Findings reveal that specific heat treatments significantly enhance Hadfield steel’s wear resistance and strength. The influence of processes like austenitization on carbide dissolution and rapid cooling to avoid carbide precipitation has proven critical for the steel’s toughness. This discussion aligns the observed improvements with theoretical predictions and identifies challenges in carbide control for enhanced performance. Research Implications: The study provides practical insights for industries utilizing Hadfield steel in high-wear environments, such as mining and transportation, and proposes further research into innovative heat treatment strategies. Originality/Value: This study contributes novel perspectives on the optimization of Hadfield steel's heat treatment processes, potentially informing advanced manufacturing techniques to improve the steel’s durability and economic value in key industrial applications.

A new approach to investigate secondary hydriding phenomenon on M5Framatome clads under high–temperature LOCA conditions

The focus of this study is about a new experimental approach for a separate effects study of the secondary hydriding phenomenon under LOCA conditions. Many nuclear institutes perform semi–integrals tests to study the cladding behaviour during a LOCA transient. Those tests combined several phenomena and performing a detailed analysis of the secondary hydriding phenomenon using these tests can be challenging. A dedicated experimental protocol aiming at simulating secondary hydriding has been set up. Separate effects tests (SETs) were then carried out using this protocol to study the effects of both oxidation duration and temperature, on the hydrogen absorption during the oxidation stage of the LOCA transient on M5Framatome11M5 and M5Framatome are trademarks or registered trademarks of Framatome or its affiliates, in the USA or other countries. cladding. The effects of gap size were also investigated. Metallographic analysis has been used to characterise the M5Framatome clad metallurgical transformation after the high–temperature (HT) oxidation.

A fully-coupled FEM-based 2D metallo-thermo-mechanical model of laser-assisted machining of Ti-6Al-4V - a focus on residual stresses

The complex interaction between the laser beam, the workpiece, and the cutting tool during laser-assisted machining (LAM) can result in considerable thermal gradients, variational strains and microstructural phase transformations, ultimately leading to residual stresses. This study presents a finite element-based model for the LAM of Ti-6Al-4V alloy, integrating the material’s metallurgical transformations and thermo-mechanical behaviour to predict residual stresses. The thermal, mechanical, and metallurgical aspects of the LAM process are fully-coupled in the model, accurately capturing chip formation and serration, while also accommodating strains induced by metallurgical transformations. Implemented within the finite element software, ABAQUS, the model’s predictions for surface residual stresses align closely (¿90%) with experimental data from literature. Notably, the model elucidates the transition of surface residual stresses towards tensile nature due to laser heating in LAM. The results reveal that the metallurgical transformation exerts a more pronounced influence at lower cutting speeds. Moreover, surface residual stresses tend towards tensile nature with increased laser power but shift towards compressive nature with higher laser-tool gap, cutting speed, and feed. Depth-wise residual stress distributions underscore the significant impact of laser power, speed, and feed compared to laser-tool gap. The proposed model can be used to optimise the LAM process and improve the quality and reliability of the finished products.

Analysis of Residual Stresses in Curved Cutouts of Steel Box Girder Transverse Diaphragms

In order to analyze the characteristics of cutting residual stress distribution at the arc‐shaped cutout of steel box girder diaphragm and to study its fatigue cracking mechanism. Taking Xia Zhang Bridge as the engineering background, this paper proposes a systematic method for calculating the residual stress field at the arc‐shaped cutout of the diaphragm. First, a mathematical model of the cutting heat source was established for predicting the temperature field changes during the cutting process of the diaphragm. Then, a 3D thermoelastic‐plastic finite element model was established using Abaqus to parametrically analysis the residual stresses during the fabrication of the transverse spacer. The results show that the cutting heat source creates a “thermal stagnation” effect at the curved notch, which leads to the local metallurgical transformation of the metal surface layer, which is unfavorable to its fatigue performance. The residual stresses are mainly concentrated near the cutting line, and the transverse residual stresses are lower at the free edge of the cutting line, which is easy to crack, and higher in the middle of the arc section of the arc notch. Inside the transverse bulkhead, at 14.5 mm from the free edge of the cut, in addition to the existence of high longitudinal residual tensile stress, its transverse residual tensile stress is also high, with a peak value of 199.3 MPa. Thermal cutting produces high residual tensile stress at the free edge, and the tensile stress cycle formed under the combined effect of wheel load is one of the reasons for the formation of initial fatigue cracks.

Influence of Strain Rate on Metallurgical and Mechanical Properties of Friction Stir Spot Welded Aluminium Joints

Nowadays, the substitution of copper with aluminium is widely pursued in order to save weight and material costs, for battery components and wire connectors. Additionally, cost reductions can be further enhanced with effective reduction of energy consumption through efficient manufacturing. Therefore, friction stir spot welding as a solid-state welding technique is a potential choice with low energy demands and high joining performances. However, the joining of aluminium and its alloys with solid-state welding techniques is still a challenging task due to a persistent and chemically stable aluminium oxide layer formed at the sheets prior to the welding, due to the reaction between aluminium and atmospheric oxygen. In this paper, the influence of strain rate induced during friction stir spot welding process on the metallurgical, mechanical and electrical properties of friction stir spot welding of AA 5754-H111 was studied. The strain rate was calculated according to the rotational speed of the tool and the effective (average) radius and depth of the stir zone. It was observed that the specimens welded with a lower strain rate endured a 15 % higher average strain failure load compared to the specimens welded at a higher share rate. The microhardness profiles of the specimens obtained at low strain rates imply strain hardening mechanisms in the weld zone, while the microhardness of specimens welded at high strain rates expressed thermal softening. It was also found that the friction welded sheets, regardless of the strain rate, show increased electrical resistance compared to the base material, however, it decreases with an increase in strain rate. Microstructural analysis reveals a stress-induced metallurgical transformation in the narrow zone around the weld-faying interface.

Mechanical analysis and machinability evaluation of a new EDM-turning hybrid machining process

This study developed an accurate electrical discharge-assisted turning (EDAT) technique for Ti–6Al–4 V alloy and a precise EDAT cutting force prediction model considering theoretical multi-physics fields with metallurgical transformation. A heat-fluid coupled model of multi-pulse discharge in the EDAT process was developed to obtain the thickness of the removal layer (RL) and modified layer (ML) together with the temperature field of the cutting layer. Subsequently, the shear flow stresses under different machining parameters were obtained using the oblique cutting and flow softening constitutive models. Within the cutting layer, the pure thermal softening effect reduces the flow stresses by more than 25% in the unmodified matrix layer (UML) and by more than 60% in the ML, which is dominated by the metallurgical transformation softening (MTS) effect. Finally, the cutting force model of EDAT under multi-physical fields was established and the accuracy was verified by relevant experiments. The results showed that the increase in discharge number accelerated the rise of workpiece surface temperatures, and the small cutting parameters were favorable to the machining performance of the EDAT. The MTS effect significantly reduces cutting forces while improving the quality of the machined surface.

Optimizing porosity detection in wire laser metal deposition processes through data-driven AI classification techniques

Additive manufacturing (AM) is an attractive solution for many companies that produce geometrically complex parts. This process consists of depositing material layer by layer following a sliced CAD geometry. It brings several benefits to manufacturing capabilities, such as design freedom, reduced material waste, and short-run customization. However, one of the current challenges faced by users of the process, mainly in wire laser metal deposition (wLMD), is to avoid defects in the manufactured part, especially the porosity. This defect is caused by extreme conditions and metallurgical transformations of the process. And not only does it directly affect the mechanical performance of the parts, especially the fatigue properties, but it also means an increase in costs due to the inspection tasks to which the manufactured parts must be subjected. This work compares three operational solution approaches, product-centric, based on signal-based feature extraction and Topological Data Analysis together with statistical and Machine Learning (ML) techniques, for the early detection and prediction of porosity failure in a wLMD process. The different forecasting and validation strategies demonstrate the variety of conclusions that can be drawn with different objectives in the analysis of the monitored data in AM problems.

Online Grain Size Measurement by Laser Ultrasonics in a Hot Rolling Mill

Laser ultrasonics (LUS) has shown through numerous studies and in-situ laboratory experiments, its suitability to track microstructural features evolution as well as metallurgical transformation in steels during thermal cycles with temperatures reaching 1250°C. This prior work has motivated the use of this technology to be in applied in an industrial hot strip mill (HSM) in Eisenhüttenstadt, Germany. For this purpose, a transportable trolley which embedded LUS components (Generation and Detection Lasers, Two-Wave Mixing Interferometer, Dedicated Fibered Optical Head) was designed. The industrial investigation was carried on moving strips during normal production at several locations of the HSM, resulting in signals for high-strength lowalloy (HSLA) and advanced high-strength steel (AHSS) grades. The development of a specific data processing tool allowed calculating the grain size from the analysis of the online recorded signals. Such results were then compared to predictions from metallurgical models, finding reasonably close values. LUS appears as a suitable solution to monitor microstructural features and metallurgical transformations occurring in steel in a Hot Strip Mill (HSM) line. This approach could enable in the future the development of more reliable models and control loop of the process. This action was supported by the European commission and led by a consortium composed by ArcelorMittal, Imagine Optic and IMI-NRC.

Thermo-metallurgical-mechanical modeling of FG titanium-matrix composites in powder bed fusion

The build-up of residual stress plays a crucial role in the formation quality of as-built parts fabricated by powder bed fusion (PBF). However, the comprehensive understanding of residual stress and distortion fields in PBF-printed functionally graded titanium matrix composites (FGTMCs) has not been achieved. Furthermore, the effect of metallurgical transformation on thermo-mechanical behavior of these materials during the PBF remains unclear. In this paper, considering the phase transition effect due to thermal evolution in the PBF process, a thermo-metallurgical-mechanical coupled model of printed FGTMCs is developed. The equivalent temperature-dependent elastic modulus and heat conductivity of FGTMCs are calculated based on the homogenization method. The differential quadrature method is first employed to efficiently predict the temperature, residual stress, and distortion distributions of PBF-printed FGTMCs. The accuracy of the proposed model is verified by a comparison with predictions in the literature. Furthermore, the effect of crucial process and geometrical parameters on the thermo-mechanical behaviors of FGTMCs is analyzed. The results indicate that the residual stress and vertical distortion of FGTMCs increase as the laser penetration, energy densities, and power index increase, while decreasing significantly with the increased ceramic content, preheating temperature, and layer thickness. These results provide valuable insights for guiding the process optimization of additively manufactured FGTMCs.

Exploring the Optical and Electrical Characteristics of MgO/SiC-H2O Nanofluids for Thermal Energy Storage

Heat is transferred to storage medium during the charging phase of thermal energy storage (TES), and it is then released during the discharging phase. It may be used to industrial operations like metallurgical transformations or solar power facilities. Heat is stored in materials that alter temperature, phase, or chemical composition in sensible, latent, and thermochemical media, respectively. Optimal heat storage has a long history. This study describes investigating the optical and electrical properties of MgO/SiC-H2O nanofluids for applications including thermal energy storage. Results indicate that when MgO/SiC NP concentrations were raised to 1.2 gm/L, absorbance rose by approximately 66.9% and transmittance by about 54%. Additionally, the increase in MgO/SiC NP concentration will raise absorbance, which indicates improved nanofluid dispersion. Additionally, when MgO/SiC nanoparticle concentrations approach 1.2 gm/L, the electrical conductivity of nanofluids increases by roughly 49.2%, and the melting time reduces as the concentration of MgO/SiC nanoparticles rises.

Flow stress modeling of a new HSLA steel by Zerilli-Armstrong model

The selection of an appropriate constitutive model is vital for the design of thermo-mechanical treatment as it describes the flow patterns and governs the metallurgical transformations. In this research, the constitutive behavior of a newly developed high-strength steel has been studied employing a physical-based Zerilli-Armstrong model. For this purpose, the experimentally generated stress–strain data from isothermal compression tests performed over a wide range of temperatures (1073–1323 K) and strain rates (0.01–10 s−1) have been considered. The constitutive relationships of flow stress as functions of temperature, strain rate, and true strain have been developed for both original and modified Zerilli-Armstrong models. The comparison between the measured and predicted flow stresses demonstrates better predictability of the modified model with a higher correlation coefficient (R = 0.982) and a much lower average absolute relative error (AARE = 7.31%) since the values of R and AARE for the original model are 0.845 and 23.96%, respectively. The better accuracy of the modified Zerilli-Armstrong model is attributed to the fact that it additionally considers the coupled effects of temperature and strain, unlike the original Zerilli-Armstrong model.

Thermal stress analysis in hot rolling process

In continuous hot slab rolling, it is important to know the temperature distribution within the strip along the length of the rolling mill because the dominant parameter controlling the kinetics of metallurgical transformations and the flow stress of a rolled metal is temperature. A mathematical model based on finite difference method is utilized to predict the temperature distribution and microstructural changes during the continuous hot slab rolling process. The effects of various parameters such as heat of deformation, the work-roll temperature, the rolling speed, and the heat transfer coefficient between the work-roll and the metal were all taken into account in the analysis. From the parametric analysis carried out, it was shown that the temperature in the deformation zone increases as the percentage reduction in the strip thickness and the rolling process, it affects the temperature distribution in the work-roll significantly , the heat generation on the strip-roll interface increases significantly when the percentage reduction in the strip exceeds a certain value. It was also shown that at low rolling speed, the temperature increase is uniform inside the strip and the roll and the maximum temperature of the strip occurs in the neighborhood of the strip centerline region.

Metallographic method for temperature measurement: Reconstruction of grinding temperature field based on critical austenitizing depth and cyclic feedback algorithm

Effectively measuring and predicting the grinding temperature is significant for accurately controlling machined surface quality. However, the spatial limitations of the contact area and the time-varying of heat sources make the accurate acquisition of grinding temperature challenging. Existing methods have made critical achievements, but further exploration is still desired. To this end, a metallographic method for temperature measurement is proposed, which uses the thermal reference reflected by metallographic images combined with a cyclic feedback algorithm to reconstruct the grinding temperature field. Specifically, dry grinding thermal-force synchronous measurement experiments are carried out for carbon steel, and the mapping relationship between the grinding heat transient characteristics and metallurgical transformations diversity in the surface material is established. The improved image recognition algorithm is applied with metallographic detection to achieve accurate localization of the critical austenitizing depth. Afterwards, a cyclic feedback algorithm based on differential heat transfer is proposed to solve the dynamic distribution of the grinding temperature field (error within 10%) under random heat sources. The results show that the parabolic heat source can better describe the distribution of heat flow density in the contact area under dry grinding, and the heat flow into the workpiece is about 30% of the total energy. This study fills the blank of the metallographic method for solving grinding temperature, which helps profoundly understand the interaction mechanism between processing heat and metallurgical transformation and promotes the development of advanced temperature measurement and prediction technology.

A comprehensive evaluation of tempering kinetics on 3rd generation advanced high strength steels

Emerging third-generation advanced high strength steels (3G AHSS) grades are being increasingly considered for autobody applications owing to their complex microstructures providing an excellent combination of strength and ductility. When welded with RSW, 3G AHSS such as 3G 1180 and 3G 980, exhibits a solid-state transformation in the sub-critical-heat-affected-zone (SCHAZ) due to the heat generated during the RSW process. The resulting changes in microstructure can affect the mechanical properties of the material within and around the spot welds and thereby influence the performance of welded components in case of a vehicle crash event. To study metallurgical transformations in the SCHAZ during the RSW process, 3G 1180 and 3G 980, and a reference martensitic press hardened steel, PHS 1500, were selected. These materials were subjected to isothermal tempering experiments at temperatures ranging between 350 °C and 650 °C and different tempering times from 0.2 s to 24 h. It was shown that the Hollomon-Jaffe model accurately describes the tempering kinetics of 3G 1180 and PHS 1500 but does not predict the transformation processes in the SCHAZ of 3G 980. The PHS 1500 and 3G 1180 showed softening (tempering) for all combinations of investigated tempering times and temperatures due to the decomposition of martensite. In contrast, the 3G 980 showed a combination of softening by the formation of martensite and secondary ferrite combined with secondary hardening due to the formation of fine M2C typed plate-like carbides. Furthermore, during long tempering, the M2C particles dissolve into the matrix and were replaced by cementite particles in 3G 980.

Microstructure-based multiscale and heterogeneous elasto-plastic properties of 2205 duplex stainless steel welded joints: Experimental and modeling

This work aims to reveal the inherent dependency between the heterogeneous microstructure induced by the metallurgical transformation during welding of 2205 duplex stainless steel (DSS) and its macroscopic and microscopic elasto-plastic properties by experiments and models. A multiscale model was developed by combining a macro-constitutive model incorporating the physically-based yield strength and a crystal plasticity model considering both the micro-mechanical properties of two phases and their realistic morphology. The results show that the heterogeneous macro-mechanical properties of base metal (BM), heat affected zone (HAZ), and weld material (WM), as well as their micro-mechanical responses related to phase morphology, ratio, and grain size, can be accurately predicted. The contribution of Peierls–Nabarro stress, solid solution strengthening, grain/phase boundary, and dislocations density on macro-yield and tensile strengths was quantified, and WM was proven to have greater yield and tensile strengths due to the greater contribution of grain refinement and solid solution strengthening. In addition, a transition mechanism of the deformation-bearing phase from austenite to ferrite with the increase of load was proved, and the banded grain boundary austenite (GBA) and its adjacent ferritic grains were prone to plastic-deformation. This work can be used as guidance of structure integrity assessment and welding process optimization for the engineering components of DSS.

Computational Modeling of Thermo-Metallurgical Behavior During the TIG Welding Process

Welding is widely used in the aerospace, naval and automotive industries. Since high temperatures are involved in this process, solid state metallurgical changes are expected. These metallurgical changes can induce deformations and residual stresses in welded parts. The objective of this work is to develop a finite element calculation code, under the MATLAB environment, to predict the evolution of the various metallurgical transformations during TIG welding of C50 steel plates. In the proposed calculation procedure, we used Leblond’s equation and Waeckel’s model to characterize the metallurgical transformations during respectively heating and cooling stage. We also taken into account the effect of austenitic grain size on metallurgical transformations evolution. Thermal properties are introduced according temperature and phase proportions present during welding operation. Simulation results show that the metallurgical structure in the heat affected zone (HAZ) is largely related to welding thermal power and the plate preheating temperature. We compared simulation results to experimental measurements and the efficiency of the developed computational code was confirmed.

Surface state change influence’s theoretical approach of pressed iron on hollow cathode discharge characteristics: first results of plasma heating reproducibility for sintering purposes

In this work first results of the plasma heating process reproducibility for sintering purposes of pressed iron powder sample was investigated analyzing changes on the current-voltage characteristics of pulsed direct current (dc) Ar + H2 hollow cathode discharges sequentially carried out. For this purpose, the temperature of a sample acting as central cathode was varied by changing the switched-on time (duty cycle) of the pulse, via plasma species bombardment (ions and fast neutrals), which typically occurs in both cathode cylindrical surfaces that constitute the annular (hollow cathode) glow discharge, and measured by a thermocouple inserted in the central cathode sample holder. After two sequential plasma heating experiments, the third one practically reproduced the measured plasma parameters evidenced in the second heating, and the respective heating curves as a function of the time have led to similar current-voltage characteristics suggesting the iron sample sintering in non-isothermal way. Principles comprising plasma-surface interface and metallurgical-physical-chemical reactions, powder surface aspects, thermodynamic properties, metallurgical transformation of the pressed sample, and hollow cathode discharge properties are presented and discussed. The main points considered in the present approach are related to plasma (oxygen-affected plasma ionization, high ionization and excitation rate, and the intense light radiation of the annular glow discharge), thermodynamics (oxidation-reduction reactions, electron work function, sintering driving force, and surface energy), and powder (particle size distribution, morphology, specific surface, and iron recrystallization). To the best of the author’s knowledge, it is the first time that it is brought to the light the changes on hollow cathode discharge characteristics while an iron sample acting as the central cathode of an annular glow discharge is subjected to distinct heating steps on the temperature range of 20 to ∼1250 °C, leading it to have its sintering initiated.

Corrosion, Heat Treatment, and Microstructural Studies of GTA Welded 316 Austenitic Stainless-Steel Joint

The formation of a protective chromium carbide passive film makes austenitic stainless steel (ASS) alloys suitable for corrosive and high-temperature environments. This paper examined the transformation of the microstructure, corrosion, and mechanical properties of gas tungsten arc welded 316 austenitic stainless steel. The scientific principles governing metallurgical transformation and corrosion dynamics were discussed. The review shows that passive film on 316L ASS gradually erodes as the concentration of chloride ion rises. Metallurgical properties of FZ are completely changed, and solid-state transformation occurs at HAZ during the GTA welding process. These transformations affect the microstructure, corrosion, and mechanical properties of GTA welded ASS alloys.

Parametric analysis and machine learning-based parametric modeling of wire laser metal deposition induced porosity

Additive manufacturing is an appealing solution to produce geometrically complex parts, difficult to manufacture using traditional technologies. The extreme process conditions, in particular the high temperature, complex interactions and couplings, rich metallurgical transformations and combinatorial deposition trajectories, induce numerous process defects and in particular porosity. Simulating numerically porosity appearance remains extremely complex because of the multiple physics induced by the laser-material interaction, the multiple space and time scales, with a strong impact on the simulation efficiency and performances. Moreover, when analyzing parts build-up by using the wire laser metal deposition —wLMD— technology it can be noticed a significant variability in the porosity size and distribution even when process parameters remain unchanged. For these reasons the present paper aims at proposing an alternative modeling approach based on the use of neural networks to express the porosity as a function of different process parameters that will be extracted from the process analysis.

Fractographic Analysis of Mechanical Properties of Microalloyed Steel

Extensive efforts made over the past few decades have enhanced the rising performance of High-Strength Low-Alloy steels. Use of thermomechanical processing was considered for this research. However, the desired mechanical properties are obtained by formulating alloys. Further, to enhance mechanical properties, impact energy, the subsequent quenching and tempering are used. The metallurgical transformation caused by deformation followed by cooling and/or heat treatment has added influences on steels’ mechanical properties. The rational decrease in impact energy value is complex.