Search

Effects of transformation temperature and carbon content on the effective grain bounded by high‐angle boundary, i.e., “Bain size”, in bainite structure are studied in Fe–2Mn–(0.05–0.75)C (mass%) alloys transformed isothermally between 773 and 673 K. Bainitic ferrite (BF) nucleates at austenite (γ) grain boundary with strong variant selection for carbon content less than 0.2 mass%, resulting in formation of coarse BF regions consisting of the Kurdjumov–Sachs (K–S) variants belonging to the same Bain variant. As temperature is lowered, K–S variant pairs with large misorientation are frequently formed. Variant selection at γ grain boundary becomes weaker for higher carbon content due to frequent intragranular nucleation particularly at 673 K. The Bain size decreases generally as transformation temperature is lowered, which is ≈15 μm at 773 K but down to ≈5 μm at 673 K, and also slightly decreases at 773 K with increasing carbon content. At lower temperatures, it decreases with the increase of carbon content in low carbon range less than 0.2 mass%C but inversely increases in higher carbon range. The observed changes in the variant paring and the Bain size are well understood in terms of the driving force of BF formation and self‐accommodation of transformation strain. [ABSTRACT FROM AUTHOR]

In this study, we explore the evolution of martensitic structures during deformation and their correlation with solution temperature in a metastable β-type Ti–10V–2Fe–3Al alloy. After a solution treatment at 760 °C, microstructures consist of equiaxed β grains and primary α particles. Increasing the solution temperature to 780 °C minimally affects equiaxed β grain size (~4.1–4.7 μm) but significantly reduces the α phase volume fraction. The α particles become scarce and completely absent following solution treatments at 800 and 820 °C, where the β grain size grows to ~109.1 and ~151.3 μm, respectively. Thermally-induced martensite (TIM) α″ laths are formed in specimens solution-treated at 770 °C or higher, predominantly populating the β grains of the specific specimens solution-treated at 800 and 820 °C. All solution-treated specimens exhibit a double yielding phenomenon. For specimens solution-treated at 760–780 °C, this results primarily from the stress-induced martensitic transformation (SIMT) process, while for those solution-treated at 800 and 820 °C, it mainly arises from the martensite reorientation (MR) process. The triggering stress for the SIMT/MR process increases with increasing solution temperature. In early deformation stages, TIM α″ laths initially undergo the MR process, transforming into a favored α″ variant, and the SIMT process can occur concurrently. As deformation progresses, the α″ phase changes orientation continuously through deformation twinning, transforming into the favored α″ variant dictated by the evolving stress conditions. This study provides insights into martensitic structure evolution and its influence on mechanical properties in metastable β titanium alloys. [ABSTRACT FROM AUTHOR]

In this study, the decomposition of a martensite/austenite (M/A) microconstituent in bainitic steels was analyzed using differential scanning calorimetry (DSC) data in conjunction with Kissinger's and Johnson–Mehl–Avrami–Kolmogorov (JMAK)'s formulas. In bainitic steel subjected to austempering heat treatment, the presence of an M/A microstructure adversely affects the mechanical properties. According to the kinetic equations derived, it is observed that after tempering the sample at 600 °C for 4000 s, the generation of each phase reaches its maximum. The SEM images taken before and after tempering reveal extensive decomposition of the M/A constituent in the microstructure. The proportion of the M/A microstructure decreased significantly from about 10% before tempering to less than 1% after. Additionally, the content of residual austenite also reduced nearly to zero. These observations are consistent with the predictions of the kinetic equations. [ABSTRACT FROM AUTHOR]

Hardening of carbon steel products by austenitization and immersion in a quenching medium is a widely used heat treatment to obtain a hard and strong martensitic structure. To avoid the undesired consequences, such as residual stresses or insufficient hardening depth, the cooling rates must be accurately measured and controlled. This can be achieved using the impinging water jet quenching technique. The aim of this work is to perform hardening of four low‐alloyed 70 mm cylindrical carbon steel bars, using impinging water jet quenching technique with different jet flow rates, and to analyze its effect on thermal evolution and residual stresses. The temperature evolution during quenching experiments is recorded and used as input to a comprehensive quenching model to predict phase transformations, final hardness, and residual stresses of cylindrical bars. All four quenching experiments result in a fully hardened martensitic state. Furthermore, a decrease in jets' flow rate, within a certain interval, results in different thermal histories and in lower compressive residual stresses on the surface. The results from quenching simulations show promising hardness, microstructure, and residual stress predictions that are validated by hardness measurements, optical microscopy, and residual stress analysis using X‐Ray diffraction method. [ABSTRACT FROM AUTHOR]

To achieve the desired microstructural properties, the ongoing development and innovation in new structural steels require novel thermal processing. This study aims to improve the mechanical properties of a commercial spring carbon–silicon steel by tailoring its microstructure through a process involving quenching and partitioning (Q&P) followed by bainitic transformation. A two‐stage Q&P process is proposed to generate a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties demonstrate a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%. These values surpass those of conventional spring 9254 steel, highlighting the effectiveness of the thermal treatment design. Microstructure analysis reveals the presence of tempered martensite, bainite sheaves, nanoscale carbides, and aggregates of retained austenite. Moreover, the resulting body‐centered cubic matrix exhibits minimal lattice tetragonality of ≈1.0051, coupled with stable retained austenite featuring a carbon concentration of ≈3.42 ± 0.5 wt%, resulting in outstanding strength–ductility properties. These findings indicate that the proposed two‐stage Q&P process, followed by bainitic transformation, significantly enhances the mechanical properties of carbon–silicon steels, making it a promising candidate for high‐performance spring applications. [ABSTRACT FROM AUTHOR]

The effects of different quenching methods on the microstructure and mechanical properties of 30MnB5NbTi hot stamping steel are investigated, and the quenched microstructure is characterized by scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties are evaluated by uniaxial tensile test. The results reveal that, in comparison to die quenching, oil quenching, or air cooling, water‐quenched samples (tempered after water quenching, die quenching and oil quenching) exhibit the highest ultimate tensile strength (UTS) and yield strength (YS), reaching 2052 and 1422 MPa, respectively. Various quenching methods enable multi‐level strength control for the same steel grade, achieving a strength control range of ≈1000 MPa. The microstructure of samples quenched by water, die, and oil is fully martensite, and martensite exhibited block and lath morphology. With the increase of cooling rate, martensite laths become finer and the prior austenite size decreased. The microstructure of air‐cooled samples is martensite, ferrite, and retained austenite. The strengthening mechanisms of different quenched samples are calculated. The results show that dislocation strengthening and precipitation strengthening are the two dominant strengthening mechanisms in 30MnB5NbTi hot stamping steel. Therefore, the properties of hot stamping steel can be improved by changing the cooling rate by designing physical dies. [ABSTRACT FROM AUTHOR]

Phase transformations in cold-rolled (CR) 304L austenitic stainless steel were studied using different techniques, including dilatometry, X-ray diffraction and scanning electron microscopy. During continuous annealing, the dilatometric measurements indicated that the evolution of the deformed microstructures led to an important anomaly constituted of two contractions. Quantitative processing of the X-ray diffraction results allowed the determination of the temperature-dependence of α′-martensite and austenite (γ), phase fractions, dislocations density and lattice strains on heating to 900°C. It is demonstrated that the first contraction is due to the recovery of α′- and γ-phases. In this temperature range, it is suggested that the recovery in CR γ has caused the growth of surrounding α′ particles which competes with the reversion of the smallest α′ particles. The second contraction, on the other hand, has been attributed to the α′ reversion and recrystallization in CR γ regions. [ABSTRACT FROM AUTHOR]

This work proposes a thermodynamic-based constitutive model for shape memory alloy, which captures the gradual variation in stress–strain response from the shape memory effect to the pseudoelastic effect. The present model also provides a framework for modeling various other responses, such as strain temperature hysteresis and thermally induced strain recovery effect. The model classifies the different phases of the material, such as twinned martensite, detwinned martensite, and austenite, and the mix of these phases using only two internal variables, namely austenite volume fraction and inelastic martensite strain. The proposed model shows that introducing two independent yield conditions corresponding to each internal variable is sufficient to describe all the phase transformations. After presenting the theoretical framework of the model, the procedure for numerical implementation has been discussed. The simulation shows the gradual variation in the stress–strain curve at different temperatures in the phase transformation range and is observed to have an adequate quantitative agreement with the experimental data The model is further implemented for different shape memory alloys to show the possibility of the generalized framework for this class of materials. In addition, the capability of simulating other phenomena of SMA, such as strain response for thermal loading at constant stress and the complete response of strain recovery in shape memory behavior, is also presented. [ABSTRACT FROM AUTHOR]

The crystal structure and transformation path from austenite to 10M martensite in Ni–Mn–Ga single crystal are examined employing high‐energy synchrotron radiation, scanning, and transmission electron microscopy. Using temperature gradient, an austenite/twinned martensite interface is stabilized revealing the crystal structure and microstructure of both phases and the transformation sequence across the interface. Depending on the distance from the interface, three distinct types of martensite crystal lattice, namely simple tetragonal and two monoclinic modulated ones, that is, 10M′ and 10M are confirmed. In situ measurements show that lattice mismatch formed at the habit plane is compensated by the formation of micro‐twinned and branched martensite along with an elastic change in lattice parameters. It is shown that the characteristics for periodic shuffling twin boundaries, such as modulation twins or inverted stacking faults, are installed in later stages of transformation. In other words, large microstructure elements that most efficiently accommodate the strain are installed first, and then smaller elements are operable. Overall, the experimental results show that the crystal lattice does not adapt modulated phase at the habit plane and cannot be built up from simple non‐modulated tetragonal blocks but rather a specific sequence of phase transformations using shear/shuffling deformation takes place. [ABSTRACT FROM AUTHOR]

The effects of adding nickel on the phase transition temperature, microstructure, and mechanical properties of medium-carbon spring steel have been investigated. The results show that adding nickel reduces the martensite start (Ms) temperature, improves hardenability, and refines the sub-microstructure of the martensite, thereby improving yield stress. The yield strength of martensitic steel increases by approximately 100 MPa due to a synergistic combination of grain refinement strengthening and dislocation strengthening, with an increase in the nickel content from 0 wt.% to 1 wt.%. The cryogenic impact toughness of martensitic steel also improved with a higher nickel content due to packet and block refinement and an increase in the proportion of high-angle grain boundaries (HAGBs). [ABSTRACT FROM AUTHOR]

Low-alloy wear-resistant steel often requires the addition of trace alloy elements to enhance its performance while also considering the cost-effectiveness of production. In order to comparatively analyze the strengthening mechanisms of Mo and Cr elements and further explore economically feasible production processes, we designed two types of low-alloy wear-resistant steels, based on C-Mn series wear-resistant steels, with individually added Mo and Cr elements, comparing and investigating the roles of the alloying elements Mo and Cr in low-alloy wear-resistant steels. Utilizing JMatPro software to calculate Continuous Cooling Transformation (CCT) curves, conducting thermal simulation quenching experiments using a Gleeble-3800 thermal simulator, and employing equipment such as a metallographic microscope, transmission electron microscope, and tensile testing machine, this study comparatively investigated the influence of Mo and Cr on the microstructural transformation and mechanical properties of low-alloy wear-resistant steels under different cooling rates. The results indicate that the addition of the Mo element in low-alloy wear-resistant steel can effectively suppress the transformation of ferrite and pearlite, reduce the martensitic transformation temperature, and lower the critical cooling rate for complete martensitic transformation, thereby promoting martensitic transformation. Adding Cr elements can reduce the austenite transformation zone, decrease the rate of austenite formation, and promote the occurrence of low-temperature phase transformation. Additionally, Mo has a better effect on improving the toughness of low-temperature impact, and Cr has a more significant improvement in strength and hardness. The critical cooling rates of C-Mn-Mo steel and C-Mn-Cr steel for complete martensitic transition are 13 °C/s and 24 °C/s, respectively. With the increase in the cooling rate, the martensitic tissues of the two experimental steels gradually refined, and the characteristics of the slats gradually appeared. In comparison, the C-Mn-Mo steel displays a higher dislocation density, accompanied by dislocation entanglement phenomena, and contains a small amount of residual austenite, while granular ε-carbides are clearly precipitated in the C-Mn-Cr steel. The C-Mn-Mo steel achieves its best performance at a cooling rate of 25 °C/s, whereas the C-Mn-Cr steel only needs to increase the cooling rate to 35 °C/s to attain a similar comprehensive performance to the C-Mn-Mo steel. [ABSTRACT FROM AUTHOR]

The effects of austenitizing and austempering temperatures on the bainite transformation kinetics and the microstructural and mechanical properties of a medium-carbon high-silicon ultra-fine bainitic steel were investigated via dilatometric measurements, microstructural characterization and mechanical tests. It is demonstrated that the optimum austenitizing temperature exists for 0.3 wt.%C ultra-fine bainitic steel. Although the finer austenite grain at 950 °C provides more bainite nuclei site and form finer bainitic ferrite plates, the lower dislocation density in plates and the higher volume fraction of the retained austenite reduces the strength and impact toughness of ultra-fine steel. When the austenitizing temperature exceeds 1000 °C, the true thickness of bainitic ferrite plates and the volume fraction of blocky retained austenite in the bainite microstructure increase significantly with the increases in austenitizing temperature, which do harm to the plasticity and impact toughness. The effect of austempering temperature on the transformation behavior and microstructural morphology of ultra-fine bainite is greater than that of austenitizing temperature. The prior martensite, formed when the austempering temperature below Ms, can refine the bainitic ferrite plates and improve the strength and impact toughness. However, the presence of prior martensite divides the untransformed austenite and inhibits the growth of bainite sheaves, thus prolonging the finishing time of bainite transformation. In addition, prior martensite also strengthens the stability of untransformed austenite though carbon partition and enhances the volume fraction of blocky retained austenite, which reduces the plasticity of ultra-fine bainitic steel. According to the experimental results, the optimum austempering process for 0.3 wt. %C ultra-fine bainitic steel is through austenitization at 1000 °C and austempering at 340 °C. [ABSTRACT FROM AUTHOR]

Metastable austenitic stainless steels (MASS) are widely used in various industrial applications due to their exceptional mechanical properties. The microstructure of MASS can be regulated through severe plastic deformation, heat treatments, and surface treatments to achieve further improvement of mechanical properties. Herein, nanograin and quasiheterostructure are prepared by cold rolling and annealing process in Fe–17Cr–6Ni MASS. The mechanical response, deformation mechanism, and strengthening contribution of the two steels with representative microstructure are studied. The results indicate that nanograin austenitic steel (803 MPa, 22%) has superior yield strength and similar ductility compared with that of quasiheterostructure steel (600 MPa, 25%). In the nanograin steel, the deformation mechanism is mainly dislocation slip and deformation‐induced martensite transformation, while in quasiheterostructure steel, the deformation twinning is also included for the relative lower stacking fault energy in the coarse grain. The yield strength of nanograin structural steel is about 200 MPa higher than that of quasiheterostructure steel, which can be attributed to the differences in grain refinement strengthening, phase‐transformation strengthening, and precipitation strengthening of Cu particles. The findings presented in this study are informative for modulating MASS properties and ultimately improving the lifespan in a variety of industrial settings. [ABSTRACT FROM AUTHOR]

The current investigation delves into the influence of varying cooling rates, encompassing water, rapid quenching oil, and air, on the quench crack susceptibility (QCS) of disc springs. The assessment reveals that the average martensite lath width under water, oil, and air cooling conditions measures 0.61 μm, 0.66 μm, and 1.12 μm, respectively. Correspondingly, the residual austenite content amounts to 6.9%, 8.7%, and 12.3%. Notably, cracks are observed at the disc spring's perimeter during water cooling, whereas oil and air cooling effectively preclude such occurrences. Simulations demonstrate that residual stresses of up to 1011 MPa can arise at the disc spring cross-section corners under water cooling, significantly surpassing the stresses encountered under oil and air cooling, at 440 MPa and 73 MPa respectively. As the microstructure evolves, these residual stresses critically impact the grain boundaries of the original austenite, compromising the buffering capabilities of the martensite phase and residual austenite, thereby enhancing susceptibility to quench cracking. [ABSTRACT FROM AUTHOR]

To measure textures of hot rolled martensitic and bainitic steels, electron backscatter diffraction (EBSD) is applied to large areas, each covering about a thousand of prior grains. A scanning step is selected to keep reasonable time of the data acquisition still providing in any grain a significant number of analyzed points. Contributions to the transformation texture appearing from deformation and recrystallization components of the parent texture are estimated with the Bain relationship. To assess the parent austenite state, their proportion is then expressed by a scalar parameter. The results are verified by independent metallographic data. Avoiding the reconstruction of prior grains, this statistical approach will facilitate evaluation of complex austenite structures with comparable fractions of dissimilar material states. [ABSTRACT FROM AUTHOR]

Depending on the alloy composition, intercritical annealing may provide different phases in the microstructure. For low-alloyed dual-phase (DP) steels it is usually ferrite and martensite, while for medium-Mn steels retained austenite is also formed. In a present study, a wide intercritical temperature range was applied to a 5% Mn steel to investigate possible microstructure combinations: ranging from fully ferritic, through ferritic-austenitic, multiphase, to fully martensitic, which were next investigated in terms of mechanical properties to clarify the behavior of this type of material. The obtained results together with technological issues and economic indicators were next compared to mechanical properties of typical DP steels in order to assess the possibility of replacing this material in car production. The mechanical properties were evaluated using static tensile and hardness tests. The phase composition was determined qualitatively and quantitatively using dilatometry, X-ray diffraction measurements, and electron backscatter diffraction analysis. The results suggest that both initial austenite and martensite fractions have a decisive influence on the yielding and elongation of steel; however, the tensile strength depends mainly on the sum of martensite initially present in the microstructure and the strain-induced martensite formed from the plastically deformed austenite regardless of the initial retained austenite—martensite ratio. The results indicate superior total elongation of medium-Mn steels reaching 30% compared to DP steels with a similar strength level in the range between 900 and 1400 MPa. However, medium-Mn steels could be a significant competitor to dual phase steels only if some technological problems like discontinuous yielding and serrations are significantly reduced. [ABSTRACT FROM AUTHOR]

A multiphase‐gradient‐structured medium‐Mn steel with dislocation/stacking fault (SF) density gradient, austenite fraction gradient, and grain size gradient is designed and fabricated by cyclic torsion. It exhibits higher yield strength (YS) (942 MPa), ultimate tensile strength (1295 MPa), and tensile toughness (290 mJ mm−3) than its homogeneous counterpart (672, 1273 MPa, and 278 mJ mm−3, respectively). High‐density‐interlaced SFs are generated at the surface region because of the change in strain path and stress state during cyclic torsion. These massive interactive SFs promote the persistent martensite transformation of the retained austenite in the surface region within the entire uniform strain range. Therefore, in addition to the central layer, the surface region in the gradient structures provides strong strain hardening. Moreover, the continuous martensite transformation in the surface region allows the gradient structure to be retained even after tensile failure, which is beneficial for improving the heterogeneous‐deformation‐induced (HDI) hardening of the gradient‐structured sample during tensile deformation. Thus, the combination of active and persistent transformation‐induced plasticity effect and HDI hardening contributes to its excellent tensile toughness and ductility. Quantitative analysis indicates that HDI strengthening and dislocation strengthening play a dominant role in the sample's ultrahigh YS. [ABSTRACT FROM AUTHOR]

Understanding the effects of martensite volume fractions (V m) in dual phase (DP) steel resulting from heat treatment is crucial for designing structures for mechanical impact resistance and optimizing manufacturing processes. DP steel's material behaviour depends heavily on its microstructure properties. While stress-strain curves for individual phases in DP steels are often determined using empirical models, extensive experimental data is required to establish empirical model constants. This research aims to achieve two main objectives: firstly, to calibrate stress-strain curves for pure ferrite and pure martensite using limited experimental data using micromechanical adaptive iteration algorithm (MAIA). This calibration involves using stress-strain data from DP steels with varying V m during the calibration stage and additional data for verification. Secondly, to conduct a comprehensive sensitivity analysis of MAIA to assess its capabilities and limitations. Microstructure-based finite element (FE) models, simulated with ABAQUS/Standard, are employed to predict stress-strain curves under uniaxial tensile test conditions. The MAIA approach successfully calculated ferrite and martensite stress-strain curves that could predict plastic behaviour of DP steel with different V m, which agreed with experimental work. Key advantages of this approach include avoiding complex 3D microstructure geometries and requiring only two experimentally obtained stress-strain curves with different V m for material constant calibration, along with another curve for validation. However, the experimental data selected for calibration must have a V m difference between 20%–50% and one of the DP steels must have a low martensite volume fraction. The FE micromechanical model could capture the effect of softening of martensite phase and strengthening of ferrite phase as compared to its bulk properties for DP steel. The effect of V m on strain hardening rate was also successfully captured. This technique comes with obvious shortcomings, such as excluding crystal plasticity behaviour, and change in chemical composition within the individual phase with varying martensite volume fraction. [ABSTRACT FROM AUTHOR]

In the present study, a Ni–Cr–Mo–V alloyed ductile iron with high hardness was developed. The Ni–Cr–Mo–V alloyed ductile iron fabricated by horizontal continuous casting was composed of dendritic austenite, martensite, carbides and graphite nodules and exhibited a hardness as high as 58.3 HRC. The microstructure was transformed into austenite and graphite nodules through austenitization at 1050 °C for 6 h and water quenching with a hardness of 23.0 HRC. Tempering treatment effectively increased the hardness to 56.6 HRC due to the precipitation of carbides and phase transformation from austenite to martensite. [ABSTRACT FROM AUTHOR]

The failure mechanism of TP347H austenitic heat-resistant steel tube serviced in boiler superheater in a 600 MW subcritical thermal power unit is presented in this paper. Through microstructure observation, energy-dispersive spectrometry analysis, and selected electron diffraction, the mechanism of TP347H superheater bend tube failure is found to be attributed to intergranular corrosion cracking, more M23C6 and primary NbC(N) phase precipitating and coarsening along the grain boundary and formation of high content of slip lines and α′-martensite structure. The α′-martensite kept the Kurdjumov–Sachs (K-S) orientation relationships with parent austenite phase (γ-parent), which generated in TP347H bend tube may be related to the deformation-induced martensite (DIM) during rolling and cold working. The α′-martensite nucleated mainly at the grain boundary intersection between the twin crystal and γ-parent and grew inwards along the twin band. The dislocation density at the intersection is larger, and the secondary NbC(N) phase inhibited the nucleation of α'-martensite. [ABSTRACT FROM AUTHOR]

High strength press hardening steels have a broad perspective of application for automobile light-weight technique. However, they also face a huge challenge of hydrogen related mechanical degradation as atomic hydrogen intrudes into products during their production or in service. Two press hardening steels with different strengths were studied comparatively under the conditions of high hydrogen fugacity without external loading to evaluate their susceptibility to hydrogen embrittlement (HE). In combination with the microstructure characterization through TEM and EBSD, the results showed that these two steels display different surface hydrogen damage modes, e.g., hydrogen blistering for the steel with strength of 1000 MPa and hydrogen-assisted cracking for the steel with strength of 2000 MPa, although their damage sensitivity ratio largely obeys the tradeoff relation between the strength and HE susceptibility. Internal hydrogen pressure is a necessity for formation of hydrogen blisters because the pressure should provide a driving force for plastic deformation of blister surface, which indicates that the hydrogen blistering has some difference in HE mechanism compared to the hydrogen-assisted cracking. The main crack propagation mode is transgranular cracking for both steels, and the crack path concentrates on the {110} slip plane, especially along the block/lath boundaries, which is indicative of the inter-lath decohesion cracking. Therefore, it can be concluded that in the absence of applied loading the intra-variant boundaries have a higher HE susceptibility compared to the prior austenite grain boundaries. • Different surface damage modes (e.g., hydrogen blistering or cracking) occurred on their surface of two PHSs. • Inter-lath decohesion cracking along {110} slip plane is a common mode for crack propagation. • Plastic deformation of hydrogen blistering is controlled by internal hydrogen pressure. • Hydrogen cracking for the PHS2000 forms by a coupled mechanism of HESIV and HEDE. [ABSTRACT FROM AUTHOR]

The objective of the present investigation is to synthesise and characterise the Cu-Al-Ag shape memory alloys with minor Mn addition. Synthesis of Cu-Al-Ag-Mn SMA was done by induction furnace and gravity die casting, with constant Ag/Mn ratio (5% Ag and 2% Mn), the aluminium composition is varied from 8% to 14%. The as-cast sample will be further subjected to thermo-mechanical treatment to produce a sheet which exhibits shape memory effect. This study is to determine the influence of Al content on shape memory characteristics, microstructure, and phase transformation temperatures. The phase fraction of β'1 increased from 56% to 67% along with subsequent reduction of γ1' phase fraction from 23% to 17%, which is essential for improvement of shape memory properties with increase of aluminium constituent. X-ray diffraction revealed that the crystalline size decreased 79 to 32 nm and lattice strains increased from 0.24% to 0.69% with increase of Aluminium. With an increase in aluminium content, the martensite transformation temperature decreased from 386°C to 246°C, and the shape memory effect increased from 81 to 90% strain recovery. The ability to control shape memory characteristics by changing Al composition will improve the scope for this alloy in various shape memory applications. [ABSTRACT FROM AUTHOR]

The experimental discovery of four-layer orthorhombic (4O) martensite has added new research motivation to the Ni–Mn–Sn magnetic shape memory alloy. Herein, the martensitic transformation, magnetic properties, and electronic structures of Ni2Mn1+xSn1−x alloys are investigated using the first-principles calculations. The results show that the increasing Mn content destabilizes the stability of austenite (A) compared to the non-modulated (NM) martensite. This composition adjustment promotes the occurrence of martensitic transformation in the range of 0.375 ≤ x ≤ 0.75, and the corresponding phase transition sequence is A → 4O → NM during cooling. An intense hybridization bond exists between excess Mn and its surrounding atoms. The increasing antiferromagnetic interaction between excess Mn and normal Mn weakens each atomic moment and, thus, the total magnetic moment. Furthermore, the physical essence of the phase stability and magnetic properties variation with composition was explained based on the electronic density of states. [ABSTRACT FROM AUTHOR]

Cryogenic turning of metastable austenitic stainless steels can improve wear resistance of the resulting surface due to the phase transformation of γ‐austenite into α'‐ and/or ϵ‐martensite in the near surface layer. By using a cryogenic two‐step turning process, the amount of deformation‐induced α'‐martensite in the subsurface regime can be further increased. To determine the influence of the implemented and optimized two‐step turning strategy on the tribological properties of countersurfaces for radial shaft seals, an evaluation of wear behavior of the shaft seal countersurface as well as microstructural analyses in subsurface regime is presented and compared to the cryogenic single step turning process. The results show that not only the integral phase transformation in the overall subsurface region, but also the local phase distribution plays an important role when it comes to the surface performance in tribological applications. [ABSTRACT FROM AUTHOR]

The purpose of this study is to understand in detail the micromechanical behavior of martensite and ferrite microphases in a medium‐Si 35CHGSA dual‐phase (DP) steel by varying the martensite volume fractions (MVF) and ferrite phase constituents. Light microscopy combined with microhardness measurements is supplemented by field‐emission scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and X‐ray diffraction in order to evaluate the micromechanical behavior of martensite and ferrite microphases in relation to the evolving microstructure. The experimental observations illustrate that ferrite microhardness diminishes sharply from 352 to 217 HV5g with the change in ferrite volume fraction (FVF) from 3 to 13%, beyond which it increases abnormally to 245 HV5g with a further increase in VF to 15%. The martensite microhardness too varies significantly depending on the progress of ferrite formation in the intercritical range. The hardness drops with further increase in FVF as a result of longer holding times. These observations are rationalized in part to the mutual interaction of martensite with ferrite, and the variation of martensite and ferrite alloying concentrations, developed as a result of ferrite formation during intercritical holding at 720 °C. [ABSTRACT FROM AUTHOR]

Quenching and partitioning (QP) is a heat treatment that is designed to enhance both the mechanical properties and ductility of low‐ and medium‐carbon steels. This treatment is performed on steels with a tailored chemical composition. Herein, QP treatments are designed and performed on commercial low‐silicon 33MnCrB5 boron steel. Different temperatures (evaluated using thermodynamic simulations) and times are tested. Scanning electron microscopy investigations are conducted to observe the microstructure, whereas X‐ray diffraction and electron backscattered diffraction analyses are performed to assess the presence and amount of retained austenite (RA). Tensile tests are performed to investigate the mechanical properties. The designed treatments introduce a fraction of up to 4.6% of RA in the final microstructure. Tensile tests show that the QP samples are characterized by high ultimate tensile strength (1633–1756 MPa) with an increased elongation at break with respect to the reference quenching and tempering condition (16–18% versus 9%). Hardening coefficients are linked to martensite tempering in the initial stages of plastic deformation, whereas at higher strains, they are mostly influenced by RA presence. The proposed treatments are successfully performed on 33MnCrB5 grade, leading to a set of tensile properties that are not exploitable with traditional treatments. [ABSTRACT FROM AUTHOR]

An air‐cooled low‐carbon Mn–Si–Cr alloyed steel with multiphase microstructure of carbide‐free bainite/martensite (CFB/M) is developed. The kinetics of bainitic transformation during air‐cooling process is discussed via considering the transformation latent heat with help of the measured temperature‐cooling curves. Results show that the CFB formed during air cooling can effectively refine the multiphase microstructure and stabilize the film‐like retained austenite that contributes to transformation‐induced plasticity effect upon deformation. An optimum combination of strength, ductility, and toughness of the air‐cooled bainitic steel is achieved (tensile strength: 1418 MPa, total elongation: 15.8%, and Charpy V‐notch impact energy: ≈71 J). The newly developed Mn–Si–Cr alloyed air‐cooled bainitic steel exhibits superior mechanical properties to the commercial 23CrNi3Mo steel but has a much lower alloy cost. [ABSTRACT FROM AUTHOR]

The evolution of the microstructure and the mechanical properties of a 15-6 martensite precipitated hardened (15-6 PH) stainless steel after thermal treatment and long-term aging at 480 °C were investigated. Compared with 17-4 PH steel, the content of Cr decreased and Ni increased in the newly developed 15-6 PH steel; therefore, reversed austenite formed after thermal treatment at 620 °C of the solution-treated 15-6 PH steel. Although the reversed austenite may reduce the strength of the steel, it is very beneficial for the inhibition of the aging brittleness of the steel. During the accelerated thermal aging at 480 °C, the Cu-rich phase gradually coarsened, and its crystal structure changed, while the reversed austenite phase sightly increased and the Charpy impact energy maintained a rather high value. The increase of the reversed austenite content can offset the reduction of the strengthening effect of the Cu-rich phase and therefore maintain an excellent impact property of the material after thermal aging. [ABSTRACT FROM AUTHOR]

A novel low-alloy ultrahigh-strength steel featuring excellent mechanical properties and comprising a nanolath structure was fabricated in this work using a quenching–partitioning–tempering (Q-P-T) process. The Q-P-T process comprised direct quenching and an isothermal bainitic transformation for partitioning after thermo-mechanical control processing (online Q&P) and offline tempering (reheating and tempering). The ultrafine nanolath martensite/bainite mixed structure, combined with residual austenite in the form of a thin film between the nanolaths, was formed, thereby conferring excellent mechanical properties to the steel structures. After the Q-P-T process, the yield and tensile strengths of the steels reached 1450 MPa and 1726 MPa, respectively. Furthermore, the Brinell hardness and elongation rate were 543 HB and 11.5%, respectively, with an average impact energy of 20 J at room temperature. [ABSTRACT FROM AUTHOR]

The influence of varying the manganese (Mn) contents of high-strength copper-containing hull steel on its microstructural evolution and mechanical properties was investigated. With increasing Mn content from 2 to 5%, the tensile strength of the steel increased by ~100 MPa, while the elongation of steel remained at ~23.5%, indicating good plasticity. However, the 2Mn sample had 128 J higher low-temperature (−84 °C) impact work than the 5Mn sample. The microstructures of different Mn steels were composed of fresh martensite (FM), ferrite/tempered martensite (F/TM), and reversed austenite (RA). The increase in Mn content markedly increased the presence of RA and intensified the work hardening caused by the transformation-induced plasticity (TRIP) effect during the tensile process. However, as the phase transformation in different Mn steels occurred in the early stage of strain and did not extend throughout the entire plastic deformation process, increasing plasticity via phase transformation was difficult. In addition, although the volume fraction of RA increased significantly in 4Mn and 5Mn steels, the stability of RA significantly decreased. The presence of numerous metastable blocks and coarse lath-like RA contributed little to low-temperature impact work and was even detrimental to toughness. The substantial fresh martensite resulting from phase transformation facilitated microcrack generation, owing to rapid volume expansion and mutual impacts, thus reducing the work required for crack formation. Additionally, the abundance of deformation twins significantly reduced the work needed for crack propagation. These combined actions significantly reduced the low-temperature toughness of 4Mn and 5Mn steels. [ABSTRACT FROM AUTHOR]

Two chromium-rich carbide hard-faced plates, alloy—A and alloy—B, were subjected to a 3-body dry sand abrasion test. The difference was in the coating microstructure. Alloy-A contains globular chromium carbide (M7C3 type) in the austenite matrix, whereas alloy—B is composed of a banded structure with an alternate layer of carbide and austenite. Alloy B showed a superior abrasion resistance (nearly 40%) than alloy—A. A detailed microstructural investigation was made on the abraded surface. The higher abrasive wear resistance of alloy-B was attributed to the coating morphology, the composite-like microstructure resulted in an effective strain distribution among the austenite matrix and carbides. This postulate was supplemented by higher average misorientation, which was observed at sub-surface regions of the worn-out specimen, leading to form a strain-induced martensite. However, in alloy—A, the abraded surface contained abundant broken carbides. [ABSTRACT FROM AUTHOR]

The effect of different microstructural factors on crack growth and fatigue fracture mechanisms in dual‐phase (DP) steels has yet to be fully understood. The present research examines the relationship between crack growth, microstructure, and fracture mechanisms. The samples were intercritically annealed at different temperatures to produce three different martensite volume fractions (MVFs). The results show that the mechanical incompatibility of ferrite and martensite promotes continuous crack tip deflection. MVF increases are associated with elevated fracture tortuosity, more significant fracture energy surface formation, and higher Paris law exponent m values. The interaction of the microstructure with the crack tip, the strain energy density, and the softening caused by secondary microcrack propagation are all illustrated by Electron backscatter diffraction (EBSD) maps. Increasing MVF promotes slow crack growth and a fracture energy increase of 22.9% between the as‐received and heat‐treated steels. Highlights: Martensite content in dual‐phase steels generate greater crack propagation resistance.Martensite volume increase produces a more significant number and extension of secondary microcracks.Differences in ferrite and martensite phases promote continuous crack tip deflection. [ABSTRACT FROM AUTHOR]

Fe-based superelastic alloys, which show both superelasticity and high damping capacity, can be divided into four alloy systems based on the characteristics of the martensite transformation that is responsible for these effects, viz., Fe-Pt, Fe-Pd, Fe-Mn-Si, and Fe-Ni-Co. Since 2010, Fe-Ni-Co-Al-based alloys that exhibit a large superelastic effect have attracted widespread attention. In this paper, the characteristics of the phase transformation from austenite ( γ ) to martensite ( α ') and the effects of the martensite variants in Fe-Ni-Co-Al-based superelastic alloys are summarized. The effects of alloying elements, precipitates and texture on the thermoelastic martensite transformation and the superelastic properties are reviewed. The factors affecting the superelastic effect and recoverable strain along with the related mechanisms are discussed. In addition, research progress on the damping performance, microwire structures, and modeling of Fe-Ni-Co-Al-based superelastic alloys are outlined. Finally, the challenges and future developments of the superelastic effect in Fe-Ni-Co-Al-based alloy are explored. [ABSTRACT FROM AUTHOR]

An overview of the most used variants of the structural-chemical Schaeffler diagram developed by various researchers is presented. A new version of the Schaeffler diagram and equations for calculating Cr- and Ni-equivalents are suggested, which makes it possible to correctly predict the content of δ-ferrite in the structure of heat-resistant ferritic–martensitic steels of the EP450 – EP823 – EK181 – ChS139 group containing ≥ 10 wt.% Cr, after hot deformation and heat treatment. Based on the factor analysis of the relationship between the physicochemical and structural characteristics of such steels and their mechanical properties, equations are obtained in which the Cr- and Ni-equivalents are allowed for as factors determining the value of the yield strength. [ABSTRACT FROM AUTHOR]

The probability of martensitic transformation in stable 316L austenitic steel obtained using a 3D laser printer is investigated. Compressive deformation of the studied samples was carried out at room temperature at a high rate (2 × 10–2 sec–1). The features of the martensitic transition and the conditions for formation of an intermediate phase of epsilon-martensite are considered. [ABSTRACT FROM AUTHOR]

[Display omitted] Lunar soil preserves numerous fragments of meteorites impacting on the Moon, providing a unique opportunity to investigate the distribution of the types of projectiles over billions of years. Here we report the first discovery of an iron meteorite fragment from the Chang'e-5 lunar soil, which consists mainly of martensite (quenched from taenite), kamacite, and schreibersite, with a trace of pentlandite. The meteorite fragment is Ni- and P-rich, S-poor, and based on its mineral chemistry and bulk composition, can be classified into the IID-group, a rare and carbonaceous group of iron meteorite originating in the outer Solar System. This meteorite fragment experienced only limited partial melting followed by fast cooling, suggestive of efficient preservation of intact remnants of iron meteorites impacting on the porous lunar regolith. Alternatively, it is a relic of a low-velocity impact of submillimeter-sized metal grains originated from an IID-like iron meteorite. Our observations demonstrate that it is feasible to achieve the type distribution of meteorites impacting on the Moon via systematically analyzing a large number of metal grains separated from lunar soils, thus shedding light on the dynamic evolution of the Solar System. [ABSTRACT FROM AUTHOR]

This study, through experimental analysis and numerical calculations, not only identifies the critical cooling rate for eliminating banded structures in 20CrMnTi gear steel but also analyzes the impact of cooling rate on banded structures, including the mechanisms related to element distribution and interface migration. The results indicate that the fundamental cause of banded structure formation is the presence of chemical segregation bands, and increasing the cooling rate leads to a reduction in the grade of ferrite/pearlite banded structures, with a critical cooling rate of 0.55 °C s−1. Bainite and martensite banded structures are observed in samples cooled at rates of 3 and 5.8 °C s−1, respectively. As the cooling rate increases from 0.07 to 1 °C s−1. The ferrite phase transformation time in the solute‐poor zone is shortened from 171 to 12 s within the ferrite phase transformation temperature difference (ΔAr3$A_{\text{r} 3}$) between the poor and rich solute zones. The concentration difference of carbon (C) on both sides of the α/γ phase interface increases from 0.350 mass% to 0.431 mass%, and the diffusion distance of C decreases from 34.38 to 7.57 μm. When the diffusion distance of C is less than half of the width of the solute‐rich banding (12.5 μm), the ferrite banded structure disappears. [ABSTRACT FROM AUTHOR]

Fe‐based filler material with a composition of Fe–20Ni–5Co–2.5Mn–0.2C is developed for welding 9% Ni steel. To ensure high weldability through compositional similarity, the composition of the Fe‐based filler material is designed based on that of 9% Ni steel. The filler material has elements such as Ni, Mn, Co, and C to enhance its compatibility with the 9% Ni steel. The Fe‐based filler material is designed to control the martensite formation temperature, resulting in the appearance of the martensite–austenite dual phase during rapid cooling. The weld joint shows a distinct microstructure characterized by the presence of austenite‐covered packet lath martensite. The mechanical properties of the weld joint are investigated via Vickers harness and tensile tests at 25 and −163 °C. In comparison to 9% Ni steel, the weld joint prepared using the Fe‐based filler material exhibits yield and tensile strengths that are ≈5.5% higher. Additionally, the tensile fracture of the specimen occurs exclusively within the base metal, without any involvement of the weld metal or heat‐affected zone. Further, the fracture surface is observed. In the findings of this study, the applicability of the Fe‐based filler material for welding 9% Ni steel is demonstrated. [ABSTRACT FROM AUTHOR]

In this study, a desirable combination of strength, ductility, and toughness in low-carbon 30CrMnSiA steel is achieved by a hierarchical multiphase microstructural architecture subjected to one- and two-step quenching and partitioning (Q&P) processes. The microstructural constituents are studied by EBSD, x-ray diffraction, dilatometry, and TEM. Experimental results show that microstructural refinement occurs in the martensite and bainite at a lower quenching temperature, where more Bain groups form in one close-packed plane group. This causes random distribution between martensite and bainite blocks, enlarging the volume of high-angle grain boundaries. Such refined microstructure, particularly for the increased martensite with higher-density dislocations, causes an increased strength at a decreased quenching temperature. By comparison, increased quenching and partitioning temperature produces more stable film-like retained austenite (RA) and a low dislocation density in martensite/bainite (M/B); thus, it provides better deformation by accommodating with M/B laths and absorbing substantial energy due to the transformation-induced plasticity effect. The lower dislocation density, the higher volume fraction of RA, and the higher HAGBs improve the impact toughness and tensile properties of lean alloy steel through a moderate Q&P process. [ABSTRACT FROM AUTHOR]

In order to obtain the good match between yield strength and low-temperature toughness, the short-time partial austenitization (SPA) process was employed for V/Mo-bearing 0.22C–5.24Mn steel. The initial microstructure after intercritical tempering was dual-phase ferrite and reversed austenite (RA), while the final microstructure consisted of ferrite, RA, and secondary martensite (SM) after being subjected to the SPA process. (V, Mo)C with disclike morphology mainly precipitated during intercritical tempering, and the aspect ratio of particles decreased, leading to the appearance of near-spherical morphology. After being subjected to SPA process, the resultant multiphase hierarchical microstructure (three layers: outer layer of ferrite, interlayer of SM, and inner layer of RA) enabled a high yield strength of 1097 MPa, a total elongation of 14%, and an impressive impact energy of 33.3 J at −20 °C. The strengthening contribution of (V, Mo)C precipitation was estimated to be about 108 MPa. [ABSTRACT FROM AUTHOR]

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels. [ABSTRACT FROM AUTHOR]

The paper presents results of transmission electron microscopy of the plasma coating/substrate interface. Its elemental and phase compositions and defect substructure are investigated. The high-speed steel R18-Yu coating is deposited in argon medium onto the type 30HGSA steel substrate high-tempered for several times. It is shown that both the coating and substrate are mutually alloyed. Primarily the substrate demonstrates a multi-phase, multi-element sub-nanoclystalline structure with the lamellar morphology. It is shown that multiple high-temperature tempering leads to the formation of carbide nanoparticles both in the volume and at the boundaries of the martensite lath structure. [ABSTRACT FROM AUTHOR]

The first stage of the surface martensite formation with a habit plane close to {12 14 17} is interpreted in terms of the dynamic theory of martensitic transformations. Based on the analysis of the elastic field calculations, the dislocation centers of crystal nucleation are identified. The principal role is attributed to the dislocation loop segments oriented along the <12 1> directions. [ABSTRACT FROM AUTHOR]

Soil‐working tools in agriculture are made of boron‐containing steels with high wear resistance and hardenability. Nevertheless, these tools are subject to high impacts, abrasive wear, and fatigue and are therefore prone to failure. To combine varying levels of properties within one component in as‐quenched condition can be beneficial for such products. To obtain this property variation, a component must undergo a complex and controllable cooling. Therefore, the aim of this work is to obtain a microstructure gradient along two 15 mm‐thick steel plates in a newly developed test rig by water jet impingement technique to confirm its controllability and flexibility. Furthermore, a quenching simulation model is created for hardness prediction using phase transformation data from a machine learning tool. Microstructure variation is observed using light optical microscopy and the electron backscatter diffraction technique. Mechanical properties are studied through tensile tests and hardness measurements and are also compared with simulation results. The 0.27 mass% C steel sample is obtained in almost fully martensitic state transitioning to a softer ferritic/bainitic condition, while the 0.38 mass% C steel sample results predominantly into a fully hardened martensitic state and slightly shows ferritic and bainitic features along the sample. The quenching simulation model shows promising hardness prediction for both steels. [ABSTRACT FROM AUTHOR]

Temper embrittlement is a major challenge encountered during the heat treatment of high-performance steels for large forgings. This study investigates the microstructural evolution and mechanical properties of Cr-Ni-Mo-V thick-walled steel, designed for large forgings with a tensile strength of 1500 MPa, under different tempering cooling rates. Optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to analyze the microstructural features. The results demonstrate that the embrittlement occurring during air cooling after tempering is attributed to the concentration of impurities near Fe3C at the grain boundaries. The low-temperature impact toughness at −40 °C after water quenching reaches 29 J due to the accelerated cooling rate during tempering, which slows down the diffusion of impurity elements towards the grain boundaries, resulting in a reduced concentration and dislocation density and an increased stability of the grain boundaries, thereby enhancing toughness. The bainite content decreases and the interface between martensite and bainite undergoes changes after water quenching during tempering. These alterations influence the crack propagation direction within the two-phase microstructure, further modifying the toughness. These findings contribute to the understanding of temper embrittlement and provide valuable guidance for optimizing heat treatment processes to enhance the performance of high-performance steels in large forgings. [ABSTRACT FROM AUTHOR]

Fe-Mn-Si shape memory alloys (SMAs) have gained significant attention due to their unique characteristics. However, there remains a gap in the literature regarding the fabrication of these alloys using laser-directed energy deposition (LDED). This study fills this void, investigating the properties of Fe-Mn-Si SMAs produced by LDED. The shape memory performance of as-deposited Fe-Mn-Si SMAs was studied using a tensile method. Alloys underwent different degrees of deformation to assess their shape memory effect. Microstructural evaluations were conducted post-deformation to observe the internal structures of the alloys. The tensile tests revealed that shape recovery rates for deformation levels of 3%, 7%, 11%, and 15% were 68.1%, 44.2%, 31.7%, and 17.6%, respectively. Notably, the maximum recoverable deformation of the LDED-formed Fe-Mn-Si-based shape memory alloy reached 3.49%, surpassing the traditional deformation processing SMAs (<3%). The presence of a significant number of stacking faults was linked to the enhanced shape memory performance. The LDED technique demonstrates promising potential for the fabrication of Fe-Mn-Si SMAs, producing alloys with enhanced shape memory performance compared to traditionally processed SMAs. The study's findings offer new insights and broaden the applicability of LDED in the field of SMAs. [ABSTRACT FROM AUTHOR]

This research project was focused on understanding the production and response to heat treatment for a Fe8Mn2Al2Si0.3C steel alloy. These alloys can be heat treated to produce multiphase microstructures containing ferrite, austenite, martensite, and/or iron carbide. A previous project examined "high" carbon contents (0.5 wt% and 0.75 wt%), where the microstructure consisted primarily of stabilized austenite and heat treatment could produce austenite plus ferrite dual-phase microstructures that had higher hardness and, presumably, higher tensile strength (Druschitz in Inter Metalcast, 2023. https://doi.org/10.1007/s40962-023-01000-1). In this study, we examined a "low" carbon content (0.3 wt%), where the microstructure was primarily martensite and heat treatment could produce martensite plus ferrite and/or austenite. Therefore, this lower carbon content Fe8Mn2Al2Si0.3C steel had higher hardness (and presumably greater strength) compared to the higher carbon content steels. [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]