Martensite Regions Research Articles

Microstructure Evolution and Tensile Properties of Medium Manganese Steel Heat Treated by Two-Step Annealing

In this paper, the nucleation and growth of austenite are controlled through a two-step annealing process to achieve multi-scale distribution and content increase of retained austenite in low manganese series medium-Mn steel. Combining SEM, EBSD, AES, and other experimental equipment, the evolution rules of the microstructure, properties, and element distribution behavior of the test steel during the annealing process are studied. Compared with one-step annealing, the two-step annealing significantly broadens the size distribution range of retained austenite. In the first step, after annealing at a higher intercritical temperature (760 °C), the ferrite and the M/A island are obtained, completing the initial partition of Mn and the refinement of microstructures. During the second step of annealing (720 °C), the primary Mn-rich martensite region provides higher nucleation driving force and finer dispersed nucleation sites, promoting the nucleation and growth of reverse transformation austenite. At the same time, the metastable-retained austenite formed after the first step of annealing continues to grow through interface movement. Furthermore, a high proportion (23.4%) of retained austenite with multi-scale distribution is formed in the final microstructure, and the product of strength and elongation increased from 21.8 GPa·% by the one-step annealing process to 30.1 GPa·%.

Temperature Effect on Deformation Mechanisms and Mechanical Properties of Welded High-Mn Steels for Cryogenic Applications.

High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that can lead to the formation of deformation twins or transform to ε-martensite or α'-martensite as the temperature decreases. In this study, submerged arc welding (SAW) was applied to fabricate thick pipes for cryogenic industry applications, but it may cause problems such as an uneven distribution of manganese (Mn) and a large weldment. To address these issues, post-weld heat treatment (PWHT) is performed to achieve a homogeneous microstructure, enhance mechanical properties, and reduce residual stress. It was found that the difference in Mn content between the dendrite and interdendritic regions was reduced after PWHT, and the SFE was calculated. At cryogenic temperatures, the SFE decreased below 20 mJ/m2, indicating the martensitic transformation region. Furthermore, an examination of the deformation behavior of welded high-Mn steels was conducted. This study revealed that the tensile deformed, as-welded specimens exhibited ε and α'-martensite transformations at cryogenic temperatures. However, the heat-treated specimens did not undergo α'-martensite transformations. Moreover, regardless of whether the specimens were subjected to Charpy impact deformation before or after heat treatment, ε and α'-martensite transformations did not occur.

Tensile mechanical behavior of functionally graded NiTi alloy manufactured via laser powder bed fusion

Laser powder bed fusion (LPBF) offers the potential to modify the characteristics of NiTi alloys, allowing for the creation of bespoke solutions tailored to specific applications. In this study, four functionally graded NiTi alloys with varying martensite/austenite distributions were designed and manufactured. A comprehensive investigation was conducted into the local microstructure, phase transformation behaviour, and tensile mechanical behaviour. The findings illustrate that, in comparison to homogeneous NiTi, gradient NiTi displays a propensity for preferential deformation within the martensitic region, attributable to the presence of localised performance variations. Gradient NiTi exhibits evident strain hardening and a wider range of plateau stress due to its intricate step-by-step phase transformation behaviour. The strain gradient strengthening near the interface between martensite and austenite endows gradient NiTi with enhanced fracture strength. Furthermore, while ensuring a discernible gradient in strain, the design of the interface with narrow spacing and parallel to the tensile direction can effectively enhance the mechanical properties of gradient NiTi. This study validates that gradient design based on LPBF is an effective approach for controlling the macroscopic mechanical behavior of NiTi alloy.

Phase transformation mechanisms occurring during spark plasma sintering elaboration of new duplex composite stainless steels

This study focuses on the elaboration of duplex stainless steels (DSS) from powder mixtures using spark plasma sintering (SPS). Different mass fractions of an austenitic 316L powder and a ferritic 410L one were blended and then sintered by SPS. Microstructural characterizations of the sintered samples obtained from different powder mixtures were performed. They were coupled with marking experiments of the powder particles’ surface. The results showed the formation of martensite within the ferritic powder and at the austenite/ferrite interfaces, following two different mechanisms. In addition, it was found that the width of the martensitic regions is mainly influenced by the diffusion of Cr and Ni from the austenitic to the ferritic powder during sintering. The characterizations revealed that the originality of this approach lies in the particular microstructure obtained after sintering. The characteristic size of the ferritic and austenitic domains in the final material is that of the initial powder particles (up to some hundred microns). Moreover, each domain is formed by equiaxed and isotropic grains, having a size ranging from some microns to some tens of microns. This particular microstructure justifies the use of the term “composite duplex stainless steels” (COMPLEX) for this kind of new DSS.

Effects of annealing temperature on microstructure and mechanical properties of a low density δ-TRIP steel plate via intercritical quenching-annealing process

In this study, the effects of annealing temperature on microstructure and mechanical properties of Fe–9Mn–5Al-0.3C (wt.%) low density steel plates via intercritical quenching-annealing process were investigated through field-emission scanning electron microscopy, electron backscatter diffraction, X-ray diffraction, and tensile tests. The results showed that the experimental steel maintained micro-laminated microstructure after intercritical quenching-annealing treatment, consisting of δ-ferrite band and tempered martensite lamellar. After annealing at the range of 600–800 °C following quenching of 1050 °C, tempered martensite lamellar mainly changed, and affected the mechanical properties of the steel. The annealed experimental steels exhibited wide yield strength grades (460–620 MPa) with excellent ductility (40–63 %) and low yield-tensile ratio (0.65–0.75). The proportion of austenite, the density of geometrically necessary dislocations, and high-angle grain boundary density of tempered martensite region, as well as the presence or absence of carbides, were considered to contributed to the mechanical properties. Austenitic mechanical ability was analyzed. Various annealed temperature led to the different levels of austenitic stability through changing the enrichment of alloyed elements in austenite, further causing different degrees of TRIP effect. TWIP effect existed during deformation according to estimation of SFE. The steel annealed at 740 °C had maximum uniform elongation (62.4 %) and the highest product of strength and elongation (45.2 GPa%), depending on the maximum proportion of austenite transformed into martensite during deformation. However, the 680 °C annealed steel with the highest austenitic stability exhibited deficient TRIP effect, leading to the occurrence of necking. Moreover, work hardening behavior and fracture morphology of the experimental steel were analyzed.

A physics-based plasticity study of the mechanism of inhomogeneous strain evolution in dual phase 600 steel

In this study, we employ a physics-based crystal plasticity finite element method (CPFEM) approach to study the microstructural response of DP600 steel to various loading types. With the pursued approach, it is possible link microstructural changes in the dual phase (DP) steel to its macroscopic response in a convenient and efficient manner. Microstructural data were acquired first from experimental work via the electron backscattered diffraction (EBSD) method. DP crystallographic features were then fed to a numerical hybrid calculation subroutine combining a comprehensive physics-based crystal plasticity scheme for ferrite along with an isotropic plasticity scheme for martensite defined on a single-layer representative volume element (RVE). The developed single-layer 3D mode, while allowing for high computational efficiency, can capture the stress/strain distribution, revealing the microscopic features of the deformation process including the physical evolution of the dislocation density, retexturing, and morphology. The single-layer RVE physics-based method employed herein establishes the strong correlation between morphology, dislocation density and deformation response of the material under various loading types. Specifically, findings reveal that the tendency of the ferrite phase neighboring the martensite regions in the DP steel to retexture is much more profound than pure ferrite when subjected to the same loading conditions, pointing out to the steep strain gradients in the former component. Martensite phase facilitates considerable heterogeneity in the stress and strain distribution, increases the misorientation polarization as well as leading to local strain hardening in the neighboring ferrite volume that stem from profound increase in spatial dislocation density. Stress-strain curves under various loading schemes are simulated and discussed in the light of the experimental findings in literature, revealing the dependence of the microstructural evolution on the loading type.

CARBURIZING-QUENCHING HARDNESS MODEL ANALYSIS AND COMPARISON

Unlike the conventional calculation models of the hardness, a carburizing-quenching hardness model considers the influence of the carbon content on the phase transformation and hardness. The volume fraction model (VFM) and Jominy curve model (JCM) for calculating carburizing-quenching hardness of 20CrNi2Mo steel were built in this study, and the models were used to calculate the hardness of Jominy and gear samples. The hardness results of both models were compared, and the simulation results were verified with the corresponding test results. The results show that the hardness values obtained with both models have a certain calculation accuracy. But due to considering the influence of residual austenite (RA) on the hardness, the simulation accuracy of the VFM was better for the low Jominy distance and the hardened case, while the simulation accuracy of the JCM was better for the large Jominy distance and the low-carbon martensite region; the calculation of the latter is more convenient and its accumulated error is small.

Исследование превращений переохлажденного аустенита при ступенчатой закалке стали 20Cr2Mn2SiNiMo

Currently, step quenching of steels in the temperature range of martensitic transformation, including quenching – partitioning, has found wide application in the automotive industry. Step quenching technology is successfully used to increase a set of properties, which most often include temporary tensile strength and relative elongation. The authors carried out a dilatometric study of the supercooled austenite transformations occurring in the 20Cr2Mn2SiNiMo steel, when implementing various options of step quenching with holding in the martensitic region. It was found that after single-stage quenching, single-stage quenching followed by tempering, and two-stage quenching, primary martensite, isothermal bainite, and secondary martensite are formed in various quantitative ratios. Using X-ray diffraction phase analysis, the amount of residual austenite was determined during step quenching. It has been shown that two-stage quenching makes it possible to stabilise up to 14 % of residual austenite, in the structure of the studied steel, at room temperature. Research has revealed that 20Cr2Mn2SiNiMo steel is characterised by a decrease in the crystal lattice parameter of the residual austenite, with an increase in its content in the steel structure. Uniaxial tensile and impact bending tests were carried out, and the values of the mechanical properties were determined. It has been found that during two-stage quenching, higher strength and elongation values, with lower values of relative contraction and impact strength are achieved compared to oil quenching and low-temperature tempering. The study showed that, with regard to the structural reliability of machine-building parts, step quenching is not the optimal heat treatment mode for the steel under study. The best combination of strength, ductility and impact hardness is achieved after quenching and low-temperature tempering.

Modeling a sample size-dependency of martensitic phase transformation using a mesoscale framework

Predicting a sample size-dependency of the constitutive response of any material system when it is being used in nano- and micro-scale devices, such as NEMS and MEMS, is very crucial for their design process. This also includes the shape memory alloys (SMAs), where predicting a sample size-dependency of the phase transformation process is the key aspect. Many experimental studies with micropillar compression tests showed an increase in critical stress to transformation and an increase in transformation hardening as the sample size decreases below a critical size. In this work, we have employed and extended a recently developed mesoscale framework to model such size effects in SMAs. A plane strain tensile SMA strip of finite width is analyzed within a small deformation framework. The martensitic transformation regions are modeled as Eshelby inclusions in an austenite phase matrix. Circular potential nucleation sites are considered with a square packing for their spatial locations and with nucleation stress assigned to each site from a Gaussian distribution. The combination of the Gaussian distribution of nucleation stress and the size of the nucleation site represents the underlying SMA material microstructure. Our numerical analysis, with varying values of the aspect ratio between the strip width and the nucleation site size, provides a critical value of the aspect ratio characterizing a transitioning length scale between a bulk vs. a sample size-dependent phase transformation behavior. At the transition, the critical stress to phase transformation and the transformation hardening increase drastically as the aspect ratio decreases below its critical value. The limitations of these predictions are discussed with existing literature on experimental observations, and some perspectives to improve the model are stated.

Characterization of dry-sliding wear phenomena in a novel martensitic structure based low-carbon Nb and V alloyed steel

The current study investigated unlubricated dry-sliding wear behaviour of a low-carbon Nb+V stabilized microalloyed steel in various treated states, i.e., as-received, direct-quenched (DQ, martensitic-structure) and tempered (T500) samples. The effects of applied normal load on specific wear-rate, worn-surface and sub-surface characteristics have been discussed, enlightening relevant deformation mechanisms. The specific wear-rate is found to be the lowest (2.91 ×10−5 mm3m−1N−1) for the DQ specimen, primarily due to its better combination of hardness, strength, and toughness. SEM investigation of worn-surfaces confirmed that abrasion (i.e., micro-cutting and ploughing) and oxidative wear mechanisms are the dominant phenomena in all the samples, while the counter-face material remained unchanged. The sub-surface analysis indicates the severely deformed region and bending of martensite is only 1–2 µm and 7 µm for the DQ sample, whereas increases to 3–5 µm and 15 µm, respectively, in the T500 specimen.

Study of fusion boundary microstructure and local mismatch of SA508/alloy 52 dissimilar metal weld with buttering

A SA508/Alloy 52 dissimilar metal weld (DMW) mock-up with double-sided Alloy 52 butterings, which is fully representative of Ringhals pressurizer surge nozzle DMW repair solution, was studied. The microstructure, crystal structure, elemental diffusion, carbide formation and macro-, micro- and nano-hardness of the SA508/nickel-base Alloy 52 buttering fusion boundary (FB) were investigated. Three types of FBs were analyzed, i.e., narrow FB (∼80–85% of whole FB), tempered martensitic transition region (∼15%) and wide partially mixed zone (∼1–2%). The different FB types were induced by the local heat flow and respective elementary diffusion, which significantly influence the local hardness mismatch across the DMW interface and the local brittle fracture behavior.

Effect of Carbon Partitioning on Abnormal Martensite Hardening in a Conventional Quench and Temper Medium Silicon Low Alloy Steel under Ferrite-Martensite Dual-Phase Microstructure

Abstract The purpose of this research work was to investigate the effect of carbon partitioning within ferrite and prior austenite (martensite) during progress of ferrite formation and consequently its relation to the associated martensite hardening in a medium silicon low alloy conventional quench and temper steel. For this aim, several ferrite-martensite dual-phase (DP) samples containing various volume fractions of ferrite and martensite microphases were developed. The X-ray diffraction and electron microscopy with spot and line-scan X-ray energy-dispersive spectroscopy (EDS) for carbon analysis were used in conjunction with light microscopy and hardness test to follow the variation of carbon partitioning within ferrite and prior austenite (martensite) regions and consequently the associated martensite hardening in the DP samples.

In-situ micro-cantilever bending studies of a white etching layer thermally induced on rail wheels

A complex and untraceable mechanical and thermal loading situation in rolling-sliding contacts can lead to the formation of white etching layers (WELs), depicting critical crack initiation sites. For our detailed studies, to obtain a holistic view of the microstructural characteristics and micro-mechanical properties, we prepared a WEL on a decommissioned (after 200,000 km service life) rail wheel by laser surface treatments with a defined energy input. This WEL is predominantly martensitic down to a depth of 30–40 μm, after which a transition to the deformed ferritic-pearlitic microstructure of the hypoeutectoid rail wheel steel is present. The martensitic region is with 6.98 ± 0.68 GPa significantly harder than the transition zone (5.17 ± 0.39 GPa) and the deformed ferritic-pearlitic base material (3.30 ± 0.33 GPa). In-situ V-notched micro-cantilever bending experiments of the martensitic (and thus most brittle) region show crack initiation and propagation – mostly along the boundaries of the martensitic grains – besides a plastic behavior. Applying the elastoplastic fracture mechanics allows to derive the local fracture toughness KIQ, which is 16.4 ± 1.2 MPam1/2 for this martensitic region of the WEL. The results outpoint the application of micro-cantilever bending tests in addition to hardness testing as a promising tool to discuss the relationship of microstructural characteristics with its micro-mechanical properties.

Roles of pre-formed martensite in deformation behavior and strain partitioning of medium-carbon bainitic steel by quasi-in-situ tensile tests

Microstructural features play a major role in strain distribution and TRIP effect, influencing the plastic deformation behavior of multiphase steel. In this work, the bainitic multiphase microstructure with or without pre-formed martensite (PM) was obtained by the below-MS and above-MS austempering process. The evolution of strain partitioning and TRIP effect on plastic deformation were studied by combining micro digital image correlation (μ-DIC) analysis with in-situ tensile test in the multiphase microstructure. The changes of microstructure during deformation were systematically investigated by various characterization methods. The results show that the regions of strong strain partitioning in multiphase microstructure are different. Compared with the above-MS austempered sample without PM, the strain partitioning of the below-MS austempered sample containing PM is concentrated in the pre-formed martensite region while not in the blocky retained austenite (RA) region. The strain concentration in the PM region of the below-MS austempered sample is smaller than that in the blocky RA region of the above-MS austempered sample at the same engineering strain. The PM shares the stress load on RA during plastic deformation, thus can coordinate microstructure deformation and delay the early occurrence of the TRIP effect of the below-MS austempered sample. Moreover, the introduction of PM in the below-MS austempered sample increases the mechanical stability of RA, which is beneficial to produce an effective TRIP effect and delay necking to high strain. Consequently, the plasticity of the medium-carbon bainitic multiphase steel containing PM is enhanced by the effective TRIP effect and uniform strain partitioning.

Simulation and Microstructure Prediction of Resistance Spot Welding of Stainless Steel to Carbon Steel

Joining of stainless steel to carbon steel is widely used in various industries. Resistance spot welding (RSW) is a suitable process for joining steel sheets. Due to the complexity and importance of optimizing the parameters, numerical simulation of this process was considered. In this research, the electrical-thermal-mechanical simulation of RSW of 304 stainless steel to St37 carbon steel was performed using finite element method (FEM). Then, the simulated weld nugget size was compared with the experimental results of optical microscopy (OM). In addition, diffusion of metallic elements of the steels in the molten region was simulated using Fick’s equation and compared with experimental results of energy-dispersive X-ray spectroscopy (EDS). It was shown that diffusion of Cr and Ni through the weld nugget, would make a new stainless steel structure. Microstructure prediction of the heat affected zone (HAZ) was performed using Koistinen–Marburger and Leblond–Devaux equations to predict the percentage of martensite and ferrite-perlite phases during the heating and cooling stages of the specimens from room temperature to the peak temperature and cooling down under the Mf temperature. The results of this simulation were validated by scanning electron microscopy (SEM) images and shear tensile and micro-hardness test results. The simulation results showed that increasing the heat input from 1250 A during 0.5 s to 3750 A during 1.5 s, increases the percentage of martensite, from 40% to 80%, in the HAZ and widens the martensite region.

Automated Methodology for Volume Fraction Measurement of Three Phase Steel Micrograph Using Image Processing Techniques

A quantitative description of microstructure governs the characteristics of the material. Various heat and excellent treatments reveal micro-structures when the material is prepared. Depending on the microstructure, mechanical properties like hardness, ductility, strength, toughness, corrosion resistance, etc., also vary. Microstructures are characterized by morphological features like volume fraction of different phases, particle size, etc. Relative volume fractions of the phases must be known to correlate with the mechanical properties. In this work, using image processing techniques, an automated scheme was presented to calculate relative volume fractions of the phases, namely Ferrite, Martensite, and Bainite, present in the microscopic image of high strength low alloy steel. First, the microscopic image was segmented into Ferrite, Martensite, and Bainite regions. The phase structure's geometric property was used to identify different phases present inside the micrograph. After phase detection, the volume fraction of each region is calculated.

Effect of ultra-fast heating on microstructure and mechanical properties of cold-rolled low-carbon low-alloy Q&P steels with different austenitizing temperature

We performed ultra-fast heating (150 °C/s) quenching and partitioning (Q&P) processes to a cold-rolled low-carbon low-alloy steel. Adjusting the annealing temperature, we obtained two types of ferrite-containing Q&P steels with different matrix structure, i.e., martensitic matrix and ferritic matrix. The effect of ultra-fast heating on microstructure evolution and mechanical properties was analyzed, compared with the samples treated with conventional heating rate (10 °C/s). We also investigated the strain partition and fracture behaviors, basing on in-situ tensile tests under SEM. Results show that ultra-fast heating can significantly increase the A c1 and A c3 temperatures, and extend the temperature span of intercritical zone. It can also delay the complete recrystallization of deformed ferrite and promote the austenite nucleation, which leads to the structure refinement of the sample with martensitic matrix, improving both the strength and ductility. The increase of austenite nucleation rate and the incomplete recrystallization of deformed ferrite jointly promote the austenite transformation, which results in a distinct increase of martensite islands fraction in the sample with ferritic matrix, leading to its obvious increase of tensile strength and decrease of ductility. Strain partition is an important factor affecting the TRIP effect in ferrite-containing Q&P steels. For the sample with a martensitic matrix, retained austenite mainly possesses a film-like morphology and exists between martensite laths. The relatively high mechanical stability of retained austenite films and low local strain in martensitic regions result in the weak TRIP effect. The retained austenite in the sample with a ferritic matrix mainly distributes among ferrite grains and exhibits a blocky morphology. The relatively low mechanical stability of blocky retained austenite and high local strain in ferrite jointly enhance the TRIP effect. • Ultra-fast heating delays ferrite recrystallization. • Ultra-fast heating restrains martensite tempering. • Ultra-fast heating results in grain refinement of martensitic matrix. • Strain partition is a crucial factor controlling TRIP effect. • Main ductility origin is compatible deformation of matrix structures.

Large elastocaloric effect in as-cast Ni-Mn-Sn-Fe ferromagnetic shape memory alloys

The Ni-Mn-Sn ferromagnetic shape memory alloys exhibit excellent both magnetic field-induced magnetocaloric effect and uniaxial stress-induced elastocaloric effect. However, the intrinsic brittleness and narrow refrigeration temperature regions hinder their practical applications in elastocaloric and magnetocaloric as well other fields. In this work, the as-cast Ni44-xFexMn46Sn10 (x = 1, 2, 3) alloys are prepared directly by cooling solidification. The as-cast alloys improve the mechanical properties and broaden the martensitic transformation temperature region due to the presence of dendrites. The dendrites prevent cracking formation and propagation along the grain boundaries, and the addition of Fe-atoms enriched in the interdendritic region further optimizes the mechanical performance. In addition, the as-cast Ni41Fe3Mn46Sn10 alloy exhibits a large adiabatic temperature variation up to −10.3 K at a moderate stress of 350 MPa. Accordingly, direct cooling solidification of as-cast alloys could be a novel and feasible method for studying elastocaloric cooling technology.

Characterization of the cladding layer by laser cladding of 9Cr18Mo powder on 3Cr14 martensitic stainless steel and the impact of martensite obtained through post heat treatment on hardness

In this study, the relationship between microstructure and hardness of the cladding layer obtained from a real laser cladding knife was investigated. It was developed for high-end knives by laser cladding of 9Cr18Mo powder on the cutting edge of 3Cr14 martensitic stainless steel. The study indicated that martensite-free matrix structure (austenite with small amount of network Cr7C3) formed after cladding was responsible for the low hardness (420 HV) of the cladding layer. To enhance the hardness, post heat treatment (PHT) and cryogenic treatment (CT) were used. The results suggested that PHT had a significant effect on hardness enhancement, and the subsequent CT could further improve the hardness. The hardness was increased to ~700 (PHT) and 760 (PHT+CT) HV respectively, which was higher than that of 3Cr14 matrix (~620 HV). The mechanism is that PHT promotes the precipitation of Cr23C6 and then reduces the Ni and Mo equivalent (Nieq and Creq) of cladding layer matrix to austenite and martensite (A+M) region, thus promoting the formation of martensite and increasing the hardness. The subsequent CT further induces martensitic transformation of retained austenite (RA) and reduces the content and size of RA, and thus further increases the hardness.

Study of the microstructure and mechanical property relationships of gas metal arc welded dissimilar Hardox 450 and S355J2C+N steel joints

This research reports the investigation of the dissimilar welding of Hardox 450 and S355J2C+N steels, which have two different superior properties, by the gas metal arc welding (GMAW) method in terms of microstructure and mechanical properties. Experiments were performed using mechanical tests such as Vickers microhardness (HV 0.1), bending, Charpy V-Notch impact, wear, and tensile test. Optical microscopy (OM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analyzes have been implemented. A variation in the welded joint microstructure was observed, which affect the mechanical properties. Grain size distribution in area fraction was determined from the EBSD maps of S355J2C+N steel, welded zone, heat affected zone (HAZ) and Hardox 450 steel. The hardness value was measured 311 ± 8 HV for Hardox 450 base material. While the hardness of the S355J2C+N base metal was ∼187 ± 8 HV, the hardness of the weld center was measured as 249 ± 8 HV. Mechanical strength analysis revealed that the yield strengths of base metals were 513 ± 8 MPa and 1464 ± 8 MPa for S355J2C+N and Hardox 450, respectively. The highest tensile strength of the sample extracted from the longitudinal direction of the welded joint is 899 ± 8 MPa. The highest tensile strength of the transverse sample, which was subjected to the tensile tests, was determined as 699 ± 7 MPa and it fractured from the S355J2C+N steel which has less strength. The joint efficiency was determined as ∼133%. The weld zone has sufficient toughness and the change in toughness values in the HAZ is small. The grain size increased from martensitic Hardox 450 steel region to S355J2C+N region, in addition to this, the hardness decreased with the effect of transition from martensitic structure region to ferritic structure region. The welding zone is compatible with two different materials and has a high plastic deformation capability. With the welding procedure followed in the study, Hardox 450 and S355J2C+N dissimilar materials were successfully combined, and it was determined that this welded joint was scientifically and industrially applicable.