Vahid Javaheri

University of Oulu · Department of Material Engineering and Process Technology

Austenitic heat-resistant steels are particularly suitable for applications where service conditions comprise high temperature. The demand for better performance has motivated developments in these steels. In this work, Ti and Nb were added to austenitic heat-resistant steels, Fe-12Ni-25Cr-0.4C, wt.% simultaneously. Microstructural changes were stu...

A field emission scanning electron microscope equipped with EBSD has been employed to evaluate the role of 0.013 wt% Nb on the evolution of the microstructure and texture of a novel thermomechanically processed low-alloy, medium-carbon steel. Specimens were subjected to hot-rolling with a total reduction of 80%, four passes in the recrystallization...

The design of a new steel with specific properties is always challenging owing to the complex interactions of many variables. In this work, this challenge is dealt with by combining metallurgical principles with computational thermodynamics and kinetics to design a novel steel composition suitable for thermomechanical processing and induction heat...

Field emission scanning electron microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) have been employed to investigate the effect of niobium and phase transformation temperature on the evolution of microstructure and texture in a novel thermomechanically processed, medium‑carbon, low-alloy steel intended for slurry pipel...

Slurry erosion is a severe problem and a major concern for slurry handling equipment, as it leads to considerable expense caused by failures, downtime and material replacement costs. Slurry erosion is dependent on several parameters such as slurry properties, service conditions, and material properties. Hence, much high-quality research has been ai...

Rapid cyclic hardening cycles were carried out on a thermomechanically processed, medium-carbon, low-alloy steel to refine the microstructure by decreasing the prior austenite grain structure. The main aim was to explore the role of cyclic treatment on microstructure refinement and subsequently on the mechanical properties. For this purpose, a Glee...

Numerous industrial applications, particularly those in the transport industry, require the joining of dissimilar materials which offers considerable benefits in terms of low cost, design flexibility, and weight reduction for overall structures. The problems associated with conventional fusion welding processes have stimulated researchers in recent...

Ultra-high strength steels are widely utilized in many applications operating in harsh abrasive wear conditions. For instance, the machineries used in mining and mineral handling or in agricultural sector require robust, but cost-effective wear-resistant materials. Steels provide excellent combination of mechanical properties and usability. This st...

A combination of physical simulation and laboratory rolling experiments, including thermomechanical rolling and low-temperature ausforming, was conducted for designing a suitable processing route to enable phase transformation from austenite to ultrafine bainite in a medium-carbon steel. Following low-temperature ausforming at 500-550 °C, two diffe...

Third generation advanced high-strength steels, e.g., quenched and partitioned steels, are forthcoming structural materials, which consist of a martensitic matrix and a substantial proportion of stabilized residual austenite for improved deformability. A novel less energy-intensive processing route of direct-quenching and partitioning advances this...

New ultrahigh-strength steels have been developed to meet the need for better performance, load bearing capacity , safety and weight saving. However, the design guidelines are incomplete, especially regarding the design of welded ultrahigh-strength steel components in fluctuating operating conditions. This reduces usability and can cause serious sa...

A novel processing route is proposed to create a heterogeneous, multiphase structure in a medium Mn steel by incorporating partial quenching above the ambient, warm deformation, and partial recrystallization at high partitioning temperatures. The processing schedule was implemented in a Gleeble thermomechanical simulator and microstructures were ex...

The extremely altered topmost surface layer, known as the white layer, formed in a medium-carbon low-alloy steel as result of impacts by angular 10–12 mm granite particles during the slurry erosion process is comprehensively investigated. For this purpose, the characteristics, morphology, and formation mechanism of this white layer are described ba...

The Performance through Materials Research Webinar was organized by the PerforMat network funded by Academy of Finland. The focus was on the latest advances in the materials research. Especially the need for the improved performance and resource efficiency of advanced materials to overcome industrial challenges is highlighted. https://projects.tuni...

This study investigates the fatigue performance of additively manufactured steel CX under uniaxial high cycle loading. The results show that surface quality was the most influential parameter that changed the fatigue behavior of the material, compared to combinations of building orientation and heat treatment as other fabrication parameters. Conseq...

Hot compression tests were performed on Mn–25Ni–5Cr at temperatures of 850–1000 °C and strain rates of 0.001–1 s⁻¹. The flow curves at low strain rates were typical of dynamic recovery. However, at high strain rates, the flow curves were characterized by work hardening and slight flow softening proposing dynamic recrystallization. SEM-EDS observati...

The data available in this article presents the microstructural information achieved via scanning electron microscopy and electron backscatter diffraction to evaluate the microstructure of maraging stainless steel 13Cr10Ni1.7Mo2Al0.4Mn0.4Si, in its as-built and heat-treated conditions, fabricated by laser powder bed fusion. In addition, the statist...

The novel processing concept of direct quenching and partitioning (DQ&P) has been explored with a medium-carbon (0.4 wt.% C) steel to evaluate and optimize the processing route for excellent property combinations. New compositional design approach was based on physical simulation studies aiming to understand the influence of varying silicon content...

This study investigates the effects of build orientations, heat treatment, and mechanical machining (as processing and post-processing factors) on the microstructure, quasi-static mechanical properties, strain hardening, notch toughness, and residual stress of additive manufactured 13Cr10Ni1.7Mo2Al0.4Mn0.4Si maraging stainless steel, known commerci...

Ultra-high strength steels (UHSS) have a determining role in construction and industry. Furthermore, welding as the primary joining process for steel has a similar role in promoting its applications. Therefore, welded UHSS have a vital role in related applications. However, due to their complex microstructures, these steels are more prone to harmfu...

The presence of acicular ferrite (AF) in the heat-affected zone (HAZ) of steels used offshore is generally seen as beneficial for toughness. In this study, the effects of varying fractions of AF (0-49 vol.%) were assessed in the simulated, unaltered and coarse-grained heat-affected zones (CGHAZ) of three experimental steels. Two steels were deoxidi...

Various contributors have been suggested so far to explain the variation of mechanical properties of Fe-Co-V magnetic alloys, but a comprehensive understanding is still lacking. In the present study, the variation of hardness, tensile yield strength (YS), and elongation at room temperature were determined for an 86% cold-rolled Fe-50Co-10V (wt.%) a...

A combination of experimental and numerical approaches was applied for constructing a dynamic model for thermomechanical processing, which was used for simulating laboratory rolling and cooling, and for designing a cooling path to enable phase transformation from austenite to ultrafine (∼50–100 nm) bainitic laths. Physical thermomechanical simulati...

The influence of boron as well as boron with niobium additions on the phase transformation behaviour, resultant microstructures, and mechanical properties of thermomechanically controlled hot-rolled and direct-quenched low-carbon bainitic steel plates was investigated. Also, the probable factors that could inhibit their specific merits on hardenabi...

This work aims to study the effect of cold forming on the texture evolution during the manufacturing of rectangular hollow sections. Conventional TMCP steel and a direct-quenched steel in 420 MPa strength level are compared. The texture was characterized at the centerline (S=0) and both surfaces (S=0.8) for base material, four flat side and one cor...

Thermomechanical processing consisted of hot-rolling in the austenitic region with deformation both above and below the non-recrystallization temperature. Immediately after rolling, specimens were directly quenched in water to three different temperatures of 560 °C, 420 °C and room temperature. The first two samples, which were quenched to 560° C a...

The surface structure and properties of a cast piston alloy were improved after friction stir processing at a tool rotation rate of 710 rpm and tool traverse speed of 100 mm/min. The microstructure of the base and processed materials were characterized using an optical microscope, and a scanning electron microscopy equipped with energy dispersive s...

This work will be presented in the 19th International Conference on Textures of Materials (ICOTOM 19) which be held virtually on March 1 to 4, 2021. More info about the conference can be found here: http://icotom19.com

Grain refinement has been widely used to enhance the hardness and toughness properties of metallic materials. However, the effect of prior austenite grain refinement on the final martensitic microstructure and wear performance of steels is not yet fully understood. In this study, induction hardening treatment with heating rates in the range 50 - 50...

Bending behavior of a new thermomechanically processed low-alloy steel containing 0.40 wt.% carbon has been investigated. The processing included laboratory hot rolling to 10 mm thick strips followed by direct quenching to different quench-stop temperatures followed by slow furnace cooling to room temperature stimulating hot strip mill processing....

The effect of austenite deformation on carbon partitioning and transformation to athermal and isothermal martensite, and bainite during quenching and partitioning (QP) is described for three steel compositions: Fe-0.3C-0.6Si-1.1Al, Fe-0.3C-1.0Si and Fe-0.3C-0.5Si-0.5Al. Microstructures were characterized using SEM-EBSD, TEM and XRD. Austenite decom...

This paper presents an investigation into the mechanical properties of ultra-high strength steels (UHSSs) (with nominal yield stress of 960 and 1100 MPa) after welding. Seven weld thermal cycles were simulated using a Gleeble 3800 thermal-mechanical machine. These cycles represented the temperature-time history of the joint at various distances fro...

The effect of strain rate on flow behaviors of three beta Ti alloys with different beta phase stability was studied. The alloys were subjected to compression deformation at four strain rates ranging from 7×10-5 to 7×10-2 s-1 at room temperature. Microstructure evolution was characterized using laser scanning microscopy and electron backscattered di...

Typically, in processing of Fe-Co-V type magnetic alloys, hot rolled sheets are being severely cold rolled and then annealed at a specific temperature for an appropriate soaking time. In this work, in order to achieve the optimal magnetic properties, effect of various annealing cycles after 86% cold rolling on a 40Fe-50Co-10V (wt.%) alloy were exam...

Deterioration of the toughness in heat-affected zones (HAZs) due to the thermal cycles caused by welding is a known problem in offshore steels. Acicular ferrite (AF) in the HAZ is generally considered beneficial regarding the toughness. Three experimental steels were studied in order to find optimal conditions for the AF formation in the coarse-gra...

The bending properties of a new thermomechanically processed medium-carbon (0.40 wt% C) low-alloy steel, intended for the slurry transportation pipeline application, have been investigated. The studied material was hot-rolled to 10 mm thick strips followed by direct quenching to two different quench-stop temperatures (QST) of 560 °C and 420 °C. The...

Despite of extensive investigations conducted on magnetic Fe-Co-V alloys, some aspects of microstructural evolution during annealing of cold rolled sheets have not yet been clarified yet. Various techniques such as dilatometry, X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM, SEM) as well as ThermoCalc predictions were e...

The grain growth kinetics of two beta titanium alloys, Ti–4733 and Ti–5553 was studied over a temperature range of 850 °C–1000 °C. The more stable alloy i.e. Ti–4733, showed a smaller average grain size and slower growth rate compared to Ti–5553 at a same annealing condition. The results showed that the uniformity of grain size decreased initially...

The sensitization of austenitic stainless steels is dependent on various factors such as chemical composition, heat treatment temperature and time. To study these effects, the degree of sensitization in five austenitic stainless steel compositions that were subjected to isothermal heat treatments in the temperature range 550 - 820 °C has been deter...

Prior austenite grain size has a marked effect on the hardenability, strength, and impact toughness properties of steels. This study was conducted in order to understand the effect of prior austenite grain size and morphology on the mechanical properties and abrasive wear performance of an ultra-high strength steel. A commercial quenched 500 HB gra...

The kinetics of strain-induced martensite (SIM) formation in a Ti-bearing 201L stainless steel were evaluated and compared to the existing results of two conventional stainless steel grades; i.e., 201L and 304L AISI. The effects of strain rate and rolling pass reduction on the kinetics of SIM formation during cold rolling were investigated. The Ti-...

Abstract Purpose: The purpose of this work is to determine the induction hardening behavior of a new steel composition. For this purpose, Flux2D commercial software together with a Gleeble thermomechanical simulator has been used to numerically and physically simulate the material properties profile of an induction hardened slurry transportation...

The effect of grain size in the range 72 to 190 μm and carbon content in the range 0.105–0.073 wt.% on the intergranular corrosion of the austenitic stainless steel 301 has been investigated. Grain boundary chromium depletion has been studied directly using energy dispersive X-ray spectroscopy combined with scanning transmission electron microscopy...

This thesis has been made within the European Industrial Doctorate (EID) project called Mathematics and Materials Science for Steel Production and Manufacturing, abbreviated as MIMESIS, which has five partners: EFD Induction in Norway; SSAB, Outokumpu, and the University of Oulu in Finland; and Weierstrass Institute for Applied Analysis and Stochas...

Even after extensive research for decades on cold-rolled magnetic Fe-Co-V alloys, many aspects of ferrite recrystallization are still unclear. In order to analyze the progress of recrystallization in an Fe-50Co-10V (in wt.%) alloy, different thermal cycles were conducted for an 86% cold-rolled thin sheet (~140 μm). A comprehensive phase characteriz...

Computer simulations of steel microstructural development provide a powerful tool, which can form the basis of mechanical property predictions. However, in order to create detailed understanding of the factors affecting the properties, the model should predict microstructural evolution during cooling. The present study compares the results of cellu...

Numerical and Gleeble experimental data are combined to predict potential microstructure and hardness profiles through the wall thickness of an induction hardened slurry transportation pipe made of a recently developed 0.4 wt% C, Nb-microalloyed steel. The calculated thermal history of various positions through the wall thickness of an industrial p...

Flux2D commercial software together with a Gleeble thermomechanical simulator has been employed to numerically and physically simulate the material properties profile of an induction hardened slurry transportation pipe made of a recently developed 0.4 wt.% C, Nb-microalloyed steel. After calculating the thermal history of a 400 mm diameter, 10 mm t...

The induction hardening behavior of a new, hot-rolled 0.4 wt% carbon steel with the two different starting microstructures of upper and lower bainite has been simulated using a Gleeble 3800. The effect of heating rate in the range 1–500 °C/s on austenite grain size distribution has been rationalized. Dilatometry together with Scanning Electron Micr...

Corrigendum

The induction hardening behavior of a new, hot-rolled 0.4 wt.% carbon steel with the two different starting microstructures of upper and lower bainite has been simulated using a Gleeble 3800. The effect of heating rate in the range 1 - 500 {\deg}C/s on austenite grain size distribution has been rationalized. Dilatometry together with Scanning Elect...

This work explores the effect of heating rate on the prior austenite grain size and hardness of a thermomechanically processed novel niobium-microalloyed 0.40 % carbon low-alloyed steel intended for use in induction hardened slurry pipelines. The aim was to identify the heating rates that lead to the maximum hardness, for high wear resistance, and...

p>Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used in high temperature structural applications. Their composition include Nb as strong carbide former. Electron Backscatter Diffraction (EBSD) investigations revealed that, in the as-cast condition, alloys exhibit austenitic matrix with intergranular primary carbides such as MC, M<sub>23</su...

The study is conducted to determine the effect of quenching and tempering processes on microstructural evolutions and abrasive properties of medium carbon-high chromium steel. For this purpose, Austenitizing was performed at the temperatures of 1000 °C for 15 min followed by oil quenching. To determine the optimum tempering temperature, tempering t...

The effect of centerline and subsurface microstructures on the crystallographic texture of three 8 mm thick low-alloyed hot-rolled and direct-quenched ultrahigh-strength strip steels with yield strengths in the range 800 – 1100 MPa has been investigated. Detailed microstructural features were studied using LCSM, FESEM, FESEM-EBSD. In addition textu...

A satisfying video of super-fast induction (through) hardening of a carbon steel producing very fine grain structure. The sample has been intended to be tested in a high-speed slurry pot test rig to evaluate its slurry erosion behavior. Further information about this work can be found from link below: https://www.sciencedirect.com/science/article/...

The ultimate objective with this project is to determine a suitable chemical composition together with high-frequency induction welding and induction heat treatment parameters that will enable the economic production of a tough monolithic pipe with extremely good wear resistance on the inner surface, i.e. a low-alloy medium-carbon steel. The main a...

In the present study, the constitutive flow behavior of a 2205 cast duplex stainless steel has been evaluated during warm compression testing in the temperature range 900-1100 ◦C at strain rates in the range 0.001-0.1 s-1, aided with the micro structural characterization of deformed specimens. Moreover, the constitutive analysis of flow stress was...