Hossein Monajati

• PhD
• Research Associate at École de Technologie Supérieure

Bake hardening (BH) is a vital part of special steel production. Studies in this field have focused on steels under homogeneous yielding, but until now, none have been conducted on the phenomena that occur for steels under heterogeneous yielding. In the current study, the effect of adding Nb and V alloying elements on the strength of ultra-low carb...

The severe deformation and temperature paths in the stir zone, also called weld nugget, of friction stir welded joints result, at very local levels, in significant microstructural variations, such as major differences in grain size or precipitation. One of the most common features of friction stir welds is the presence of successive material layers...

Linear friction welding (LFW) is a near net shape solid state joining technology for aerospace applications. In this study LFW of a recently introduced Ni-based superalloy, AD730™,with superior properties for use in the hot section of gas turbines was studied. In order to minimize the number of experiments for achieving sound welds, an analytical m...

Local mechanical properties of Ti-6Al-4V butt joints produced by friction stir welding (FSW) were investigated using the shear punch testing and correlated with the global mechanical properties, microstructure, and microtexture evolution of the joint. The conditions for obtaining defect-free joints, under high heat input conditions were determined...

In the present work, aluminum-3% brass composite sheets are produced by accumulative roll bonding (ARB) process up to nine passes at ambient temperature. Evolution of rolling texture is studied by texture measurement using X-ray diffraction method. The results show that ARB process leads to the formation of copper ({112} <111>) and Dillamore ({4 4...

The present work is conducted to study the microstructure and texture evolutions in an as-cast A206 aluminum alloy after applying severe plastic deformation. Toward this end, the material is severely deformed through accumulative back extrusion (ABE) technique at 200 °C and followed by assessing the room temperature mechanical properties of the pro...

Metallurgical and mechanical characterization of surface and subsurface regions in broached and shot-peened fir-trees in an industrial gas turbine disc made of Inconel-718 were carried out. High resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometry (EDS), electron backscatter diffraction (EBSD), X-ray diff...

A composite coating containing 10 wt-% of SiC and 90 wt-% CO-222 super alloy was coated with atmospheric plasma spray at two different currents on the surface of the 304 stainless steel. The aim of this research is to address the microstructure and phase formation during the plasma spray of Co-222/SiC composite coatings. The phase analysis, microst...

Multipass welding procedures are common methods for 13Cr4Ni steels' fabrication and repairs. Compared to a single-pass weld procedure, the weld microstructure in a multipass weld is more heterogeneous due to the complex local thermal cycles imposed by adjacent weld passes. Furthermore, the final microstructure and mechanical properties of these ste...

Cold spraying process was employed as a novel method to prepare electrocatalysts for hydrogen evolution by the water electrolysis process. Three electrode coatings were developed by cold spraying of nickel powder on aluminum substrates employing different coating parameters. The effect of the electrodes surface topography, microstructure, residual...

In this research, thermomechanical processing of a high-strength low-alloy steel was simulated through hot torsion testing. Average schedule and continuous cooling torsion after the actual schedule were used to determine the critical temperatures of the tested steel. Also, a simplified actual schedule with 79 % reduction in the austenite pancaking...

The magnetic properties of ferritic steels including the coercive field and the remanent induction are sensitive to microstructural features such as the grain size and the dislocation density. In this paper the effect of isothermal-annealing treatments at different temperatures on the coercive field and the remanent induction of industrially cold-r...

TWIP steels are a family of high-Mn austenitic steels having both high strength and high ductility used as automotive-body steels. In the present paper, the effect of an addition of Mo on the improvement of the mechanical properties of a TWIP steel (Fe-33Mn-3Si-2Al) is investigated. Different amounts of Mo were added to the chemical composition of...

The layering of a microstructure parallel to the direction of the material flow during the hot working process is called banding. In the present paper, the severity of ferrite-pearlite banding in the API-X42 microalloyed steel and its effects on the impact energy are studied. Specifically, the impact toughness is examined in the cases of banded and...

In this paper Al-CNT powder mixtures with 2 and 5% CNT weight percent were synthesized by mechanical alloying. Particle size distribution was measured by laser particle size analyzer. Effect of milling time and carbon nanotube content was characterized on particle size. X-ray diffraction analysis was conducted for different samples and powder cryst...

The hot deformation behavior of a Ni-Cu alloy was studied using hot compression testing in the temperature range of 950 °C–1150 °C and at strain rates of 0.001 s−1-1 s−1. Flow curves at low strain rates, up to 0.01 s−1, were typical of DRX characterized by a single peak, while at higher strain rates, the typical form of a DRX flow curve was not obs...

The flow behavior and microstructure evolution of AZ91 magnesium alloy during a thermomechanical process, hot compression test， was investigated. The specimens were hot compressed at a temperature ranging from 350 °C to 425 °C and at strain rate of 0.1 s −1 to the strains of 0.3, 0.5 and peak. Microstructural evolutions were studied using optical a...

TWIP steels are high Mn (17-35%) austenitic steels having strength and ductility concurrently. This makes them suitable for applications that need high strength and ductility like gas tanks and oil platforms. To these applications corrosion resistance of these steel is also of paramount importance and needs to be noticed. This was achieved by two u...

In this paper, a novel method for predicting mechanical properties of cold-rolled low carbon steel based on magnetic parameter measurement using Adaptive Neuro Fuzzy Inference System (ANFIS) is presented. The Yield Stress (YS) and Ultimate Tensile Strength (UTS) are predicted using two ANFIS models on the basis of B-H curve parameter measurement. B...

Cladding of steel with titanium alloys is used widely in aerospace, chemical and nuclear industries, to improve corrosion behavior and reduce production costs. Roll bonding is one of the solid state processes to produce this combination. In this research the high quality bonding of hot roll bonding of titanium on steel substrate was investigated in...

The effect of addition of Nb and Ti also cold rolling and annealing treatment on mechanical properties and microstructure of a twinning induced plasticity (TWIP) steel have been investigated. The results indicated that addition of Nb and Ti enhances strength. Also it is considered in the case that deformation twinning is suppressed, low stacking fa...

In this report, the feasibility of predicting mechanical properties using magnetic parameters measurements and artificial neural network (ANN) will be presented. The yield and ultimate tensile strength are predicted by means of two back-propagation neural networks on the basis of hysteresis loop parameter measurements and sample thickness. Inductiv...

In the present study, an artificial neural network (ANN) is used to describe the effects of processing parameters on the evolution of mechanical properties and formability of deep drawing quality (DDQ) steel sheets. This model is a feed forward back-propagation neural network (BPNN) with a set of 19 parameters including chemical composition, hot an...

In the present work, production of the chromium carbide was investigated by reduction of chromium oxide with methane-containing gas mixture. The experiments were conducted on the chromium oxide powder and methane gas at different temperatures, times, and gas mixtures. X-ray diffraction (XRD) analysis was used to characterize the products at differe...

Steel sheet metals are widely used in different industries due to their high strength, good weldability, availability, moderate cost, and the ability to form to complex 3D parts. The study of the formability of sheet metals is often done by means of Forming Limit Diagram (FLD) which presents the major and minor engineering strain thresholds under d...

The influence of various heat treatment conditions on the kinetics of dissolution, re-precipitation and growth in nickel base superalloy Udimet 720 (U720) was studied. Cubical shape samples were extracted from a forged blade and solution treated at 1110, 1140, 1150, 1160 and 1170 • C for holding times ranging from 2 to 24 h. Samples were quenched a...

The effect of processing parameters on the evolution of the microstructural characteristics of IMI834 were examined over the temperature range 950–1125 °C at constant strain rates of 0.001–1 s−1 and true strains up to 1.2. During isothermal deformation, differences in the flow softening behavior were observed for processing in the single-phase beta...

In this work, the flow stress behavior of near-α alloy IMI834 was investigated by compression testing under isothermal hot working conditions of varying temperature (between 950 °C and 1125 °C) and strain rates (between 0.001 s−1 and 1 s−1) up to a true strain of 0.8. The flow stress behavior revealed greater flow softening in the α–β region as com...

The influence of 5% prestain on γ′ precipitation during high temperature deformation of Udimet 720 was studied using stress relaxation. The occurrence of a stress plateau was associated with γ′ precipitation and verified by metallography examination. PTT diagram was determined for the alloy and related to the diffusion coefficient of γ′ forming ele...

The hot deformation behavior of nickel-base superalloy UDIMET 720 in solution-treated conditions, simulating the forging process of the alloy, was studied using hot compression experiments. Specimens were deformed in the temperature range of 1000 °C to 1175 °C with strain rates of 10−3 to 1 s−1 and total strain of 0.8. Below 1100 °C, all specimens...

Manufacturing of high-temperature titanium alloys for critical applications in aerospace, such as compressor parts of gas turbine engines, presents numerous challenges that are related to incorporating the complexity of the microstructural evolution into a restricted thermomechanical processing window. In particular, the series of primary and secon...

The influence of various heat treatment conditions on the kinetics of γ′ dissolution, re-precipitation and growth in nickel base superalloy Udimet 720 (U720) was studied. Cubical shape samples were extracted from a forged blade and solution treated at 1110, 1140, 1150, 1160 and 1170°C for holding times ranging from 2 to 24h. Samples were quenched a...

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