A. Najafizadeh

Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

[ 1 ] - The Effects of Nitrogen Addition on the Production of Ultrafine/Nano Grained AISI 201L Stainless Steel by Advanced Thermo-mechanical Process

In this study, the effects of nitrogen addition on the production of ultrafine/nano grained AISI 201L stainless steel by advanced thermo-mechanical process were investigated. Cast samples were first homogenized at 1200 °C for 4 h, hot-rolled at 1100 °C and finally, solution-annealed at 1150 °C for 2.5 h. Unidirectional and cross multipass cold rolling at 25 °C was carried out to 90% reduction i...

[ 2 ] - The Effect of Niobium on the Formation of Nanostructured Low Carbon Steel Using Martensite Treatment

The formation of nano/ultrafine grained ferrite in low carbon steels containing different amounts of niobium was investigated using thermomechanical treatment which consisted of annealing of 85% cold rolled martensite with different parameters. The specimens were characterized by optical and scanning electron microscopy and Vickers hardness test. A lamellar dislocation cell structure was formed...

[ 3 ] - The Effects of Martensite Thermomechanical Parameters on the Formation of Nano/Ultrafine Grained Structure in 201LN Stainless Steel

In this study, the effects cold rolling and annealing parameters during thermomechanical processing of the AISI 201LN stainless steel were investigated. The cast samples were homogenized, hot-rolled and solution-annealed to acquire a suitable microstructure for the subsequent thermomechanical treatment. Unidirectional and transverse multi-pass cold rolling at 25, 0 and -15 °C was carried out to...

[ 4 ] - Effect of annealing process on microstructure and mechanical properties of high manganese austenitic TWIP steel

In the present study, the influence of annealing temperature on mechanical properties and the microstructure of a high manganese austenitic steel (Fe-30Mn-4Al-4Si-0.5C) was investigated. X-ray diffractometry, optical and scanning electron microscopy, hardness and tensile tests were used to analyze the relationship between mechanical properties and microstructure after annealing process. The res...

[ 5 ] - Correcting the stress-strain curve in hot compression test using finite element analysis and Taguchi method

In the hot compression test friction has a detrimental influence on the flow stress through the process and therefore, correcting the deformation curve for real behavior is very important for both researchers and engineers. In this study, a series of compression tests were simulated using Abaqus software. In this study, it has been employed the Taguchi method to design experiments by the factor...

[ 6 ] - Influence of Aging Temperature on Mechanical Properties and Sound Velocity in Maraging Steel M350

In the present work, the influence of aging temperature on mechanical properties and sound velocity of Maraging steel M350 was investigated. For this purpose, first, samples were solution annealed at 825◦C for 2 hours and then age hardened at 510◦C-600◦C for 3 hours. Hardness, tensile and impact tests were used for determining mechanical properties and longitudinal ultrasonic velocity was used ...

[ 7 ] - Artificial neural network models for production of nano-grained structure in AISI 304L stainless steel by predicting thermo-mechanical parameters

An artificial neural network (ANN) model is developed for the analysis, simulation, and prediction of the austenite reversion in the thermo-mechanical treatment of 304L austenitic stainless steel. The results of the ANN model are in good agreement with the experimental data. The model is used to predict an appropriate annealing condition for austenite reversion through the martensite to austeni...

[ 8 ] - Color metallography; a suitable method for characterization of martensite and bainite in multiphase steels

Color metallography is a useful method for characterizing microstructures of steels with multiple phases. In this paper, application of three different color etching techniques for a bainitic-martensitic steel is reported. Comparisons between the results showed that 10% Na2S2O5 aqueous solution was the best etchant for distinguishing martensite, bainite and ferr...

[ 9 ] - Effects of Homogenization Conditions and Hot Rolling Parameters on Grain Refinement of an As-Cast 301 Stainless Steel

In this work, effects of homogenization time of 3 to 13 h at 1200 °C on the grain refinement of as-cast AISI 301 stainless steel after different hot rolling conditions were investigated. The results showed that the minimum grain size of 16±7 mm was achieved when homogenization took place at 1200 °C for 9 h followed by hot rolling at temperature range of 1000–1200 °C with strain of 0.8 and stra...

[ 10 ] - Dynamic Recrystallization by Necklace Mechanism During Hot Deformation of 316 Stainless Steel

The aim of this study is to investigate the nucleation of new grains by necklacing mechanism during dynamic recrystallization (DRX). The material used is 316 stainless steel. In order to modeling the deformation behavior during hot rolling, one-hit compression tests were performed at temperature range of 950-1100 °C with strain rates of 0.01-1s-1. The result shows that at the tempera...

[ 11 ] - The Strain Dependence of Post-Deformation Softening during the Hot Deformation of 304H Stainless Steel

Experiments were carried out in which the dependence of the fractional softening on temperature, time and strain rate was determined in a 304H stainless steel. Three prestrain ranges were identified pertaining to three different post-deformation softening behaviors: 1) prestraining to below the DRX critical strain: strongly strain dependent softening by SRX alone with softening kinetics control...

[ 12 ] - Structural and Mechanical Characterization of Austempered Cu - Sn Ductile Iron Alloys

The effect of heat treatment and alloying elements of copper and tin on the microstructure and mechanical properties of austempered ductile cast iron alloys is investigated. The austenitizing temperature of 890°C, the isothermal transformation (austempering) temperatures of 285, 335 and 375°C, and austempering times of 15, 30, 75 and 150 minutes are studied. The alloying elements of copper and ...

[ 13 ] - Effect of Composition on the Recrystallization Behavior of if Steels During Simulated Hot Strip Rolling

Flow curves are generated in muti-pass torsion tests for a titanium stabilized and a niobium stabilized IF steel. Two types of test schedule are used, one based on plate rolling and the other approximating strip rolling. The purpose of the former is to define the three critical temperatures of steel rolling. The strip schedules are varied in order to investigate the influence of increasing the ...

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