Effect of Different Austempering Heat Treatments on Corrosion Properties of High Silicon Steel

A novel high silicon austempered (AHS) steel has been studied in this work. The effect of different austenitizing temperatures, in full austenitic and biphasic regime, on the final microstructure was investigated. Specimens were austenitized at 780 °C, 830 °C, 850 °C and 900 °C for 30 min and held isothermally at 350 °C for 30 min. A second heat treatment route was performed which consisted of austenitizing at 900 °C for 30 min and austempering at 300 °C, 350 °C and 400 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used to evaluate the microstructural evolution. These techniques revealed that the microstructures were composed of carbide-free bainite, ferrite, martensite and retained austenite (RA) in different volume fractions (Vγ). An aqueous borate buffer solution with 0.3 M H3BO3 and 0.075 M Na2B4O7∂10H2O (pH = 8.4) was used for corrosion tests in order to evaluate the influence of the different volume fractions of retained austenite on the corrosion properties of the specimens. The results showed that when increasing the austenitization temperatures, the volume fractions of retained austenite reached a maximum value at 850 °C, and decrease at higher temperatures. The corrosion properties were investigated after 30 min and 24 h immersion by means of potentiodynamic polarization (after 30 min) and electrochemical impedance spectroscopy (after both 30 min and 24 h) tests. The corrosion resistance of the samples increased with increases in the volume fraction of retained austenite due to lower amounts of residual stresses.

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Estimating Volume Fractions of Microstructural Constituents in Austempered High Silicon Alloyed GJS 600-10 Ductile Iron through Magnetic Measurements (VSM)

Materials Science Forum ◽

10.4028/www.scientific.net/msf.907.50 ◽

2017 ◽

Vol 907 ◽

pp. 50-55

Author(s):

Yakup Yürektürk ◽

Murat Baydogan

Keyword(s):

Heat Treatment ◽

Ductile Iron ◽

Retained Austenite ◽

Volume Fraction ◽

Magnetic Measurements ◽

Ferritic Matrix ◽

Volume Fractions ◽

High Silicon ◽

New Generation

In this paper, austempering heat treatment was applied to a new generation high silicon GJS 600-10 grade ductile iron with an initial ferritic matrix. Different austempering temperatures of 270, 330 and 390°C were applied after austenitizing at 975°C for 120 min. Depending on the austempering temperatures, lower and upper ausferritic microstructures were obtained. Results showed that volume fraction of the retained austenite in the ausferritic microstructures, which was estimated by VSM technique is well correlated with those estimated by XRD technique.

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Influence of the Processing Variables on the Microstructure Evolution of a Bainitic Carbide-Free Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.867 ◽

2016 ◽

Vol 879 ◽

pp. 867-872 ◽

Cited By ~ 1

Author(s):

M.C. Taboada ◽

I. Gutiérrez ◽

D. Jorge-Badiola ◽

S.M.C. van Bohemen ◽

F. Hisker ◽

...

Keyword(s):

Retained Austenite ◽

High Strength Steels ◽

High Strength ◽

High Volume ◽

X Ray Diffraction ◽

Tempered Martensite ◽

Trip Steels ◽

Volume Fractions ◽

Advanced High Strength Steels ◽

Processing Variables

New trends focused on achieving higher performance steels has led to a so-called 3rd Generation Advanced High Strength Steels (AHSS), in which the typical polygonal ferrite found in TRIP steels as a matrix phase is replaced by harder phases as Carbide-Free Bainite (CFB) and/or (tempered) martensite. Besides, large volume fractions of retained austenite (R.A.) with adequate stability are aimed for to improve the formability of the steels. Si containing steels are regarded as the most suitable to retard cementite formation and consequently reach high volume fractions of RA. In this work, CFB annealing schedules were applied to dilatometer samples of Fe-0.22C-2.0Mn-1.3Si. The overaging temperature TB was varied between 390 oC and 480 oC, and other processing variables investigated were the austenitizing temperature Taus, and the overaging holding time tB. The annealed samples analyzed with LOM, FEG-SEM, EBSD and X-ray diffraction techniques show that markedly different complex microstructures made up of bainite, ferrite, MA phase and retained austenite (R.A) are accomplished depending on the specific thermal cycle. These results are described in detail and discussed in relation to the dilatometry measurements.

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An Investigation on Anti-Corrosion Properties of Electroplated Copper-Graphene Nano-Composite Films

Materials Science Forum ◽

10.4028/www.scientific.net/msf.978.499 ◽

2020 ◽

Vol 978 ◽

pp. 499-504 ◽

Cited By ~ 1

Author(s):

Akhya Kumar Behera ◽

Archana Mallik

Keyword(s):

Thin Films ◽

Corrosion Rate ◽

Pure Copper ◽

Copper Matrix ◽

Reinforcement Particle ◽

Graphene Sheets ◽

Borate Buffer Solution ◽

Buffer Solution ◽

Corrosion Properties ◽

Electroplated Copper

In this report, graphene sheets used as reinforcements for improvement of anti-corrosion properties have been synthesized by electrochemical intercalation and exfoliation process. The (001) and (002) plane of graphene sheets at a 2θ angle of 13.2 and 26.13 confirmed by X-ray diffraction pattern. High-resolution TEM confirms 8-12 layers of graphene present in the final products. The as-received graphene sheets have been used as reinforcement with copper matrix to synthesize Cu-Gr nanocomposite by electrodeposition method. The results and investigations of Cu-Gr composite thin films deposited from the bath containing 0.1g/L and 0.5g/L graphene concentrations with acidic copper sulfate solution have been compared. The surface morphology and roughness of composites were studied by SEM, AFM and surface profiler. The presence of graphene in Cu-Gr nanocomposite confirmed by EDS analysis. It was observed that the reinforcement particle has increased the mechanical properties of Cu-Gr composite (by 30%) with the addition to the copper matrix. The corrosion resistance of sample was studied by Tafel extrapolation method in standard borate buffer solution. For nanocomposites of 0.5g/L graphene, the values of Tafel constants are, βa=177.37 mv, βc=138.51 mv, Icorr = 9.3165×10-7Amp/cm2, Ecorr = -0.051 volts and corrosion rate 0.01028 mm/a as comparison to the corrosion rate of pure electroplated copper of a value of 0.029 mm/a. The corrosion rate of 0.5g/L Cu-Gr composite was found to be decreased by 2.7 times as compared to pure copper thin films. The structure of the films before and after corrosion was also analyzed to co-relate the electrochemical and structural relationship.

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Investigation of time-dependent corrosion behavior of Sr-modified AlSi12 alloy

International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) ◽

10.1515/ijmr-2020-1110410 ◽

2020 ◽

Vol 111 (4) ◽

pp. 339-346

Author(s):

Gökçe Hapçı Aǧaoǧlu ◽

İnal Kaan Duygun ◽

Gökhan Orhan

Keyword(s):

Particle Size ◽

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Corrosion Behavior ◽

Immersion Time ◽

Volume Fraction ◽

Electrochemical Impedance ◽

Eutectic Structure ◽

Time Dependent ◽

Corrosion Properties

Abstract The effect of Sr addition on the microstructure and time-dependent corrosion properties of the AlSi12 eutectic alloy was investigated. The modified alloy contained 90 ± 3 ppm Sr. The microstructural differences in the eutectic structure of AlSi12 alloys were assessed in terms of the Si particle size and a-Al volume fraction. The unmodified and Sr-modified alloys were immersed for 1, 24, 72 and 120 h in 3.5 wt.% NaCl. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were performed to analyze the corrosion characteristics of the alloys. Sr addition led to a decrease in the Si particle size, and the formation of long dendritic a-Al. It was found that the presence of Sr resulted in more stable corrosion behavior up to 24 h. The deterioration of the corrosion behavior of Sr-modified alloy was observed with the further increase of immersion time.

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Processing, Microstructure and Properties of Laminated Ni-Intermetallic Composites Synthesised Using Ni Sheets and Al Foils

Archives of Metallurgy and Materials ◽

10.2478/v10172-011-0076-y ◽

2011 ◽

Vol 56 (3) ◽

pp. 693-702 ◽

Cited By ~ 13

Author(s):

M. Konieczny ◽

R. Mola ◽

P. Thomas ◽

M. Kopciał

Keyword(s):

Microprobe Analysis ◽

Volume Fraction ◽

Laminated Composites ◽

Intermetallic Phase ◽

Intermetallic Phases ◽

Solid State Reactions ◽

X Ray Diffraction ◽

X Ray ◽

Microstructure And Properties ◽

Final Microstructure

Processing, Microstructure and Properties of Laminated Ni-Intermetallic Composites Synthesised Using Ni Sheets and Al FoilsThe laminated Ni-(NiAl3+Ni2Al3) and Ni-Ni2Al3intermetallic composites were fabricated by reaction synthesis in vacuum using Ni sheets and Al foils. The aluminium layers were completely consumed due to the formation of intermetallic phases. The Ni-Al reaction at 620°C was studied by interrupting in steps the reaction process to observe the microstructural changes. The final microstructure consisted of alternating layers of intermetallic phases and unreacted nickel can be designed easily because the stable structures of the composites depend only on the treating time. Microstructural examinations using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray microprobe analysis (EDX) demonstrated that after 1h of treatment Ni2Al3is the predominant intermetallic phase. The formation of the Ni2Al3phase is thermodynamically favoured over the formation of the other phases and can be understood from the steps occurred through a series of solid state reactions. The tensile strength of the laminated composites increases with an increase of the volume fraction of the intermetallic products. However, it decreases after long heat treatment because the Ni2Al3/Ni2Al3interfaces can very easily delaminate due to a very weak bonding caused by continuous Al2O3inclusions. Observations show that the laminated composites exhibit a mixture of brittle fracture of intermetallics and ductile one of residual Ni layers.

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Comments on determining X-ray diffraction-based volume fractions of retained austenite in steels

Powder Diffraction ◽

10.1154/1.1402627 ◽

2001 ◽

Vol 16 (4) ◽

pp. 198-204 ◽

Cited By ~ 2

Author(s):

C. K. Lowe-Ma ◽

W. T. Donlon ◽

W. E. Dowling

Keyword(s):

Retained Austenite ◽

Volume Fraction ◽

X Ray Diffraction ◽

Experimental Conditions ◽

X Ray ◽

Profile Fitting ◽

Diffraction Peaks ◽

Diffraction Patterns ◽

Heat Treatment Regimes ◽

Integrated Intensities

Retained austenite is an important characteristic of properly heat-treated steel components, particularly gears and shafts, that will be subjected to long-term use and wear. Normally, either X-ray diffraction or optical microscopy techniques are used to determine the volume percent of retained austenite present in steel components subjected to specific heat-treatment regimes. As described in the literature, a number of phenomenological, experimental, and calculation factors can influence the volume fraction of retained austenite determined from X-ray diffraction measurements. However, recent disagreement between metallurgical properties, microscopy, and service laboratory values for retained austenite led to a re-evaluation of possible reasons for the apparent discrepancies. Broad, distorted X-ray peaks from un-tempered martensite were found to yield unreliable integrated intensities whereas diffraction peaks from tempered samples were more amenable to profile fitting with standard shape functions, yielding reliable integrated intensities. Retained austenite values calculated from reliable integrated intensities were found to be consistent with values obtained by Rietveld refinement of the diffraction patterns. The experimental conditions used by service laboratories combined with a poor choice of diffraction peaks were found to be sources of retained austenite values containing significant bias.

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High Versatility of Niobium Alloyed AHSS

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0230 ◽

2017 ◽

Vol 62 (3) ◽

pp. 1485-1491 ◽

Cited By ~ 11

Author(s):

L. Kučerová ◽

K. Opatová ◽

J. Káňa ◽

H. Jirková

Keyword(s):

Heat Treatment ◽

Retained Austenite ◽

Volume Fraction ◽

High Strength ◽

Processing Parameters ◽

High Ductility ◽

Processing Strategies ◽

Cooling Schedules ◽

Final Microstructure ◽

Steel Processing

AbstractThe effect of processing parameters on the final microstructure and properties of advanced high strength CMnSiNb steel was investigated. Several processing strategies with various numbers of deformation steps and various cooling schedules were carried out, namely heat treatment without deformation, conventional quenching and TRIP steel processing with bainitic hold or continuous cooling. Obtained multiphase microstructures consisted of the mixture of ferrite, bainite, retained austenite and M-A constituent. They possessed ultimate tensile strength in the range of 780-970 MPa with high ductility A5mmabove 30%. Volume fraction of retained austenite was for all the samples around 13%. The only exception was reference quenched sample with the highest strength 1186 MPa, lowest ductility A5mm= 20% and only 4% of retained austenite.

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Non-Destructive Quantitative Phase and Residual Stress Analysis Versus Depth Using Grazing X-Ray Diffraction

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.130.47 ◽

2007 ◽

Vol 130 ◽

pp. 47-52 ◽

Cited By ~ 1

Author(s):

S.J. Skrzypek ◽

M. Goły ◽

Wiktoria Ratuszek ◽

Mieczyslaw Kowalski

Keyword(s):

Residual Stresses ◽

Phase Analysis ◽

Retained Austenite ◽

Volume Fraction ◽

Ball Bearings ◽

X Ray Diffraction ◽

X Ray ◽

Quantitative Phase ◽

Diffraction Geometry ◽

Non Destructive

The non-destructive structure characterisation of surface layers for various kinds of ball bearings can be a powerful method in surface characterization and in quality control. The ball bearings were made of 100Cr6 steel and they were superfinished and mechanically burnished. An application of classical X-ray diffraction sin2ψ method and classical Bragg-Brentano diffraction geometry in these kinds of surface examinations make some problems in term of X-ray real depth of penetration. An application of methods based on grazing angle X-ray diffraction geometry, made possible to get real value of residual macro-stresses, retained austenite and additionally could be suitable in estimation of their gradient-like distribution versus depth under surface. An application of this geometry to X-ray diffraction phase analysis enabled to get phase contents versus thickness under surface in non-destructive way as well. The results are not infected by gradient-like distribution. The X-ray quantitative phase analysis was used to establish volume fraction of transformed retained austenite. Theoretical calculation of residual macro-stresses due to volume fraction of transformed austenite in ball bearings and following measurements of residual stresses were curried out as well. The mechanical burnishing of ball bearings caused big compressive residual stresses about – 1000 MPa and phase transformation of austenite in thin surface layer. These factors can influence on properties of following exploitation and durability.

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The influence of Co2+ concentration on som the properties of the electrodeposited zinc–cobalt alloy coatings

Acta Metallurgica Slovaca ◽

10.12776/ams.v24i3.1072 ◽

2018 ◽

Vol 24 (3) ◽

pp. 241 ◽

Cited By ~ 1

Author(s):

Malika Diafi ◽

Tahraoui Louiza ◽

Kelthoum Digheche ◽

Farida Khamouli

Keyword(s):

Alloy Composition ◽

Electrochemical Impedance ◽

Co2 Concentration ◽

Micro Hardness ◽

X Ray Diffraction ◽

Cobalt Alloy ◽

Corrosion Properties ◽

X Ray ◽

Continuous Current ◽

Nyquist Plots

The effects the concentration of cobalt on zinc-cobalt alloys obtained from sulphate baths under continuous current deposition are described. The deposit morphology was analyzed using Scanning Electron Microscopy (SEM) and an X-Ray Diffraction (XRD) was used to determine the preferred crystallographic orientations of the deposits. Protection against corrosion properties studied in a solution of 3 % NaCl in the potentiodynamic polarization measurements (Tafel), electrochemical impedance spectroscopy (EIS) to the potential of corrosion free. The parameters that characterize the corrosion behavior can be determined from the plots and Nyquist plots. It has been observed that the Zn–Co alloy is characterized by enhanced the resistance of corrosion compared to the Zn alloys. and the addition of Co in the Zn-Co increases the micro-hardness, XRD and SEM results an identify any coatings Zn-Co alloy composition reveals that. zinc-rich( η- phase) , cubic Co5Zn21 .

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STUDY OF ZN-NI ALLOY COATINGSMODIFIED BY NANO-AL2O3 PARTICLES INCORPORATION

Acta Metallurgica Slovaca ◽

10.12776/ams.v22i3.706 ◽

2016 ◽

Vol 22 (3) ◽

pp. 171 ◽

Cited By ~ 1

Author(s):

Malika Diafi ◽

Said Benramache ◽

Elhachmi Guettaf Temam ◽

Adaika Mohamed Lakhdar ◽

Brahim Gasmi

Keyword(s):

Electrochemical Impedance ◽

Research Work ◽

Charge Transfer Resistance ◽

Diffraction Measurement ◽

X Ray Diffraction ◽

Corrosion Properties ◽

Transfer Resistance ◽

Characterization Methods ◽

Ni Alloy ◽

Steel Substrates

AbstractThe aim of this research work was to codeposit nano-Al2O3 particles into Zn-Ni alloy coatings in order to improve some surface ,properties, the influence of the concentration of Al2O3 is the principal object in order to improve the corrosion resistance of the deposit, which has been made by electroplating on steel substrates previously treated, have been studied by several characterization methods, as the X-ray diffraction, measurement of micro hardness and scanning electron microscopy (SEM), protection against corrosion properties studied in a solution of 3% NaCl in the potentiodynamic polarization measurements (Tafel), electrochemical impedance spectroscopy (EIS) to the potential of corrosion free. The parameters that characterize the corrosion behavior can be determined from the plots and Nyquist plots and chronopotentiometry. Trends of increasing the charge transfer resistance and the decrease of capacitance values. XRD and SEM results and identify any coatings Zn-Ni and Zn-Ni-Al2O3 alloy composition have similar phase ( γ-phase structure) and the addition of Al2O3 in the Zn-Ni matrix increases the microhardness, and we note the maximum hardness is obtained for 50 g/L Al2O3.

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