Modeling the Precipitation Kinetics of Cementite in Bainite in 0.17% Carbon Steel

2017 ◽  
Vol 898 ◽  
pp. 832-839 ◽  
Author(s):  
Yong Yang ◽  
Bin Wang ◽  
Zhao Dong Wang ◽  
Yan Mei Li ◽  
Guo Dong Wang ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Carbon Concentration ◽  
Unit Volume ◽  
Treatment Time ◽  
Growth Period ◽  
Carbon Diffusion ◽  
Isothermal Treatment ◽  
Precipitation Process ◽  
Ultra Fast Cooling ◽  
The Matrix

Nanoscale cementite can be obtained in 0.17% carbon steel during isothermal treatment at 500oC after ultra fast cooling (UFC) and thermo-mechanical treatment. The precipitation strengthening contribution to yield strength was more than 250 MPa, when the heat treatment time was less than 20 min. The carbon diffusion is impacted by Mn and Si, which are redistributed during the precipitation process. All the effects induced by substitutional elements can be manifested through the restricted carbon diffusion, which is equal to the carbon diffusion multiplied by adjustable parameters. Based on this, a kinetic model has been adapted to simulate the precipitation behaviors of cementite involving the evolution of the number density per unit volume, radius of cementite over time, and the evolution of carbon concentration in matrix. An excellent agreement in mean radius of particles between the predictions of the model and experimental observations was obtained. It was found that the nucleation period of cementite was very short and did not exceed 0.2 s, and there was an overlap between the nucleation period and the growth period, and the coarsening period began at about 1s. In the growth stage, the carbon concentration in the matrix dropped rapidly and the mean radius of particles increased quickly. In the coarsening stage, the carbon concentration remained unchanged and the number of particles per unit volume fell sharply.

Effects of Carbon Content Change on Growth of Compound Layer in Surface of Nitrided Steel

2021 ◽  
Vol 1016 ◽  
pp. 1510-1514
Author(s):  
Takahide Umehara ◽  
Masato Yuya
Keyword(s):  
Carbon Concentration ◽  
Chemical Potential ◽  
Treatment Time ◽  
Compound Layer ◽  
Iron Nitrides ◽  
Change Over Time ◽  
Nitrided Steel ◽  
The Matrix ◽  
Ε Phase ◽  
Over Time

When steel is nitrided, a compound layer mainly composed of iron nitrides, ε-Fe2~3N and the γ’-Fe4N phase, is formed on the steel surface. It is an extremely important industrial issue to clarify factors governing the formation of the compound layer during nitriding and to establish unified views on the mechanism of compound layer formation. Therefore, in order to clarify the effect of change in carbon concentration on the growth of the ε phase and the γ’ phase in the compound layer on nitrided steel, we evaluated the change over time in the concentration of the alloy elements in the surface layer, and the phases of the compound layer on nitrided steels containing various amount of carbon in the matrix. The results were that the change over time in the carbon concentration in the compound layer was mainly responsible for the change over time in the phases of the compound layer. Furthermore, it was discovered that the change over time in the carbon concentration distribution occurred because both increasing of carbon from the matrix to the compound layer, and decreasing of carbon from the surface of compound layer to the atmosphere. That caused the gradient change of chemical potential of carbon in the through-thickness direction of compound layer, and the phases of the compound layer were changed with the treatment time.

Kinetic Study of the Growth of Hard Layers on a Low Carbon Steel

MRS Advances ◽  
2017 ◽  
Vol 2 (50) ◽  
pp. 2809-2817
Author(s):  
Daniel S. Huerta ◽  
E.D. García Bustos ◽  
D.V. Melo Máximo ◽  
M. Flores Martinez
Keyword(s):  
Carbon Steel ◽  
Treatment Time ◽  
Low Carbon Steel ◽  
Thermochemical Treatment ◽  
Low Carbon ◽  
X Ray Diffraction ◽  
Kinetic Growth ◽  
Steel Aisi ◽  
Growth Constants ◽  
Substrate Hardness

ABSTRACTIn the present work the kinetic growth is analyzed for a hard coating applied on a low carbon steel AISI 8620. A thermochemical treatment of bored with dehydrated paste at temperatures of 900, 950 and 1000 °C with a residence time of 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of the steel were evaluated by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The layer formed has a size of 20 to 113 μm which will be dependent on the process temperature, the treatment time and the alloy elements of the substrate. Hardness of 1493-1852 HV are presented for treatment times and temperatures established in this study. The kinetics of growth were determined and analyzed using a mathematical model of diffusion, evaluating the penetration of the biphasic layer that is determined as a function of the time and temperature of the thermochemical treatment (TCT). The results show the increase in the growth constants (k) with respect to the bored temperatures. The activity energy (Q) of the material AISI 8620 was also obtained.

Corrosion Behavior of Al-Si-Cr-Cu Bearing Low Carbon Steel in A Cyclic Dry/Wet Laboratory Test

2009 ◽  
Vol 79-82 ◽  
pp. 1017-1020 ◽  
Author(s):  
Hui Shu Zhang ◽  
Dong Ping Zhan ◽  
Song Lian Bai ◽  
Zhou Hua Jiang
Keyword(s):  
Carbon Steel ◽  
Electrochemical Impedance ◽  
Low Carbon Steel ◽  
Optical Microscope ◽  
Low Carbon ◽  
Rust Layer ◽  
Electrochemical Behaviors ◽  
Corrosion Rates ◽  
The Matrix ◽  
Corrosion Behaviors

The corrosion behaviors of Al-Si-Cr-Cu bearing low carbon steel and a reference steel Q235 were tested in a cyclic dry/wet environment containing 0.01mol/L NaHSO3 in laboratory. Rust layers were observed by optical microscope (OM), scanning electron microscopy (SEM) and XRD. The electrochemical behaviors of the steels were studied on the polarization curves and electrochemical impedance spectroscopy (EIS). The results indicate that after 120h corrosion test, the annual corrosion rates of the designed steels reduce 42 % than Q235 at least. The corrosion products are generally iron oxyhydroxides and oxides such as FeOOH, γ-FeOOH, α-FeOOH, γ-Fe2O3, Fe3O4. The α-FeOOH possesses good stabilization mainly exits and can improve the corrosion resistance. There are the enrichments of Cu, Cr, Si and Al in the rust layer close to the matrix, which make the rust layer be more compact and protected. The corrosion currents of the two designed steels are lower than that of Q235, the corrosion potentials are higher than that of Q235 after Tafel fitting. The rust layer impedances of the designed steels are higher than that of Q235.

Effect of Heat-Treatment Time on Microstructure and Mechanical Properties of Mg-5Gd-2Y-2Zn-0.5Zr Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1384-1389 ◽  
Author(s):  
Ling Gang Meng ◽  
Can Feng Fang ◽  
Peng Peng ◽  
Nai Pu Li ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Treatment Time ◽  
Time Range ◽  
Lpso Phase ◽  
High Temperature Heat Treatment ◽  
Lpso Structure ◽  
The Matrix ◽  
New Type ◽  
The Stability

Microstructure evolution of Mg-5Gd-2Y-2Zn-0.5Zr alloy during high temperature heat-treatment at 500°C in the time range 10-70h was investigated. The results show that after adding the element Y, the as-cast Mg-5Gd-2Y-2Zn-0.5Zr alloy forms the Mg12Zn(Y,Gd) phase with 18R-LPSO structure at the grain boundary. During heat-treatment at 500°C, the stability of 18R-LPSO structure is weakened by Gd atoms, parts of LPSO phases dissolve gradually into the matrix with time prolonged and a new type Mg(Y,Gd)Zn phase come into being. LPSO phase in the grain boundary can ensure the ultimate tensile strength and elongation of the alloy, and effect of dissevering on the LPSO phase by Mg(Gd,Y)Zn phase results the decrease of UTS and elongation.

Ascorbic acid in the normal and regenerating tail of the house lizard, Hemidactylus flaviviridis

Development ◽  
1971 ◽  
Vol 26 (2) ◽  
pp. 285-293
Author(s):  
R. V. Shah ◽  
P. K. Hiradhar ◽  
D. K. Magon
Keyword(s):  
Wound Healing ◽  
Ascorbic Acid ◽  
Matrix Material ◽  
Growth Period ◽  
Tail Regeneration ◽  
The Matrix ◽  
Metabolic Activities ◽  
Vitamin Level ◽  
Hemidactylus Flaviviridis

The concentration of ascorbic acid (AA) and the histochemical distribution of the vitamin in the normal and regenerating tail of the gekkonid lizard, Hemidactylus flaviviridis, have been investigated. In the regenerating tail of the lizard the AA concentration almost doubles during wound healing and becomes fivefold during differentiation. However, it falls almost to the normal level during the blastema phase (i.e. period between wound healing and differentiation). Again, during the growth period (i.e. after differentiation) the AA concentration gradually becomes reduced, reaching the normal mark as the regenerate regains the full length of the original tail. Nevertheless, the vitamin level does not fall below the normal mark at any stage of regeneration. Increase of ascorbic acid during wound healing is thought to be mainly due to increased demand for the vitamin at the broken ends of the stump tissues, for their repair and formation of wound epithelium; the vitamin is known to help these processes. A fivefold increase of the vitamin during the differentiation period corresponds to an increased pace of laying down of the matrix material for the connective tissues, suggesting the role of ascorbic acid in the formation of collagen and mucopolysaccharides. Besides, the role of ascorbic acid in lipid and carbohydrate metabolism is also important during tail regeneration. Fluctuations in the vitamin level during different phases of tail regeneration are correlated with various states of metabolic activities of the corresponding phases.

Incorporation of Magnetite in Toughened PLA Nanocomposite: Tensile and Thermal Stability

2022 ◽  
Vol 1048 ◽  
pp. 15-20
Author(s):  
Ruey Shan Chen ◽  
Sahrim Ahmad
Keyword(s):  
Thermal Stability ◽  
Tensile Testing ◽  
Treatment Time ◽  
Optimum Distribution ◽  
Melt Compounding ◽  
The Matrix ◽  
Liquid Natural Rubber ◽  
Suitable Treatment ◽  
Ultrasonication Time ◽  
Internal Mixer

In this study, liquid natural rubber (LNR) toughened polylactic acid (PLA) incorporated with magnetite (Fe3O4) nanocomposites were fabricated via melt-compounding in an internal mixer and followed by hot/cold pressing. The effects of ultrasonic treatment time (1-3 hours) and Fe3O4 (0.5-4.0 wt%) nanoparticles loading on tensile, morphology and thermal stability were investigated. Based on tensile testing results, the ultrasonication time of 1 hour was served as the most suitable treatment period to achieve the optimum distribution of Fe3O4 within PLA/LNR matrix. Among the investigated nanoparticles loading, 1 wt% Fe3O4 nanocomposite presented the highest tensile strength of 23.7 MPa, Young’s modulus of 1293.5 MPa and strain at break of 2.8%. SEM micrographs showed that the over-treated nanocomposites with 2-3 hours and over-high nanoparticles loading had resulted in the formation of clusters in the matrix. With increasing Fe3O4 loading, the decomposition of PLA/LNR nanocomposites was initiated earlier.

scholarly journals Effect of Heat Treatment on the Microstructure and Corrosion Resistance of Stainless/Carbon Steel Bimetal Plate

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Hao Li ◽  
Liyuan Zhang ◽  
Boyang Zhang ◽  
Qingdong Zhang
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Carbon Content ◽  
Carbon Diffusion ◽  
Annealing Process ◽  
Stainless Steel Surface ◽  
Surface Corrosion ◽  
Annealing Conditions

In order to research the effect of heat treatment on the microstructure and corrosion resistance of stainless/carbon steel bimetal plate, the annealing process at 700°C with different times was carried out for stainless/carbon steel bimetal plate. Because the carbon content of carbon steel was higher than that of stainless steel, the carbon would diffuse from carbon steel to stainless steel in the bimetal plate during the annealing process. The carbon diffusion would cause the thickness of the decarburized layer in carbon steel and the carbon content of stainless steel to increase. The carbon diffusion would be ongoing with the annealing process until the carbon content of stainless steel reached 0.08%. The higher carbon content could help in the formation of more chromium-depleted regions in the stainless steel surface, causing the stainless steel in the bimetal plate to have a poorer surface corrosion resistance than that of stainless steel under the same annealing conditions.

Crystal structural and diffusion property in titanium carbides: A molecular dynamics study

2016 ◽  
Vol 30 (26) ◽  
pp. 1650334 ◽  
Author(s):  
Yanan Lv ◽  
Weimin Gao
Keyword(s):  
Molecular Dynamics ◽  
Carbon Concentration ◽  
Carbon Diffusion ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Structure Variation ◽  
Atomic Structures ◽  
Text Structures ◽  
Atomic Exchange ◽  
Titanium Carbides

Titanium carbides were studied via molecular dynamics simulation to characterize TiC[Formula: see text] structures with respect to the carbon diffusion properties in this study. The effect of carbon concentration on atomic structures of titanium carbides was investigated through discussing the structure variation and the radial distribution functions of carbon atoms in titanium carbides. The carbon diffusion in titanium carbides was also analyzed, focusing on the dependence on carbon concentration and carbide structure. Carbon diffusivity with different carbon concentrations was determined by molecular dynamics (MD) calculations and compared with the available experimental data. The simulation results showed an atomic exchange mechanism for carbon diffusion in titanium carbide.

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