Three-dimensional atom probe analysis of boron segregation at austenite grain boundary in a low carbon steel - Effects of boundary misorientation and quenching temperature

2018 ◽  
Vol 154 ◽  
pp. 168-171 ◽  
Author(s):  
Goro Miyamoto ◽  
Ai Goto ◽  
Naoki Takayama ◽  
Tadashi Furuhara
Keyword(s):  
Carbon Steel ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Atom Probe ◽  
Low Carbon ◽  
Boundary Misorientation ◽  
Quenching Temperature ◽  
Boron Segregation ◽  
Austenite Grain ◽  
Austenite Grain Boundary

scholarly journals Anisotropic Pinning-Effect of Inclusions in Mg-Based Low-Carbon Steel

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2241
Author(s):  
Chi-Kang Lin ◽  
Hsuan-Hao Lai ◽  
Yen-Hao Su ◽  
Guan-Ru Lin ◽  
Weng-Sing Hwang ◽  
...  
Keyword(s):  
Grain Size ◽  
Carbon Steel ◽  
Grain Boundary ◽  
Low Carbon Steel ◽  
In Situ Observation ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grain Boundary

In this study, the effect of austenite grain size on acicular ferrite (AF) nucleation in low-carbon steel containing 13 ppm Mg is determined. The average austenite grain size was calculated using OM Leica software. Results show that the predicted and experimental values of austenite grain size are extremely close, with a deviation of less than 20 µm. AF formation is difficult to induce by either excessively small and large austenite grain sizes; that is, an optimal austenite grain size is required to promote AF nucleation probability. The austenite grain size of 164 µm revealed the highest capacity to induce AF formation. The effects of the maximum distance of carbon diffusion and austenite grain size on the microstructure of Mg-containing low carbon steel are also discussed. Next, the pinning ability of different inclusion types in low-carbon steel containing 22 Mg is determined. The in situ observation shows that not every inclusion could inhibit austenite grain migration; the inclusion type influences pinning ability. The grain mobility of each inclusion was calculated using in situ micrographs of confocal scanning laser microscopy (CSLM) for micro-analysis. Results show that the austenite grain boundary can strongly be pinned by Mg-based inclusions. MnS inclusions are the least effective in pinning austenite grain boundary migration.

scholarly journals Effect of Austenitization Conditions on the Transformation Behavior of Low Carbon Steel Containing Ti–Ca Oxide Particles

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1070 ◽  
Author(s):  
Chao Wang ◽  
Xin Wang ◽  
Jian Kang ◽  
Guo Yuan ◽  
Guodong Wang
Keyword(s):  
Grain Size ◽  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Austenitizing Temperature ◽  
Austenite Grain Size ◽  
Boron Segregation ◽  
Austenite Grain ◽  
Mn Diffusion ◽  
Oxide Particles

Inclusion-induced acicular ferrite (AF) nucleation has been used for microstructure refinement in steel. Austenitization conditions have a significant influence on AF nucleation ability. In this paper, the effects of austenitization temperature and holding time on the transformation behaviors of low carbon steel containing Ti–Ca oxide particles were studied. A thermal treatment experiment, high temperature in situ observation, and calculation of Mn diffusion were carried out. The results indicate that small austenite grain size under low austenitizing temperature promoted grain boundary reaction products. With an increase in austenitizing temperature, the nucleation sites transferred to intragranular particles and AF transformation was improved. The inclusion particles in the Ti–Ca deoxidized steel were featured by an oxide core rich in Ti and a lesser amount of Ca and with MnS precipitation on the local surface, which showed a strong ability to promote AF nucleation. At a low austenitizing temperature, Mn diffusion was limited and the development of Mn-depleted zones (MDZs) around inclusions was not sufficient. The higher diffusion capacity of Mn at a high austenitizing temperature promoted the formation of MDZs to a larger degree and increased the AF nucleation ability. Boron segregation at large-sized austenite grain boundaries played an important role in AF transformation. Austenite grain size, Mn-depleted zone development, and boron segregation at grain boundaries were the decisive factors influencing the transformation behaviors under different austenitization conditions for the test steel.

The Effect of Severe Plastic Deformation on the Brittle-Ductile Transition in Low Carbon Steel

2009 ◽  
Vol 633-634 ◽  
pp. 471-480
Author(s):  
Masaki Tanaka ◽  
Kenji Higashida ◽  
Tomotsugu Shimokawa
Keyword(s):  
Fracture Toughness ◽  
Carbon Steel ◽  
Grain Boundaries ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Dislocation Dynamics ◽  
Strain Rates ◽  
Low Carbon ◽  
Dislocation Source ◽  
Brittle Ductile Transition

Brittle-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various temperatures and strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the controlling process of the BDT was not changed by the deformation with the ARB process. It was deduced that the decrease in the BDT temperature by grain refining was not due to the increase in the dislocation mobility controlled by short-range barriers. Quasi-three-dimensional simulations of dislocation dynamics, taking into account of crack tip shielding due to dislocations, were performed to investigate the effect of a dislocation source spacing along a crack front on the BDT. The simulation indicated that the BDT temperature is decreased with decreasing in the dislocation source spacing. Molecular dynamics simulations revealed that moving dislocations were impinged against grain boundaries and were reemitted from there with increasing strain. It indicates that grain boundaries can be new sources in ultra-fine grained materials, which increases toughness at low temperatures.

Modeling austenite–ferrite transformation in low carbon steel using the cellular automaton method

2004 ◽  
Vol 19 (10) ◽  
pp. 2877-2886 ◽  
Author(s):  
Y.J. Lan ◽  
D.Z. Li ◽  
Y.Y. Li
Keyword(s):  
Carbon Steel ◽  
Cellular Automaton ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Low Carbon Steel ◽  
Carbon Diffusion ◽  
Cellular Automaton Model ◽  
Low Carbon ◽  
Austenite Grain ◽  
Ferrite Transformation

Austenite–ferrite transformation at different isothermal temperatures in low carbon steel was investigated by a two-dimensional cellular automaton approach, which provides a simple solution for the difficult moving boundary problem that governs the ferrite grain growth. In this paper, a classical model for ferrite nucleation at austenite grain boundaries is adopted, and the kinetics of ferrite grain growth is numerically resolved by coupling carbon diffusion process in austenite and austenite–ferrite (γ–α) interface dynamics. The simulated morphology of ferrite grains shows that the γ–α interface is stable. In this cellular automaton model, the γ–α interface mobility and carbon diffusion rate at austenite grain boundaries are assumed to be higher than those in austenite grain interiors. This has influence on the morphology of ferrite grains. Finally, the modeled ferrite transformation kinetics at different isothermal temperatures is compared with the experiments in the literature and the grid size effects of simulated results are investigated by changing the cell length of cellular automaton model in a set of calculations.

scholarly journals Three-dimensional Observation of Ferrite Plate in Low Carbon Steel Weld

2005 ◽  
Vol 45 (5) ◽  
pp. 756-762 ◽  
Author(s):  
M. ENOMOTO ◽  
K. M. WU ◽  
Y. INAGAWA ◽  
T. MURAKAMI ◽  
S. NANBA
Keyword(s):  
Carbon Steel ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Steel Weld ◽  
Low Carbon ◽  
Ferrite Plate
Sign in / Sign up

Export Citation Format

Share Document