Effect of initial dislocation density on hydrogen accumulation behavior in martensitic steel

2020 ◽  
Vol 178 ◽  
pp. 318-323 ◽  
Author(s):  
Yuji Momotani ◽  
Akinobu Shibata ◽  
Takashi Yonemura ◽  
Yu Bai ◽  
Nobuhiro Tsuji
Keyword(s):  
Dislocation Density ◽  
Martensitic Steel ◽  
Initial Dislocation Density ◽  
Hydrogen Accumulation ◽  
Accumulation Behavior

scholarly journals Relation between Sub-grain Size and Dislocation Density During Steady-State Dislocation Creep of Polycrystalline Cubic Metals

2018 ◽  
Vol 7 (4) ◽  
pp. 26 ◽  
Author(s):  
Manabu Tamura
Keyword(s):  
Grain Size ◽  
Steady State ◽  
Dislocation Density ◽  
Martensitic Steel ◽  
Empirical Relation ◽  
Dislocation Creep ◽  
Theoretical Relation ◽  
Cross Sectional ◽  
Cubic Metals ◽  
Polycrystalline Metals

The sub-grain size, d, during steady-state dislocation creep of polycrystalline metals is theoretically formulated to be inversely proportional to the dislocation density, ρ, which is defined as the number of dislocations swept out of a sub-grain divided by the cross-sectional area of the sub-grain. This dislocation density differs from the typically observed dislocation density inside a sub-grain after unloading, ρ_ob. In the current work, the ρ_ob values inside sub-grains in steadily crept specimens of Al, Cu, Fe, Fe–Mo alloy, austenitic stainless steel, and high-Cr martensitic steel reported in the literature were used to evaluate the relation ρ_ob=ηρ. It was confirmed that η≈1 for pure metals (regardless of the type of metal) crept at high temperatures and low stresses or for long durations and η>1 for Mo-containing alloys and martensitic steel crept at low temperatures and/or high stresses. Moreover, it is suggested that the condition η>1 corresponds to a state of excess immobile dislocations inside the sub-grain. The theoretical relation d_ob (≈d)∝η∙〖ρ_ob〗^(-1), where d_ob is the observed sub-grain size, essentially differs from the well-known empirical relation d_ob∝〖ρ_ob〗^(-0.5).

scholarly journals Prediction of the Maximum Dislocation Density in Lath Martensitic Steel by Elasto-Plastic Phase-Field Method

2012 ◽  
Vol 53 (9) ◽  
pp. 1598-1603 ◽  
Author(s):  
Zhenhua Cong ◽  
Yoshinori Murata ◽  
Yuhki Tsukada ◽  
Toshiyuki Koyama
Keyword(s):  
Dislocation Density ◽  
Phase Field ◽  
Martensitic Steel ◽  
Field Method ◽  
Phase Field Method ◽  
Plastic Phase

Influence of Initial Defects on the Mechanical Properties of Single Crystal Copper: Discrete Dislocation Dynamics Study

2018 ◽  
Vol 913 ◽  
pp. 627-635
Author(s):  
Ming Yi Zhang ◽  
Min Zhong ◽  
Shuai Yuan ◽  
Jing Song Bai ◽  
Ping Li
Keyword(s):  
Dislocation Density ◽  
Single Crystal ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Single Crystal Copper ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Stress Curve ◽  
Initial Dislocation Density

In this paper, three dimensional discrete dislocation dynamics method was used to quantitatively investigate the influence of initial defects on mechanical response of single crystal copper. Both the irradiation defects (interstitial loops) and random dislocation lines with different densities are considered. The simulation results demonstrate that the yield strength of single crystal copper is higher with higher initial dislocation density and higher interstitial loop density. Dislocation density increases quickly by nucleation and multiplication and microbands are formed during plastic deformation when only the random dislocation lines are initially considered. Characteristics of microbands show excellent agreement with experiment results. Dislocation multiplication is suppressed in the presence of interstitial loops, and junctions and locks between dislocations and interstitial loops are formed. Dislocation density evolution shows fluctuation accompanied with strain-stress curve fluctuation.

Determination of Dislocation Density in Lath Martensite by Means of Electron Backscatter Diffraction

2017 ◽  
Vol 885 ◽  
pp. 275-279 ◽  
Author(s):  
Péter János Szabó ◽  
András Csóré
Keyword(s):  
Dislocation Density ◽  
Martensitic Steel ◽  
Electron Backscatter Diffraction ◽  
Lath Martensite ◽  
Electron Backscatter ◽  
Density Values ◽  
Cold Rolled ◽  
Backscatter Diffraction ◽  
Scanning Electron

As a novel procedure for determining dislocation density, a software was improved with which data obtained by Scanning Electron Microscope (SEM) measurements can be collected and the value of superficial dislocation density can be calculated. Applying this method we investigated cold rolled lath martensitic steel samples. Besides dislocation density values, microstructure mapped by Electron Backscatter Diffraction (EBSD) will be discussed.

Sub-Grain Size and Hall-Petch Relation in Pure Copper Single Crystals

2007 ◽  
Vol 345-346 ◽  
pp. 29-32
Author(s):  
Sei Miura ◽  
Yoshito Nishimura ◽  
Nagato Ono
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Single Crystals ◽  
Pure Copper ◽  
Petch Relation ◽  
Low Dislocation Density ◽  
Initial Dislocation Density ◽  
Bridgeman Method ◽  
Copper Single Crystals ◽  
Critical Resolved Shear Stress

The effect of sub-grain on the yield stress of pure copper single crystals with the [253] orientation was investigated by using the etch pit technique. The single crystal plates were successfully prepared from the seed crystals, which were produced at the melting temperature of 1473 K by the Bridgeman method. The present investigation confirmed the Hall-Petch relation concerning the effect of sub-grain boundaries on the macroscopic yielding of pure copper. The result derived from the extrapolation of the relationship of critical resolved shear stress (CRSS) and the initial dislocation density and sub-grain size is in good agreement with the evaluation in high purity copper single crystals of low dislocation density.

The Constitutive Equation for Silicon and Its Use in Crystal Growth Modeling

1990 ◽  
Vol 112 (2) ◽  
pp. 183-187 ◽  
Author(s):  
C. T. Tsai ◽  
O. W. Dillon ◽  
R. J. De Angelis
Keyword(s):  
Crystal Growth ◽  
Dislocation Density ◽  
Constitutive Equation ◽  
Constitutive Model ◽  
Material Model ◽  
Internal Variable ◽  
Dislocation Motion ◽  
Silicon Crystals ◽  
Initial Dislocation Density ◽  
Temperature Strain

A stress analysis that describes the crystal growing process requires a material model that is valid over a wide temperature range and includes dislocation motion and multiplication. The stresses developed in the growing process could induce residual stresses, changes in dislocation density and buckling into the growing crystals. The dislocation density is introduced as an internal variable in the constitutive model. The stress-strain and dislocation density-strain characteristics of silicon crystals are discussed as a function of temperature, strain rate, and initial dislocation density.

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