Grain-size dependence of plastic deformation in nanocrystalline Fe

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

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Finite element modelling of microstructural changes during equal channel angular drawing of pure aluminium

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-021-06972-0 ◽

2021 ◽

Author(s):

Serafino Caruso ◽

Stano Imbrogno

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Finite Element ◽

Size Variation ◽

Fe Model ◽

Pure Aluminium ◽

Continuous Dynamic Recrystallization ◽

Research Activities ◽

Hardness Change ◽

Continuous Dynamic

AbstractGrain refinement by severe plastic deformation (SPD) techniques, as a mechanism to control microstructure (recrystallization, grain size changes,…) and mechanical properties (yield strength, ultimate tensile strength, strain, hardness variation…) of pure aluminium conductor wires, is a topic of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model able to describe the microstructural evolution and the continuous dynamic recrystallization (CDRX) that occur during equal channel angular drawing (ECAD) of commercial 1370 pure aluminium (99.7% Al). A user subroutine has been developed based on the continuum mechanical model and the Hall-Petch (H-P) equations to predict grain size variation and hardness change. The model is validated by comparison with the experimental results and a predictive analysis is conducted varying the channel die angles. The study provides an accurate prediction of both the thermo-mechanical and the microstructural phenomena that occur during the process characterized by large plastic deformation.

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Size-Dependence of Photoluminescence Property of ZnO Nanoparticles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.887-888.143 ◽

2014 ◽

Vol 887-888 ◽

pp. 143-146 ◽

Cited By ~ 2

Author(s):

Xiao Fang Wang ◽

Yun Liang Fang ◽

Tian Le Li ◽

Fu Juan Wang

Keyword(s):

Grain Size ◽

Lower Energy ◽

Size Dependence ◽

Surface States ◽

Photoluminescence Property ◽

Precipitation Method ◽

Pl Spectra ◽

Broadband Emission ◽

Band Emission ◽

20 Nm

Nanometer-sized ZnO crystals with the diameter from 20 nm to 110 nm were prepared by homogenous precipitation method (HPM). The photoluminescence (PL) spectra of as-prepared nanoparticles under excitation at the wavelength of 320 nm were detected. The PL spectra were fitted with Gaussian curves, in which a good fitting consisting of six Gaussian peaks was obtained. We observed that the multi-peak centers do not change much, while the relative amplitude of Gaussian combination to the band-to-band emission decreases rapidly with the increased grain size. It shows that the broadband emission at the lower energy is associated with the surface states.

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Computation on continuous grain refinement in AA1050 aluminum during repetitive tube expansion and shrinking technique

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420715625086 ◽

2015 ◽

Vol 232 (4) ◽

pp. 307-318

Author(s):

H Jafarzadeh ◽

K Abrinia

Keyword(s):

Finite Element Method ◽

Plastic Deformation ◽

Grain Size ◽

Finite Element ◽

Dislocation Density ◽

Severe Plastic Deformation ◽

Grain Refinement ◽

Half Cycle ◽

Tube Expansion ◽

Element Method

The microstructure evolution during recently developed severe plastic deformation method named repetitive tube expansion and shrinking of commercially pure AA1050 aluminum tubes has been studied in this paper. The behavior of the material under repetitive tube expansion and shrinking including grain size and dislocation density was simulated using the finite element method. The continuous dynamic recrystallization of AA1050 during severe plastic deformation was considered as the main grain refinement mechanism in micromechanical constitutive model. Also, the flow stress of material in macroscopic scale is related to microstructure quantities. This is in contrast to the previous approaches in finite element method simulations of severe plastic deformation methods where the microstructure parameters such as grain size were not considered at all. The grain size and dislocation density data were obtained during the simulation of the first and second half-cycles of repetitive tube expansion and shrinking, and good agreement with experimental data was observed. The finite element method simulated grain refinement behavior is consistent with the experimentally obtained results, where the rapid decrease of the grain size occurred during the first half-cycle and slowed down from the second half-cycle onwards. Calculations indicated a uniform distribution of grain size and dislocation density along the tube length but a non-uniform distribution along the tube thickness. The distribution characteristics of grain size, dislocation density, hardness, and effective plastic strain were consistent with each other.

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The grain size dependence of flow stress in a Cu–26Ni–17Zn alloy

Acta Materialia ◽

10.1016/s1359-6454(99)00464-4 ◽

2000 ◽

Vol 48 (8) ◽

pp. 1807-1813 ◽

Cited By ~ 19

Author(s):

S. Nagarjuna ◽

M. Srinivas ◽

K.K. Sharma

Keyword(s):

Grain Size ◽

Flow Stress ◽

Size Dependence

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Simulation of Grain Growth of Materials Produced by Severe Plastic Deformation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.409.597 ◽

2011 ◽

Vol 409 ◽

pp. 597-602

Author(s):

Yuichi Mizuno ◽

Kenji Okushiro ◽

Yoshiyuki Saito

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Dislocation Density ◽

Severe Plastic Deformation ◽

Size Distribution ◽

Grain Size Distribution ◽

Boundary Migration ◽

Interface Energy ◽

Diffusion Reaction ◽

Field Methods

Grain boundary migration in materials under severe plastic deformation was simulated by the phase field methods. The interface energy and dislocation density on growth kinetics were simulated on systems of 2-dimensional lattice. .In inhomogeneous systems grain size distributions in simulated grain structures were binodal distributions. The classification of the solution of differential equations based on the mean-field Hillert model describing temporal evolution of the scaled grain size distribution function was in good agreement with those given by the Computer simulations. Effect of dislocation on thermodynamic stability was taken into consideration. Dislocation density distribution was calculated by a equation based on the diffusion-reaction equation.. Scaled grain size distribution was known to be affected by the dislocation.

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A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

Journal of Metallurgy ◽

10.1155/2010/647198 ◽

2010 ◽

Vol 2010 ◽

pp. 1-16 ◽

Cited By ~ 36

Author(s):

Yngve Bergström ◽

Ylva Granbom ◽

Dirk Sterkenburg

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Deformation Process ◽

Volume Fraction ◽

High Energy ◽

Martensite Content ◽

Plastic Deformation Process ◽

Deformation Hardening ◽

Dp Steels ◽

Ferrite Grain Size

A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

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