scholarly journals Effect of Deformation Structure and Annealing Temperature on Corrosion of Ultrafine-Grain Fe-Cr Alloy Prepared by Equal Channel Angular Pressing

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Muhammad Rifai ◽  
Motohiro Yuasa ◽  
Hiroyuki Miyamoto
Keyword(s):  
Grain Boundaries ◽  
Equal Channel Angular Pressing ◽  
Annealing Temperature ◽  
Surface Region ◽  
Passivation Layer ◽  
Ultrafine Grain ◽  
Deformation Structure ◽  
Early Stages ◽  
Angular Pressing ◽  
The Stability

The effect of the deformation structure and annealing temperature on the corrosion of ultrafine-grain (UFG) Fe-Cr alloys with 8 to 12% Cr prepared by equal channel angular pressing (ECAP) was investigated with particular emphasis on the stability of the passivation layer. Fe-Cr alloys were processed by ECAP using up to eight passes at 423 K by the Bc route, followed by annealing at temperatures of 473 to 1173 K for 1 h. Passivity appeared in all alloys as a result of ECAP, and the stability of the passivation layer was evaluated by anodic polarization measurements in a 1000 mol·m−3 NaCl solution. The stability of the passivation layer increased as the degree of deformation became more extensive with successive ECAP passes, and distinct escalation occurred with the formation of a UFG microstructure. In the early stages of annealing at moderate temperatures, the stability of the passivation layer deteriorated, although no visible grain growth occurred, and this effect increased monotonically with increasing annealing temperature. The high degree of stability of the passivation layer on UFG alloys following ECAP can be attributed to the large number of high-angle nonequilibrium grain boundaries, which may lead to Cr enrichment of the surface region. The deterioration of the passivation layer in the early stages of annealing may be attributed to a change in the grain boundaries to an equilibrium state. The present results show that the superiority of as-ECAPed materials of the Fe-Cr alloy to recovered ones by heat treatment can be achieved with 8–10% Cr as observed in 20% Cr.

Grain Boundary Diffusion in Recrystallizing Nanocrystalline Materials

2009 ◽  
Vol 289-292 ◽  
pp. 641-648 ◽  
Author(s):  
Leonid Klinger ◽  
Y. Amouyal ◽  
Sergiy V. Divinski ◽  
Eugen Rabkin
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Equal Channel Angular Pressing ◽  
Diffusion Coefficients ◽  
Nanocrystalline Materials ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Ultrafine Grain ◽  
Angular Pressing

A model that considers diffusion in nanocrystalline materials undergoing recrystallization was developed. Application of this model enabled us deriving 63Ni radiotracer diffusion coefficients along the grain boundaries in ultrafine grain copper produced by equal channel angular pressing from the experimentally measured radiotracer penetration profiles.

Deformation Structure and Crystal Orientation of Copper Single Crystals Deformed by Equal Channel Angular Pressing

2003 ◽  
Vol 426-432 ◽  
pp. 2795-2800 ◽  
Author(s):  
Hiroyuki Miyamoto ◽  
Uwe Erb ◽  
Tetsuo Koyama ◽  
Takura Mimaki ◽  
Alexei Vinogradov ◽  
...  
Keyword(s):  
Single Crystals ◽  
Equal Channel Angular Pressing ◽  
Crystal Orientation ◽  
Deformation Structure ◽  
Angular Pressing ◽  
Copper Single Crystals

Influence of Crystallite Size on Consolidation of Carbon Nanotube Reinforced AA 4032 Composite Powders by Equal Channel Angular Pressing

2011 ◽  
Vol 471-472 ◽  
pp. 127-132
Author(s):  
M.S. Senthil Saravanan ◽  
K. Sivaprasad ◽  
S.P. Kumaresh Babu
Keyword(s):  
Crystallite Size ◽  
Equal Channel Angular Pressing ◽  
Ultrafine Grain ◽  
Electron Microscopic ◽  
Composite Powders ◽  
Powder Consolidation ◽  
Angular Pressing ◽  
Grain Structures ◽  
Transmission Electron ◽  
The One

Equal channel angular pressing (ECAP) is the one of the promising methods of severe plastic deformation to obtain bulk ultrafine grain structures. However, ECAP can also be used for powder consolidation. In the present study, fully dense bulk AA 4032 alloy was consolidated from nanocrystalline and microcrystalline powders. These materials were processed by ECAP until four passes at ambient temperature. It is observed that hardness and densification increased significantly with increase in number of ECAP passes. Transmission electron microscopic and scanning electron microscopic examinations evidenced that crystallite size of the nanopowders are unaltered, however a significant crystallite size reduction from around 50 µm down to submicron size is observed. Moreover, higher densification is achieved in microcrystalline powders than nano powders, whereas higher hardness in the case of nanopowders compared to microcrystalline powders.

scholarly journals A Coupled EBSD/TEM Analysis of the Microstructure Evolution of a Gradient Nanostructured Ferritic/Martensitic Steel Subjected to Surface Mechanical Attrition Treatment

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 140 ◽  
Author(s):  
Wenbo Liu ◽  
Xiao Jin ◽  
Bo Zhang ◽  
Di Yun ◽  
Piheng Chen
Keyword(s):  
Grain Boundaries ◽  
Transition Zone ◽  
Microstructure Evolution ◽  
Electron Backscatter Diffraction ◽  
Surface Region ◽  
Surface Mechanical Attrition Treatment ◽  
Ultrafine Grain ◽  
Tem Analysis ◽  
Mechanical Attrition ◽  
Rafm Steel

Surface mechanical attrition treatment (SMAT) was performed on a reduced ferritic/martensitic (RAFM) steel to form a nanostructured (NS) layer on the surface of the sample. Both electron backscatter diffraction (EBSD) and TEM were used to investigate the microstructure evolution during SMAT. The experimental results showed that there were three different zones after SMAT: (i) The “ultrafine grain” (UFG) zone, observed at the top-most surface region, (ii) the “transition zone” in which the original grains were fragmented under the severe plastic deformation and (iii) the “deformed zone” in which the original grains were simply deformed. The average grain sizes increased rapidly with the increase of depth, while the Vickers hardness decreased with the increase of depth, and this phenomenon could be explained in terms of boundary strengthening and dislocation strengthening. The number fractions of medium-angle grain boundaries (MAGBs) and medium-high-angle grain boundaries (MHAGBs) in UFG zones were larger than those in the transition zone and the deformed zone. However, the number fraction of the low-angle grain boundaries (LAGBs) was extremely small in all the zones after SMAT, especially in the transition zone.

scholarly journals Effect of warm equal channel angular pressing on the structure and mechanical properties of Ti0.16Pd0.14Fe (wt%) alloy

2019 ◽  
Vol 58 (1) ◽  
pp. 22-31
Author(s):  
Victor Grishkov ◽  
Vladimir Kopylov ◽  
Alexander Lotkov ◽  
Svetlana Latushkina ◽  
Anatoly Baturin ◽  
...  
Keyword(s):  
Phase Composition ◽  
Grain Boundaries ◽  
Equal Channel Angular Pressing ◽  
Initial Value ◽  
Initial Strength ◽  
Torsional Strain ◽  
Angular Pressing ◽  
Initial Alloy ◽  
Average Grain Size ◽  
Before And After

Abstract Here we analyze the microstructure and phase composition of a Ti alloy with 0.16Pd and 0.14Fe (wt%) alloy exposed to warm equal channel angular pressing (ECAP) at 648 K. The analysis shows that after four ECAP passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP. The initial alloy reveals a high content of Fe and Pd atoms near grain boundaries compared to central grain regions. Such near-boundary zones contain orthorhombic α′′ martensite in addition to the α phase, and β or α + β particles are found directly at the grain boundaries. These features of the phase composition are inherited after ECAP. The yield strength of the ECAP treated alloy is 500 MPa, being greater than the initial strength 350 MPa, and its margin of plasticity is rather high. The torsional strain up to fracture in the initial and in the ECAP treated alloy is 70% and 50%, respectively.

Grain Boundary Radiotracer Diffusion of Ni in Ultra-Fine Grained Cu and Cu - 1wt.% Pb Alloy Produced by Equal Channel Angular Pressing

2008 ◽  
Vol 584-586 ◽  
pp. 380-386 ◽  
Author(s):  
Jens Ribbe ◽  
Guido Schmitz ◽  
Y. Amouyal ◽  
Yuri Estrin ◽  
Sergiy V. Divinski
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Equal Channel Angular Pressing ◽  
Boundary Diffusion ◽  
Ion Beam ◽  
Short Circuit ◽  
Grain Boundary Diffusion ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Diffusion Paths

The radiotracer technique was applied for measuring grain boundary diffusion of Ni in ultrafine grained (UFG) copper materials with different nominal purities and in a Cu—1wt.%Pb alloy. The UFG specimens were prepared by equal channel angular pressing at room temperature. The stability of the microstructure was studied by focused ion beam imaging. Grain boundary diffusion of the 63Ni radioisotope was investigated in the temperature interval from 293 to 490K under the formal Harrison type C kinetic conditions. Two distinct short-circuit diffusion paths were observed. The first (relatively slow) path in the UFG materials corresponds unambiguously to relaxed high-angle grain boundaries with diffusivities which are quite similar to those in the respective coarse-grained reference materials. The second path is characterized by significantly higher diffusivities. The experimental data are discussed to elucidate the contribution of nonequilibrium grain boundaries in the deformed materials. Alternative contributions of other shortcircuit diffusion paths cannot be ruled out, particularly for the Cu-Pd alloy.

Investigation of Tensile Property and Pore Closure Behavior and the Influence of Processing Route during Equal Channel Angular Pressing of Pure Aluminum Powder Compacts

2014 ◽  
Vol 592-594 ◽  
pp. 444-450 ◽  
Author(s):  
R. Venkatraman ◽  
S. Raghuraman ◽  
R. Balaji ◽  
Kumar K.S. Ajay ◽  
M. Viswanath
Keyword(s):  
Equal Channel Angular Pressing ◽  
Cell Structure ◽  
Pure Aluminum ◽  
Dislocation Cell ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Processing Route ◽  
Angular Pressing ◽  
Ecap Process ◽  
Pore Closure

This paper revolves around the idea of finding the strength enhancement of pure ‘Al’ compacts processed through Equal-Channel Angular Pressing (ECAP) process which ultimately results in fine grain structure of the material processed. The material initially prepared through conventional powder metallurgical route is processed in an ECAP die with a channel angle of 1100. The tensile test and micro-structural evaluation is done following the ECAP process and it is found that there was a substantial enhancement in the tensile properties and Ultrafine Grain (UFG) structure is obtained due to the Severe Plastic Deformation (SPD) phenomenon taking place during the process. The pore closure behavior is also analyzed using the TEM micrographs after each pass in ECAP die and promising results are obtained when the material is processed through different routes. The dislocation cell structure is also found to get refined after each pass through the die. The pore closure behavior is also confirmed using the DEFORM 3D software when the aluminum is simulated under similar conditions.

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