scholarly journals The Annealing Twins of Fe-20Mn-4Al-0.3C Austenitic Steels during Symmetric and Asymmetric Hot Rolling

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 882 ◽  
Author(s):  
Changsheng Li ◽  
Biao Ma ◽  
Yanlei Song ◽  
Kun Li ◽  
Jingbo Dong
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Hot Rolling ◽  
High Density ◽  
Annealing Twin ◽  
Austenitic Steels ◽  
Average Grain Size ◽  
Annealing Twins ◽  
Asymmetric Hot Rolling

The present work investigates the annealing twins of Fe-20Mn-4Al-0.3C austenitic steels in symmetric hot rolling (SHR) and asymmetric hot rolling (ASHR). The average grain size is 26 (±9.6) μm and 11 (±7.0) μm for the tested steel in SHR and ASHR processes. The density of high angle grain boundary (HAGB) and annealing twin boundary increase with the decrease of grain size. The annealing twin is obviously higher in ASHR than in SHR. The linear relation model between the logarithm of twin boundary density and the logarithm of the grain size is established. The grain boundary migration is continuously generated during recrystallization in SHR process. The coincident site lattice (CSL) boundary proportion increases with local grain boundary continuing bugling and the migration direction of bugling grain boundary constantly changes. The tensile property of the tested steel is improved due to the effective grain refinement and high density of annealing twins caused by the severe strain in the ASHR process. The purpose of high density HAGB for austenitic steels is helpful to an improvement in mechanical properties.

scholarly journals Experimental and Numerical Investigation of the ECAP Processed Copper: Microstructural Evolution, Crystallographic Texture and Hardness Homogeneity

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 607
Author(s):  
A. I. Alateyah ◽  
Mohamed M. Z. Ahmed ◽  
Yasser Zedan ◽  
H. Abd El-Hafez ◽  
Majed O. Alawad ◽  
...  
Keyword(s):  
Grain Size ◽  
Equal Channel Angular Pressing ◽  
Cross Section ◽  
Room Temperature ◽  
Pure Copper ◽  
High Density ◽  
Ecap Processing ◽  
Heterogeneous Distribution ◽  
Angular Pressing ◽  
Average Grain Size

The current study presents a detailed investigation for the equal channel angular pressing of pure copper through two regimes. The first was equal channel angular pressing (ECAP) processing at room temperature and the second was ECAP processing at 200 °C for up to 4-passes of route Bc. The grain structure and texture was investigated using electron back scattering diffraction (EBSD) across the whole sample cross-section and also the hardness and the tensile properties. The microstructure obtained after 1-pass at room temperature revealed finer equiaxed grains of about 3.89 µm down to submicrons with a high density of twin compared to the starting material. Additionally, a notable increase in the low angle grain boundaries (LAGBs) density was observed. This microstructure was found to be homogenous through the sample cross section. Further straining up to 2-passes showed a significant reduction of the average grain size to 2.97 µm with observable heterogeneous distribution of grains size. On the other hand, increasing the strain up to 4-passes enhanced the homogeneity of grain size distribution. The texture after 4-passes resembled the simple shear texture with about 7 times random. Conducting the ECAP processing at 200 °C resulted in a severely deformed microstructure with the highest fraction of submicron grains and high density of substructures was also observed. ECAP processing through 4-passes at room temperature experienced a significant increase in both hardness and tensile strength up to 180% and 124%, respectively.

scholarly journals Dislocations in Grain Boundary Regions: The Origin of Heterogeneous Microstrains in Nanocrystalline Materials

2019 ◽  
Vol 51 (1) ◽  
pp. 513-530 ◽  
Author(s):  
Zhenbo Zhang ◽  
Éva Ódor ◽  
Diana Farkas ◽  
Bertalan Jóni ◽  
Gábor Ribárik ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Md Simulation ◽  
High Pressure Torsion ◽  
Md Simulations ◽  
Line Profile Analysis ◽  
Misfit Dislocations ◽  
X Ray ◽  
Average Grain Size

Abstract Nanocrystalline materials reveal excellent mechanical properties but the mechanism by which they deform is still debated. X-ray line broadening indicates the presence of large heterogeneous strains even when the average grain size is smaller than 10 nm. Although the primary sources of heterogeneous strains are dislocations, their direct observation in nanocrystalline materials is challenging. In order to identify the source of heterogeneous strains in nanocrystalline materials, we prepared Pd-10 pct Au specimens by inert gas condensation and applied high-pressure torsion (HPT) up to γ ≅ 21. High-resolution transmission electron microscopy (HRTEM) and molecular dynamic (MD) simulations are used to investigate the dislocation structure in the grain interiors and in the grain boundary (GB) regions in the as-prepared and HPT-deformed specimens. Our results show that most of the GBs contain lattice dislocations with high densities. The average dislocation densities determined by HRTEM and MD simulation are in good correlation with the values provided by X-ray line profile analysis. Strain distribution determined by MD simulation is shown to follow the Krivoglaz–Wilkens strain function of dislocations. Experiments, MD simulations, and theoretical analysis all prove that the sources of strain broadening in X-ray diffraction of nanocrystalline materials are lattice dislocations in the GB region. The results are discussed in terms of misfit dislocations emanating in the GB regions reducing elastic strain compatibility. The results provide fundamental new insight for understanding the role of GBs in plastic deformation in both nanograin and coarse grain materials of any grain size.

Grain Growth Control in Grain Boundary Engineered Microstructures

2012 ◽  
Vol 715-716 ◽  
pp. 103-108 ◽  
Author(s):  
Valerie Randle ◽  
Mark Coleman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Stainless Steels ◽  
Growth Control ◽  
Austenitic Stainless Steels ◽  
Grain Boundary Engineering ◽  
Size Measurement ◽  
Annealing Twins ◽  
And Control ◽  
Measurement And Control

Grain boundary engineering (GBE) to promote degradation-resistant interfaces in the microstructure usually requires that the grain size remains small so that strength is not compromised. Aspects of grain size measurement and control will be reviewed and discussed for a variety of GBE materials such as copper, nickel, nickel-based alloys and austenitic stainless steels, particularly in the light of the high proportion of annealing twins that constitute the GBE microstructure.

Influence of Annealing on the Microstructure and Mechanical Properties of Electrodeposited Nanocrystalline Nickel

2011 ◽  
Vol 683 ◽  
pp. 103-112 ◽  
Author(s):  
B. Yang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Boundary State ◽  
Microstructure And Mechanical Properties ◽  
Grain Boundary Structure ◽  
Average Grain Size ◽  
Different Grain Size

The evolution of the microstructure and mechanical properties of electrodeposited nanocrystalline Ni with different annealing procedures was studied systematically. For the annealed specimens hardness decreases with increasing average grain size but the dependence changes at different grain size ranges. The specimens annealed at a low temperature show higher hardness compared to the as-deposited nanocrystalline Ni, despite an increased measured average grain size. In association with this hardening an increase in elastic modulus and a decrease in microstrain was observed after annealing. With increasing annealing temperature both the tensile strength and the fracture strain were observed to decrease, this is companied with a transition from ductile to brittle in the fracture surfaces. These results indicated that the mechanical behaviour of nanocrystalline Ni depends not only on the average grain size but also on the grain boundary structure. A change in the grain boundary state arising from annealing may be responsible for the observed increase in hardness and elastic modulus as well as the deterioration of tensile properties.

Characterization of Zinalco Alloy Superplastically Deformed Using Orientation Imaging Microscopy

2009 ◽  
Vol 1242 ◽  
Author(s):  
Ramos A. Mitsuo ◽  
Martínez F. Elizabeth ◽  
Negrete S. Jesús ◽  
Torres-Villaseñor G.
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Orientation Imaging Microscopy ◽  
Grain Boundary Sliding ◽  
Boundary Misorientation ◽  
Average Grain Size ◽  
Grain Boundary Misorientation ◽  
Misorientation Angles

ABSTRACTZinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (ε) of 1×10-3 s-1 at homologous temperature (TH) of 0.68 (5 ). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15° and 55° was found. For deformed specimen, the fraction of angles between 15° and 55° was decreced to average value of 75% and fractions of low angle (<5°) and high angle (>55°) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15° and 55° observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation.

Effect of Grain Size on Microstructure and Aging Behavior in AM60 Magnesium Alloy

2011 ◽  
Vol 409 ◽  
pp. 373-378
Author(s):  
H. Takano ◽  
Mitsuaki Furui ◽  
Susumu Ikeno ◽  
Tomoyasu Yamaguchi ◽  
Seiji Saikawa
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Grain Boundary ◽  
Eutectic Reaction ◽  
Age Hardening ◽  
Peak Hardness ◽  
Aging Behavior ◽  
Continuous Precipitation ◽  
Hardening Behavior ◽  
Average Grain Size

Our recent studies showed that continuous and cellular precipitates are covered with the whole of crystal grain in age hardable AM60 magnesium alloy cast into permanent molds, which have the average grain size of 75-85μm. Also, continuous precipitation is generated nearby grain boundary in the same alloys cast into sand molds, which have the average grain size of 138-147μm. It’s thought that permanent mold castings have the age hardening behavior of intragranular precipitation participation type that is influenced by continuous precipitates. It’s also thought that sand mold castings have the age hardening behavior of grain boundary participation type that is influenced by cellular precipitates. In this study, AM60 magnesium alloy with larger grain size was used to detect the grain size dependence of microstructure and aging behavior. In the microstructure of as-cast condition, the larger the grain size, it was shown that the none-equilibrium crystallized β phase with eutectic reaction during the solidification between liquidus and solidus temperatures becomes large-size. In the age hardening curves, the peak hardness values become higher with decreasing of grain size.

Electrical properties of ultrafine-grained yttria-stabilized zirconia ceramics

1997 ◽  
Vol 12 (9) ◽  
pp. 2374-2380 ◽  
Author(s):  
Shusheng Jiang ◽  
Walter A. Schulze ◽  
Vasantha R. W. Amarakoon ◽  
Gregory C. Stangle
Keyword(s):  
Grain Size ◽  
Oxygen Vacancy ◽  
Grain Boundary ◽  
Oxygen Vacancies ◽  
Synthesis Process ◽  
Physical Parameters ◽  
Fine Grained ◽  
Oxygen Ion ◽  
Average Grain Size ◽  
Vacancy Concentrations

Nanoparticles of yttria-doped tetragonal zirconia polycrystalline ceramics (Y-TZP) with an average crystallite size of less than 9 nm were prepared by a combustion synthesis process. Dense and fine-grained (<200 nm) Y-TZP ceramics were obtained by fast-firing using temperatures lower than 1400 °C and dwell times of less than 2 min. Impedance spectroscopy was employed to measure conductivities of oxygen vacancies in the grain and the grain boundary of the fine-grained Y-TZP. The relationships between the concentration of the oxygen vacancies in the grain boundary and measurable physical parameters were determined semiquantitatively. The oxygen vacancy concentrations and activation energies for the oxygen-ion conduction in the grain and the grain boundary of the fine-grained Y-TZP were found to be independent of the average grain size in the average grain-size range of 90–200 nm. These experimental results suggest that, in order to retain the abnormally high oxygen vacancy concentrations of the Y-TZP nanoparticles and thus enhance the oxygen-ion conductivity, it may be necessary to decrease the average grain size to approximately 10 nm.

scholarly journals Impact of Equal Channel Angular Pressing on Mechanical Behavior and Corrosion Resistance of Hot-Rolled Ti-2Fe-0.1B Alloy

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5117
Author(s):  
Yanhuai Wang ◽  
Xin Li ◽  
I. V. Alexandrov ◽  
Li Ma ◽  
Yuecheng Dong ◽  
...  
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Titanium Alloy ◽  
Mechanical Behavior ◽  
Equal Channel Angular Pressing ◽  
Hot Rolling ◽  
Low Cost ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Hot Rolled

In the present study, the unique bimodal grain size distribution microstructure with the ultrafine substrate and embedded macro grains was fabricated by a traditional hot-rolling process in a novel low-cost Ti-2Fe-0.1B titanium alloy, which possesses a good combination of strength (around 663 MPa) and ductility (around 30%) without any post heat treatment. Meanwhile, the mechanical behavior and corrosion resistance of hot-rolled Ti-2Fe-0.1B alloy after equal channel angular pressing (ECAP) deformation were studied. Results indicated that the average grain size decreased to 0.24 μm after 4 passes ECAP deformation, which led to the enhancement of tensile strength to around 854 MPa and good ductility to around 15%. In addition, corrosion resistance was also improved after ECAP due to the rapid self-repairing and thicker passivation film. Our study revealed that the novel low-cost titanium alloy after hot-rolling and ECAP could be used instead of Ti-6Al-4V in some industrial applications due to similar mechanical behavior and better corrosion resistance.

Influence of Asymmetric Hot Rolling on Microstructures of Vessel Steel

2014 ◽  
Vol 1049-1050 ◽  
pp. 35-38
Author(s):  
Xiao Lei Bai ◽  
Zhen Guang Liu ◽  
Xiu Hua Gao ◽  
Yong Lu ◽  
Jian Ping Li
Keyword(s):  
Grain Size ◽  
Hot Rolling ◽  
Vessel Steel ◽  
Gradient Distribution ◽  
Transmission Electron ◽  
Rolled Specimen ◽  
Grain Distribution ◽  
The One ◽  
Asymmetric Hot Rolling ◽  
Electron Back Scattered Diffraction

The symmetric/asymmetric hot rolling experiments were carried out to investigate the effect of shear deformation on microstructure of vessel steel by using electron back-scattered diffraction (EBSD) and field emission transmission electron microscope. The study shows that gradient distribution grain size through the thickness is formed in asymmetric rolled specimen. The grain size in surface is smaller than the one in center. The grain distribution is homogeneous in symmetric rolled specimen. The grain in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen in the same thickness position. The precipitate particles morphology are random precipitate and interphase precipitate in symmetric and asymmetric rolled specimen. The precipitate particles tend to nucleate and grow in the grain in symmetric rolled specimen. The precipitate particles located in grain boundary are observed in asymmetric rolled specimen.

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