Hall-Petch Relationship in an Al-Mg-Sc Alloy Subjected to ECAP

2014 ◽  
Vol 922 ◽  
pp. 120-125 ◽  
Author(s):  
Andrii Dubyna ◽  
Anna Mogucheva ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Refinement ◽  
Volume Fraction ◽  
Strain Range ◽  
High Strength ◽  
Strengthening Mechanisms ◽  
Dispersion Strengthening ◽  
Remarkable Effect ◽  
Petch Relationship ◽  
Angular Pressing ◽  
Average Size

Effect of extensive grain refinement on mechanical properties of an Al-Mg-Sc alloy subjected to equal-channel angular pressing (ECAP) at 300°C is considered in detail. It was shown that the Hall-Petch relationship with the coefficient, ky, of 0.2 MPa×m1/2 is valid in a wide strain range despite a great difference in deformation structures. Volume fraction of fine grains with an average size of ∼1 μm gradually increases with strain. It is caused by the fact that additive contributions of grain size strengthening and dislocation strengthening to the overall strengthening take place in this alloy. Upon ECAP the extensive grain refinement is accompanied by increasing dislocation density. Superposition of deformation and structural strengthening mechanisms provides achieving very high strength in the alloy. It was shown that ECAP at 300°C has no remarkable effect on a dispersion of coherent dispersoids. Al3(Sc,Zr), which gives a significant contribution to overall strength through dispersion strengthening. Contributions of different strengthening mechanisms to overall strength of the material are analyzed.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

scholarly journals Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

Strengthening Mechanisms and Tribological Properties of Ultra-Hard AlMgB14 Based Composite Reinforced with TiB2

2020 ◽  
Vol 12 (6) ◽  
pp. 866-872
Author(s):  
Wen Liu ◽  
Chun-Yan Hao ◽  
Xu-Dong Zhao ◽  
Xiang-Jun Wang ◽  
Guo-Liang Shi
Keyword(s):  
Fracture Toughness ◽  
Friction And Wear ◽  
Room Temperature ◽  
High Strength ◽  
Strengthening Mechanisms ◽  
Interface Bonding ◽  
Dispersion Strengthening ◽  
Hard Phase ◽  
Phase Dispersion ◽  
Relative Hardness

AlMgB14–TiB2 composites with ideal structures are successfully prepared by field activated and pressure assisted synthesis. The effects of different TiB2 contents on the relative hardness and toughness of the composites were investigated. The results showed adding TiB2 could both increase the hardness of AlMgB14 and improve the fracture toughness. The TiB2 contributed more to the hardness than to the toughness. The microstructure analysis shows that the main toughening mechanisms of AlMgB14–TiB2 composites are hard phase dispersion strengthening, high-strength interface bonding and the high elastic modulus of TiB2. Therefore, reducing the particle size of TiB2 to nanoscale is an efficient way to improve the toughness and hardness. The results of friction and wear experiment at room temperature have shown that the addition of TiB2 into AlMgB14 enhances the abrasion–resistant property.

scholarly journals The Effect of Equal-Channel Angular Pressing on Microstructure, Mechanical Properties, and Biodegradation Behavior of Magnesium Alloyed with Silver and Gadolinium

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 918
Author(s):  
Boris Straumal ◽  
Natalia Martynenko ◽  
Diana Temralieva ◽  
Vladimir Serebryany ◽  
Natalia Tabachkova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
Fine Particles ◽  
Volume Fraction ◽  
Galvanic Corrosion ◽  
Angular Pressing ◽  
Average Grain Size ◽  
The Matrix ◽  
Mechanical Properties And Corrosion

The effect of equal channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, and corrosion resistance of the alloys Mg-6.0%Ag and Mg-10.0%Gd was studied. It was shown that ECAP leads to grain refinement of the alloys down to the average grain size of 2–3 μm and 1–2 μm, respectively. In addition, in both alloys the precipitation of fine particles of phases Mg54Ag17 and Mg5Gd with sizes of ~500–600 and ~400–500 nm and a volume fraction of ~9% and ~8.6%, respectively, was observed. In the case of the alloy Mg-6.0%Ag, despite a significant grain refinement, a drop in the strength characteristics and a nearly twofold increase in ductility (up to ~30%) was found. This behavior is associated with the formation of a sharp inclined basal texture. For alloy Mg-10.0%Gd, both ductility and strength were enhanced, which can be associated with the combined effect of significant grain refinement and an increased probability of prismatic and basal glide. ECAP was also shown to cause a substantial rise of the biodegradation rate of both alloys and an increase in pitting corrosion. The latter effect is attributed to an increase in the dislocation density induced by ECAP and the occurrence of micro-galvanic corrosion at the matrix/particle interfaces.

Equal Channel Angular Pressing of Al Alloy AA2219

2009 ◽  
Vol 67 ◽  
pp. 53-58
Author(s):  
V. Anil Kumar ◽  
M.K. Karthikeyan ◽  
Rohit Kumar Gupta ◽  
P. Ramkumar ◽  
P.P. Sinha
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
High Strength ◽  
Dark Field ◽  
Grain Structure ◽  
Al Alloy ◽  
Angular Pressing

Severe plastic deformation processes (SPD) are gaining importance as advanced materials processing techniques and hold immense potential in obtaining ultra fine-grained high strength materials. Among the SPD techniques, Equal channel angular pressing (ECAP) has its own merits to produce materials with ultra fine grains in bulk with better mechanical properties. The material deforms with high level of plastic strain inside the channel resulting in grain refinement of the output material with improvement in mechanical properties. A very viable die configuration was conceptualized and die was made with 1200 channel angle. Processing of 25 mm dia. of Al alloy AA2219 at room temperature was successfully carried out and grain refinement was observed. The mechanism of grain refinement has been studied using optical and transmission electron microscopy (TEM). It was observed that low energy dislocation structure (LEDS) forms concurrently with sub-grain structure due to dislocation rearrangements, which provide stability to the evolving sub-grain structure. Dislocation mobility is hindered by the presence of precipitates and / or intermetallic dispersoids present in the matrix and results in presence of dislocations in grain interiors. The pile up of dislocations at intermetallic dispersoids was confirmed from the dark field TEM micrographs. Present paper describes the experimental procedure and followed to attain severe plastic deformation through ECAP. Increase in hardness as well as refinement in the grain size after 5-passes have been discussed in light of extensive optical and TEM. The mechanisms of grain refinement to achieve nano-grained structure and strengthening accrued from the grain refinement through ECAP has been discussed.

Fracture Analysis and Mechanical Properties of Magnesium Based Composites

2017 ◽  
Vol 891 ◽  
pp. 526-532 ◽  
Author(s):  
Beáta Ballóková ◽  
Dagmar Jakubéczyová
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Tensile Tests ◽  
Fracture Analysis ◽  
Physical Parameters ◽  
Weight Percentage ◽  
Matrix Microstructure ◽  
Angular Pressing ◽  
The Matrix ◽  
Average Size

Mechanical properties and microstructure and fracture analysis of a magnesium alloys based composite series with different volume fraction of alumina dispersoid nanoparticles were studied. The initial states of the composites were further treated by severe plastic deformation (SPD) using equal channel angular pressing (ECAP) in order to achieve microstructures with very fine grains of matrix. Microstructure parameters, in particular the matrix grain size, average size of the dispersed particles and their distribution, were observed using optical microscopy. The average grain sizes of MMCs decreased evidently with the increase of the weight percentage of Al2O3 particles additions and ECAP passes. The heat deformation process of such materials, besides the formation of incorporated Al2O3 particles, also leads to the creation of intermetallic compound Mg17Al12. Fracture surfaces after tensile tests at room and elevated temperature were studied by SEM. The fracture of studying materials were characterized as the ductile fracture due to the existence of a large number of dimples.In summary, it has been shown that mechanical properties are affected by lattice, physical parameters of phases within the composite systems. They are also affected by microstructure and substructure, which depend on the technology of compaction and densification.

Strategy for Achieving High Strength in Al-Mg-Sc Alloys by Intense Plastic Straining

2012 ◽  
Vol 706-709 ◽  
pp. 55-60 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Anna Mogucheva ◽  
Andrii Dubyna
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
High Strength ◽  
Necessary Condition ◽  
Angular Pressing ◽  
Strength Increment ◽  
Hardened Condition

It is shown that implementation of high strains through equal-channel angular pressing (ECAP) and/or rolling into alloys belonging to Al-Mg-Sc-Zr system allows achieving high strength and satisfactory ductility. It was shown that strain hardening gives a main contribution to overall strength increment attributed to intense plastic straining; the role of grain size hardening is minor. However, extensive grain refinement is a necessary condition for retaining sufficient ductility in full-hardened condition for these materials.

Grain Refinement by High Temperature Plane-Strain Compression of Fe-2%Si Steel

2006 ◽  
Vol 503-504 ◽  
pp. 977-982
Author(s):  
Pablo Rodriguez-Calvillo ◽  
Ana Carmen C. Reis ◽  
Leo Kestens ◽  
Yvan Houbaert
Keyword(s):  
Plane Strain ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Orientation Imaging Microscopy ◽  
Plane Strain Compression ◽  
Initial Structure ◽  
Deformation Bands ◽  
Engineering Strain ◽  
Post Process ◽  
Average Size

An Fe-2%Si alloy, which was designed for electromagnetic applications was submitted to a series of plane strain compression (PSC) tests with reductions of 25, 35 and 75% at temperatures varying from 800 to 1,100°C and at a constant engineering strain rate corresponding to a constant cross velocity of 20 mm/s. The initial structure of the material displayed nearly equi-axed grains with an average size of 80 μm. The as-received texture was characterised by a nearly random cube fibre (<100>//ND) with a relatively weak maximum on the rotated cube component ({001}<110>). After deformation the samples were water quenched in order to avoid post-process static recrystallization events. The microstructures were analysed by orientation imaging microscopy (OIM) revealing that the zone of PSC was restricted to the central layers of the sample but minimally covering 50% of the sample thickness. After deformation at 800°C the conventional lamellar deformation structures were observed on the sections perpendicular to the transverse direction of PSC. At higher deformation temperatures the structure was of a bimodal nature consisting of lamellar deformation bands and equi-axed small grains. The volume fraction of these small equi-axed grains increased from 19.9% after 75%reduction at 800°C to 67.8% after 75% reduction at 1.100°C. After 75% reduction the equi-axed grains exhibited an average size of 10 μm which represents a strong grain refinement with respect to the initial size of 80 μm prior to PSC. Ferrite Silicon steels undergo extensive dynamic recovery during hot working. Dynamic recrystallization (DRX), though, has not yet been reported for these alloys although the present data suggest that a DRX mechanism might be responsible for the remarkable grain refinement after relatively low amounts of strain applied at high temperatures.

Microstructure and Mechanical Properties of High Strength Al2O3p/6061Al Composites

2007 ◽  
Vol 353-358 ◽  
pp. 1390-1393
Author(s):  
Bai Feng Luan ◽  
Gao Hui Wu ◽  
Qing Liu ◽  
Niels Hansen ◽  
Ting Quan Lei
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Hot Extrusion ◽  
High Strength ◽  
Dispersion Strengthening ◽  
Particle Volume ◽  
Microstructure And Mechanical Properties ◽  
Before And After

An experimental study of microstructure and mechanical properties in the Al2O3 particulate reinforced 6061 Aluminum composites has been used to determine the effect of extrusion and particle volume fraction (20, 26, 30, 40, 50, 60%Vf) in deformed metal matrix composites. The microstructure of Al2O3 /6061Al composite before and after hot extrusion is investigated by TEM and SEM. Results show that dislocation and subgrain generated after hot extrusion as well as the particle distribution of composite become more uniform with extrusion ratio of 10:1. The ultimate strength, yield strength and elongation of the composite also increase after hot extrusion. Dispersion strengthening and subgrain boundary strengthening is discussed and also the effect of precipitate introduced by heat treatment both after casting and after extrusion. The yield stress (0.2% offset) of the composites has been calculated and predicted using a standard dislocation hardening model. Whilst the correlation between this and the measured value of yield stress obtained in previous experimental test is reasonable.

Strengthening Mechanisms of Vanadium Micro-Alloyed Reinforcing Steel Bar

2011 ◽  
Vol 130-134 ◽  
pp. 942-945
Author(s):  
Lie Jun Li ◽  
Xiang Dong Huo ◽  
Lin Guo
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Precipitation Hardening ◽  
High Strength ◽  
Experimental Methods ◽  
Strengthening Mechanisms ◽  
Large Numbers ◽  
Steel Bar ◽  
Micro Alloyed Steel ◽  
Grain Refinement Strengthening

High strength vanadium micro-alloyed steel with yield strength of 600MPa has been developed based on commercial 20MnSi steel bar. Experimental methods, such as OM, SEM and TEM, were used to study the experimental steels. Compared with 20MnSi, steel 20MnSiV boasts much finer microstructure, and large numbers of nanometer precipitates exist in the specimens of 20MnSiV. Analysis shows that strength of 20MnSiV dramatically increases through grain refinement strengthening and precipitation hardening of nanometer VCN particles.

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