Grain Refinement and Strengthening of Aluminum Alloys: Cold Severe Plastic Deformation Model

2019 ◽  
Author(s):  
Xiao Guang Qiao ◽  
Nong Gao ◽  
Marco Starink
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Grain Refinement ◽  
Aluminium Alloys ◽  
Cold Deformation ◽  
Al Alloys ◽  
Deformation Model ◽  
Angular Pressing ◽  
Dislocation Movement ◽  
Very High

This paper presents a model which quantitatively predicts grain refinement and strength/hardness of Al alloys after very high levels of cold deformation through processes including cold rolling, equal channel angular pressing (ECAP), multiple forging (MF), accumulative rolling bonding (ARB) and embossing. The model deals with materials in which plastic deformation is exclusively due to dislocation movement, which is in good approximation the case for aluminium alloys. In the early stages of deformation, the generated dislocations are stored in grains and contribute to overall strength. With increase in strain, excess dislocations form and/or move to new cell walls/grain boundaries and grains are refined. We examine this model using both our own data as well as the data in the literature. It is shown that grain size and strength/hardness are predicted to a good accuracy.

Influence of Stacking Fault Energy on the Microstructures and Grain Refinement in the Cu-Al Alloys during Equal-Channel Angular Pressing

2010 ◽  
Vol 667-669 ◽  
pp. 379-384 ◽  
Author(s):  
X.H. An ◽  
Shi Ding Wu ◽  
Z.F. Zhang
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
Al Alloys ◽  
Stacking Fault ◽  
High Recovery ◽  
Angular Pressing ◽  
High Recovery Rate ◽  
Refinement Mechanism ◽  
Stacking Fault Energies

The microstructural evolution and grain refinement of Cu-Al alloys with different stacking fault energies (SFEs) processed by equal-channel angular pressing (ECAP) were investigated. The grain refinement mechanism was gradually transformed from dislocation subdivision to twin fragmentation with tailoring the SFE of Cu-Al alloys. Concurrent with the transition of grain refinement mechanism, the grain size can be refined into from ultrafine region (1 m~100 nm) to the nanoscale (<100 nm) and then it is found that the minimum equilibrium grain size decreases in a roughly linear way with lowering the SFE. Moreover, in combination with the previous results, it is proposed that the formation of a uniform ultrafine microstructure can be formed more readily in the materials with high SFE due to their high recovery rate of dislocations and in the materials with low SFE due to the easy formation of a homogeneously-twinned microstructure.

Severe Plastic Deformation under High Pressure for Production of Superplastic Materials

2016 ◽  
Vol 838-839 ◽  
pp. 287-293 ◽  
Author(s):  
Zenji Horita
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
High Pressure Torsion ◽  
High Strength ◽  
Al Alloys ◽  
Strain Rates ◽  
Ti Alloys

Grain refinement is an important prerequisite for advent of superplasticity. In particular, as the grain size is smaller, the superplasticity appears at higher strain rates and lower temperatures. Severe plastic deformation (SPD) is a useful process for achieving significant grain refinement. This presentation shows that applicability of the SPD process is enhanced when it is operated under high pressure through high-pressure torsion (HPT) and high-pressure sliding (HPS). It is demonstrated that commercially available conventional alloys but less ductile alloys such as Mg alloys, age-hardenable high-strength Al alloys (A2024, A7075) and Ti alloys become superplastic after processing by HPT or HPS.

scholarly journals Development of New Oxide Based Master Alloys and their Grain Refinement Potency in Aluminium Alloys

2015 ◽  
Vol 828-829 ◽  
pp. 23-28 ◽  
Author(s):  
Vadakke Madam Sreekumar ◽  
N. Hari Babu ◽  
Dmitry G. Eskin ◽  
Z. Fan
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Master Alloy ◽  
Aluminium Alloys ◽  
Al Alloys ◽  
Ultrasonic Cavitation ◽  
Size Reduction ◽  
Refinement Efficiency ◽  
Master Alloys

In this study, grain refinement efficiency of a new oxide master alloy based on MgAl2O4 was demonstrated in Al alloys. The grain size of the reference alloy was reduced by 50-60% with the addition of the master alloy and introduction of ultrasonic cavitation. While cooling rate has an influence on the grain size reduction, higher levels of addition of master alloy was found to be not effective in further reducing the grain size.

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

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.

scholarly journals Investigation on the Microstructure of ECAP-Processed Iron-Aluminium Alloys

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 219
Author(s):  
Bernd-Arno Behrens ◽  
Kai Brunotte ◽  
Tom Petersen ◽  
Roman Relge
Keyword(s):  
Grain Refinement ◽  
Aluminium Alloys ◽  
Aluminium Content ◽  
Microstructure Development ◽  
Chamber Furnace ◽  
Fine Grained ◽  
Angular Pressing ◽  
Ecap Process ◽  
Average Grain Size ◽  
Forming Temperature

The present work deals with adjusting a fine-grained microstructure in iron-rich iron-aluminium alloys using the ECAP-process (Equal Channel Angular Pressing). Due to the limited formability of Fe-Al alloys with increased aluminium content, high forming temperatures and low forming speeds are required. Therefore, tool temperatures above 1100 °C are permanently needed to prevent cooling of the work pieces, which makes the design of the ECAP-process challenging. For the investigation, the Fe-Al work pieces were heated to the respective hot forming temperature in a chamber furnace and then formed in the ECAP tool at a constant punch speed of 5 mm/s. Besides the chemical composition (Fe9Al, Fe28Al and Fe38Al (at.%—Al)), the influences of a subsequent heat treatment and the holding time on the microstructure development were investigated. For this purpose, the average grain size of the microstructure was measured using the AGI (Average Grain Intercept) method and correlated with the aforementioned parameters. The results show that no significant grain refinement could be achieved with the parameters used, which is largely due to the high forming temperature significantly promoting grain growth. The holding times in the examined area do not have any influence on the grain refinement.

Role of Strain Gradient and Dynamic Transformation on the Formation of Nanocrystalline Structure Produced by Severe Plastic Deformation

2007 ◽  
Vol 539-543 ◽  
pp. 2787-2792 ◽  
Author(s):  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Jin Guo Li ◽  
Koichi Tsuchiya
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Strain Gradient ◽  
High Pressure Torsion ◽  
Large Strain ◽  
Nanocrystalline Structure ◽  
Angular Pressing ◽  
Dynamic Transformation ◽  
Fine Grained Structure

Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain size larger than 100 nm) had been obtained in many processes such as heavy cold rolling, equal channel angular pressing (ECAP) or accumulative roll bonding (ARB), the formation of nano grained structure (< 100 nm) is limited to processes such as ball milling, shot peening or drilling. In the present study, high pressure torsion (HPT) deformation and drilling were carried out to understand the conditions necessary to obtain nano grained structure in steels. The results of HPT experiments in pure Fe showed that HPT has superior ability of strengthening and grain refinement probably due to a strain gradient but the saturation of grain refinement occurs before reaching nano grained structure. Drilling experiments in high carbon martensitic steel revelaed that nano grained ferrite forms at the drilled hole surface only when the transformation from ferrite to austenite takes place during drilling. Considering various other processes by which nano grained ferrite was produced, it is proposed that heavy strains with large strain gradients together with dynamic transformation are necessary to reach nano grained ferrite structure.

Severe Plastic Deformation of Al-15Zn-2Mg Alloy: Effect on Wear Properties

2019 ◽  
Vol 803 ◽  
pp. 22-26
Author(s):  
G.K. Manjunath ◽  
K. Udaya Bhat ◽  
G.V. Preetham Kumar
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Wear Test ◽  
Zinc Content ◽  
Wear Properties ◽  
Significant Drop ◽  
Angular Pressing ◽  
First Pass ◽  
Alloy Effect

In the present work, Al-Zn-Mg alloy having highest zinc content was deformed by one of the severe plastic deformation (SPD) technique, equal channel angular pressing (ECAP) and effect of ECAP on the microstructure evolution and the wear properties were studied. ECAP was performed in a split die and the channels of the die are intersecting at an angle of 120º. ECAP was attempted at least possible temperature and the alloy was successfully ECAPed at 423 K. Below this temperature samples were failed in the first pass itself. After ECAP, significant drop in the grain size was reported. Also, ECAP leads to significant raise in the microhardness of the alloy. Predominantly, after ECAP, upsurge in the wear resistance of the alloy was noticed. To figure out the response of ECAP on the wear properties of the alloy; worn surfaces of the wear test samples were analyzed in SEM.

scholarly journals Research of structural entropy of sheet aluminium alloys depending on annealing temperature

2018 ◽  
Vol 224 ◽  
pp. 03005
Author(s):  
Ekaterina Nosova ◽  
Fedor Grechnikov ◽  
Natalia Lukonina
Keyword(s):  
Grain Size ◽  
Aluminium Alloys ◽  
Annealing Temperature ◽  
Cold Deformation ◽  
Grain Structure ◽  
Sheet Stamping ◽  
Structural Entropy ◽  
Size Uniformity

Sheet blanks’ structure uniformity determines their ability to sheet stamping. Level of entropy may represent the characteristic of structural uniformity. Structural entropy was received from strain curves recalculation for sheet blanks from aluminium alloys Al-2Mg and Al-6Mg are presented in the work. Stain curves were provided for blanks after cold deformation and annealing at temperatures 250, 350 И 450˚C. Estimation of grain size uniformity was made. Effect of annealing temperature on structural entropy and grain structure uniformity was found. It was shown that annealing temperature increasing leads to structural entropy decreasing. Ununiformity of grain size achieves the minimal values after annealing at temperature 350˚C for both alloys, and then ununiformity grows after annealing at temperature 450˚C.

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