scholarly journals Thermal Stability and Mechanical Properties of Al-Zn and Al-Bi-Zn Alloys Deformed by ECAP

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2043
Author(s):  
Hailong Jia ◽  
Yinan Piao ◽  
Kaining Zhu ◽  
Chaoran Yin ◽  
Wenqiang Zhou ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Thermally Induced ◽  
Ultrafine Grains ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Ultrafine Grain Structure

It is well known that ultrafine grained and nanocrystalline materials show enhanced strength, while they are susceptible to thermally induced grain coarsening. The present work aims to enhance the thermal stability of ultrafine Al grains produced by equal channel angular pressing (ECAP) via dynamically precipitation. Detailed characterization by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) has been carried out to reveal the microstructural evolution during both ECAP and post-ECAP annealing. After five passes of ECAP, both Al-8Zn and Al-6Bi-8Zn alloys show an ultrafine grain structure together with dynamic precipitated nanoscale Zn particles along grain boundaries. Upon annealing at 200 °C, ultrafine grains in the Al-8Zn and Al-6Bi-8Zn alloys show a remarkable thermal stability compared to the Al-8Bi alloy, which is mainly due to the presence of nanoscale Zn precipitates along grain boundaries. The present work reveals that nanoscale Zn particles have a positive effect on preserving the ultrafine grains during annealing, which is useful for the design of UFG Al alloys with improved thermal stability.

Grain Refinement of an Al-Cu-Mg Alloy by Microalloying and Common Thermo-Mechanical Treatment

2007 ◽  
Vol 546-549 ◽  
pp. 917-922
Author(s):  
Bao Lin Wu ◽  
Gui Ying Sha ◽  
Yi Nong Wang ◽  
Yu Dong Zhang ◽  
Claude Esling
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Mechanical Treatment ◽  
Grain Structure ◽  
Mg Alloy ◽  
Ultrafine Grain ◽  
Fine Grain ◽  
Thermo Mechanical Treatment ◽  
Ultrafine Grain Structure ◽  
Thermal Stability Of

Heavy deformation plus micro alloying could be an effective way to obtain ultrafine grain structure of metals. In the present work, an Al-Cu-Mg alloy was microalloyed with Zr to obtain homogeneous precipitates and then heavily deformed by conventional forging at high temperature. The possible refining processing routes were studied and the superplasticity behaviors of the alloy was investigated. Results show that the micro alloyed alloy can be stably refined to 3-5μm under conventional processing routes. The Al-3Zr precipitates act both as additional sites to enhance recrystallization nucleation rate and pins to impede grain growth to increase the thermal stability of the fine grain structure. However, as the Al3Zr precipitates remains along grain boundaries, the superplastic capability of the material is not high. At 430°C with 1×10-4S-1 strain rate, the elongation obtained was 260%.

Microstructural Evolution and Grain Refinement in a Cu-Zr Alloy Processed by High-Pressure Torsion

2014 ◽  
Vol 783-786 ◽  
pp. 2635-2640 ◽  
Author(s):  
Jittraporn Wongsa-Ngam ◽  
Terence G. Langdon
Keyword(s):  
High Pressure ◽  
Grain Refinement ◽  
Microstructural Evolution ◽  
High Pressure Torsion ◽  
Electron Backscatter Diffraction ◽  
Grain Morphology ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Refinement Mechanism ◽  
Ultrafine Grain Structure

A copper alloy, Cu-0.1% Zr, was processed at room temperature by high-pressure torsion (HPT) in order to evaluate the microstructural evolution and grain refinement mechanism. Transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques were employed to measure the grain morphology, grain size distributions and the distribution of the misorientation angles. The results demonstrate that this processing procedure has a potential for producing an ultrafine-grain structure containing reasonably equiaxed grain with high-angle boundary misorientations. The grain refinement mechanism is primarily governed by dislocation activities.

Nature of Formation of the Areas Having an Ultrafine Grain Structure in Al-Li-Mg System Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 265-270
Author(s):  
A.A. Alekseev ◽  
O.A. Setjukov ◽  
E.A. Lukina ◽  
I.N. Fridlyander
Keyword(s):  
Optical Metallography ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
System Alloy ◽  
Complex Phase ◽  
X Ray ◽  
Transmission Electron ◽  
Ultrafine Grain Structure ◽  
Composition Changes ◽  
Complex Phase Composition

The structure of Al-Li-Mg system alloy 1420, containing a small quantity of Sc, Zr, Ti was investigated in cast, homogenized, hot-pressed, quenched and aged conditions, using the methods of optical metallography, transmission electron microscopy and X-ray examination. An existence of areas, having fine grains (20-30 nm)- "Ultrafine Grain areas"(UFGA) was observed in all the investigated conditions. UFGA are located on the boundaries, sub boundaries and S1(Al2MgLi) phase particles. UFGA can also form near the particles of crystallization origin. These areas have a complex phase composition. Inside the UFGA the particles of S1(Al2MgLi) phase and also δnon-phase, investigated in [1] are always present whereas δ'(Al3Li) precipitations are absent. These areas are formed during crystallization and hot deformation. Their composition changes during the treatment. The nature of these changes is considered.

Characterization of Ultrafine Grain Structure in 5083 Al Alloy Made by Equal Channel Angular Pressing

2004 ◽  
Vol 10 (S02) ◽  
pp. 564-565
Author(s):  
Yong Jun Oh ◽  
Yong Shin Kim ◽  
Kyung Tae Park ◽  
Kyu Hwan Oh ◽  
Dong Hyuk Shin
Keyword(s):  
Equal Channel Angular Pressing ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Al Alloy ◽  
Angular Pressing ◽  
Ultrafine Grain Structure ◽  
5083 Al Alloy

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

scholarly journals Evading strength-corrosion tradeoff in Mg alloys via dense ultrafine twins

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Changjian Yan ◽  
Yunchang Xin ◽  
Xiao-Bo Chen ◽  
Daokui Xu ◽  
Paul K. Chu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundaries ◽  
Galvanic Corrosion ◽  
High Strength ◽  
Mg Alloys ◽  
Grain Structure ◽  
Localized Corrosion ◽  
Ultrafine Grain ◽  
Ultrafine Grain Structure ◽  
Non Equilibrium

AbstractConventional ultrafine-grains can generate high strength in Mg alloys, but significant tradeoff of corrosion resistance due to inclusion of a large number of non-equilibrium grain boundaries. Herein, an ultrafine-grain structure consisting of dense ultrafine twins is prepared, yielding a high strength up to 469 MPa and decreasing the corrosion rate by one order of magnitude. Generally, the formation of dense ultrafine twins in Mg alloys is rather difficult, but a carefully designed multi-directional compression treatment effectively stimulates twinning nucleation within twins and refines grain size down to 300 nm after 12-passes compressions. Grain-refinement by low-energy twins not only circumvents the detrimental effects of non-equilibrium grain boundaries on corrosion resistance, but also alters both the morphology and distribution of precipitates. Consequently, micro-galvanic corrosion tendency decreases, and severe localized corrosion is suppressed completely. This technique has a high commercial viability as it can be readily implemented in industrial production.

Al-5Cu Alloy Processed by Equal-Channel Angular Pressing

2016 ◽  
Vol 879 ◽  
pp. 843-848 ◽  
Author(s):  
Hai Long Jia ◽  
Knut Marthinsen ◽  
Yan Jun Li
Keyword(s):  
Equal Channel Angular Pressing ◽  
Electron Backscatter Diffraction ◽  
Uniform Elongation ◽  
Rate Sensitivity ◽  
High Strength ◽  
Secondary Phase ◽  
Grain Structure ◽  
Ultrafine Grains ◽  
Cu Content ◽  
Angular Pressing

An ECAP (equal channel angular pressing) processed UFG Al-5Cu alloy was characterized by electron backscatter diffraction (EBSD). It is revealed that a bimodal grain structure, i.e. ultrafine grains accompanied by micron-sized grains was developed after 4 passes. A high strength (~501 MPa) and a relatively large elongation to failure (~28%) with ~5% uniform elongation were achieved simultaneously after 4 passes of ECAP. The high strength is due to a combination of strengthening by solute, high density of dislocations and ultrafine grains. The enhancement of uniform elongation is primarily due to the enhanced work hardening resulted from the solute Cu content and the bimodal grain structure. The large post-uniform elongation is attributed to the high strain rate sensitivity of the UFG Al-5Cu alloy. More importantly, the present work revealed that during ECAP high solid solution content of Cu and coarse secondary phase particles can introduce inhomogeneous deformation resulting in a desirable bimodal grain structure, which can be utilized as a strategy to gain both high strength and relatively good ductility.

Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

2008 ◽  
Vol 584-586 ◽  
pp. 182-187
Author(s):  
Lilia Kurmanaeva ◽  
Yulia Ivanisenko ◽  
J. Markmann ◽  
Ruslan Valiev ◽  
Hans Jorg Fecht
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Materials Science ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Ultrafine Grained ◽  
Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

Ultrafine Grain Structure Development in Aluminium Alloy by Strain Hardening using CCGP

2021 ◽  
Vol 1 (2) ◽  
pp. 25-31
Author(s):  
HS Siddesha ◽  
Suhaaskapardhi BS ◽  
Goutham C
Keyword(s):  
Tensile Strength ◽  
Aluminium Alloy ◽  
Research Work ◽  
Industrial Applications ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Fine Grained ◽  
Processed Material ◽  
Super Plastic ◽  
Ultrafine Grain Structure

Severe Plastic Deformation (SPD) processes are for developing ultrafine grained (UFG) structured materials for different Industrial applications. Cyclic Constrained Groove Pressing (CCGP) is a technique, produce fine grained structures in metallic sheets or plates in mass production. The objective of research work is to investigate the influence of CCGP processing on the super plastic behaviour of an Aluminium alloy. Samples in “ascast” materials processed by CCGP with as cast, 1, 2, 3 and 4 passes. Processed Material study for microhardness and Tensile strength mechanical properties test were done for different test specimens. Grain refinement, microhardness and Tensile strength increased with the number of CCGP passes.

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