The Influence of Work Hardening, Internal Stresses, and Stress Relaxation on Ductility of Ultrafine Grained Materials Prepared by Severe Plastic Deformation

2009 ◽  
Vol 633-634 ◽  
pp. 263-272
Author(s):  
David G. Morris ◽  
Maria A. Muñoz-Morris ◽  
Ivan Gutierrez-Urrutia
Keyword(s):  
Plastic Deformation ◽  
Stress Relaxation ◽  
Severe Plastic Deformation ◽  
Work Hardening ◽  
Deformation Behaviour ◽  
High Strength ◽  
Internal Stresses ◽  
Fracture Ductility ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Ultrafine grained materials prepared by methods of severe plastic deformation appear to show good ductility for their high strength. To a large extent this ductility enhancement, for the given strength, is shown to correspond to the fracture ductility and not the uniform ductility at maximum stress. The improved fracture ductility is often due to the refinement or removal of the coarse defects that act as sites for failure nucleation. The low work hardening rate inherent to the very fine microstructures produced by severe plastic deformation essentially condemns such materials to very low uniform ductility. Stress relaxation occurring during unloading after processing, and changes of internal stresses during reloading for mechanical testing, appear to play a significant role in determining deformation behaviour near the onset of plastic flow, and this can affect the measured uniform strain.

The New SPD Processing Trends to Fabricate Bulk Nanostructured Materials

2006 ◽  
Vol 114 ◽  
pp. 7-18 ◽  
Author(s):  
Ruslan Valiev
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Nanostructured Materials ◽  
Nanocrystalline Materials ◽  
Commercial Production ◽  
Materials Processing ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Bulk Nanocrystalline

During the last decade severe plastic deformation (SPD) has become a widely known method of materials processing used for fabrication of ultrafine-grained materials with attractive properties. Nowadays SPD processing is rapidly developing and is on the verge of a transition from lab-scale research to commercial production. This paper focuses on several new trends in the development of SPD techniques for effective grain refinement, including those for commercial alloys and presents new SPD processing routes to produce bulk nanocrystalline materials.

scholarly journals On the origin of the extremely high strength of ultrafine-grained Al alloys produced by severe plastic deformation

2010 ◽  
Vol 63 (9) ◽  
pp. 949-952 ◽  
Author(s):  
R.Z. Valiev ◽  
N.A. Enikeev ◽  
M.Yu. Murashkin ◽  
V.U. Kazykhanov ◽  
X. Sauvage
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Strength ◽  
Al Alloys ◽  
Ultrafine Grained

Prediction of the Stress-Strain Response of the Ultrafine-Grained Materials Using Multi-Scale Analysis

2010 ◽  
Author(s):  
Mihaela Banu ◽  
Mitica Afteni ◽  
Alexandru Epureanu ◽  
Valentin Tabacaru
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Aluminum Alloy ◽  
Severe Plastic Deformation ◽  
Scale Analysis ◽  
Multi Scale ◽  
Ultrafine Grained ◽  
Deformation Processes ◽  
Ultrafine Grained Materials ◽  
Multi Scale Analysis

There are several severe plastic deformation processes that transform the material from microsized grains to the nanosized grains under large deformations. The grain size of a macrostructure is generally 300 μm. Following severe plastic deformation it can be reached a grain size of 200 nm and even less up to 50 nm. These structures are called ultrafine grained materials with nanostructured organization of the grains. There are severe plastic deformation processes like equal angular channel, high pressure torsion which lead to a 200 nm grain size, respectively 100 nm grain size. Basically, these processes have a common point namely to act on the original sized material so that an extreme deformation to be produced. The severe plastic deformation processes developed until now are empirically-based and the modeling of them requires more understanding of how the materials deform. The macrostructural material models do not fit the behavior of the nanostructured materials exhibiting simultaneously high strength and ductility. The existent material laws need developments which consider multi-scale analysis. In this context, the present paper presents a laboratory method to obtain ultrafine grains of an aluminum alloy (Al-Mg) that allows the microstructure observations and furthermore the identification of the stress–strain response under loadings. The work is divided into (i) processing of the ultrafine-grained aluminum alloy using a laboratory-scale process named in-plane controlled multidirectional shearing process, (ii) crystallographic analysis of the obtained material structure, (iii) tensile testing of the ultrafine-grained aluminum specimens for obtaining the true stress-strain behavior. Thus, the microscale phenomena are explained with respect to the external loads applied to the aluminum alloy. The proposed multi-scale analysis gives an accurate prediction of the mechanical behavior of the ultrafine-grained materials that can be further applied to finite element modeling of the microforming processes.

scholarly journals Potential of High Compressive Ductility of Ultrafine Grained Copper Fabricated by Severe Plastic Deformation

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1503
Author(s):  
Mayu Asano ◽  
Motohiro Yuasa ◽  
Hiroyuki Miyamoto ◽  
Tatsuya Tanaka ◽  
Can Erdogan ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Void Formation ◽  
Rate Sensitivity ◽  
High Strength ◽  
Local Strain ◽  
Tensile Tests ◽  
Dislocation Slip ◽  
Shear Mode ◽  
Ultrafine Grained

Severe plastic deformation (SPD) can fabricate high-strength materials by forming an ultrafine grained (UFG) microstructure. Low elongation to failure of UFG materials in tensile tests, which has often been regarded as a measure of ductility of materials, has been attributed to low strain hardening of UFG structures where dislocation slip and its accumulation is very limited. In the present work, it is shown that the compressive extensibility of UFG materials can be comparable or potentially superior to that of annealed materials by using a parallel round-bar compression (PRBC) test which was designed for imposing an appropriate stress state preferable for high ductility using the shear mode. The high compressive extensibility of UFG materials can be a result of high accommodation of local strain incompatibility at non-equilibrium grain boundaries and a grain boundary-mediated deformation mechanism, which result in high damage tolerance against void formation and growth. Low strain rate sensitivity indicated that the superplastic viscous nature of deformation is not involved in the high compressive ductility of UFG materials using SPD.

THE PROPERTIES OF BULK ULTRAFINE-GRAINED METALS PROCESSED THROUGH THE APPLICATION OF SEVERE PLASTIC DEFORMATION

2012 ◽  
Vol 05 ◽  
pp. 299-306
Author(s):  
TERENCE G. LANGDON
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Elevated Temperatures ◽  
High Pressure Torsion ◽  
Superplastic Forming ◽  
High Strength ◽  
Basic Principles ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Processing Techniques

Processing through the application of severe plastic deformation (SPD) provides a very attractive tool for the production of bulk ultrafine-grained materials. These materials typically have grain sizes in the submicrometer or nanometer ranges and they exhibit high strength at ambient temperature and, if the ultrafine grains are reasonably stable at elevated temperatures, they have a potential for use in superplastic forming operations. Several procedures are now available for applying SPD to metal samples but the most promising are Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT). This paper examines the basic principles of ECAP and HPT and describes some of the properties that may be achieved using these processing techniques.

Influence of Severe Plastic Deformation on Mechanical Properties of an AA5024 Alloy

2016 ◽  
Vol 879 ◽  
pp. 1317-1322 ◽  
Author(s):  
Anna Mogucheva ◽  
Diana Yuzbekova ◽  
Tatiana Lebedkina ◽  
Mikhail Lebyodkin ◽  
Rustam Kaibyshev
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Strength ◽  
Coarse Grained ◽  
Type B ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Dislocation Strengthening

The paper reports on the effect of severe plastic deformation on mechanical properties of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (in wt. pct.) alloy processed by equal channel angular pressing followed by cold rolling (CR). The sheets of the 5024 alloy with coarse grained (CG) structure exhibited a yield stress (YS) near 410 MPa and an ultimate tensile strength (UTS) of 480 MPa, while the YS and UTS of this material with ultrafine-grained (UFG) structure increased to 530 and 560 MPa, respectively. On the other hand, the elongation to failure decreased by a factor of 2 and 4 after CR and CR following ECAP, respectively. It was shown that dislocation strengthening attributed to extensive CR plays a major role in achieving high strength of this alloy. Besides these macroscopic characteristics, jerky flow caused by the Portevin-Le Chatelier (PLC) instability of plastic deformation was examined. The formation of UFG structure results in a transition from mixed type A+B to pure type B PLC serrations. No such effect on the serrations type was observed after CR.

Developing Superplasticity in Metallic Alloys through the Application of Severe Plastic Deformation

2008 ◽  
Vol 604-605 ◽  
pp. 97-111 ◽  
Author(s):  
Roberto B. Figueiredo ◽  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Elevated Temperatures ◽  
Metallic Alloys ◽  
Superplastic Flow ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Processing through the application of severe plastic deformation (SPD) provides an opportunity for achieving very significant grain refinement in bulk metals. Since the occurrence of superplastic flow generally requires a grain size smaller than ~10 µm, it is reasonable to anticipate that materials processed by SPD will exhibit superplastic ductilities when pulled in tension at elevated temperatures. This paper summarizes the fundamental principles of SPD processing and describes recent results demonstrating the occurrence of exceptional superplastic flow in these ultrafine-grained materials.

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