Severe Plastic Deformation Technology

  • ID: 4372277
  • Book
  • 272 Pages
  • Whittles Publishing
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Provides an insight into the theory and practice of the severe plastic technology used to refine grain structure and improve properties of metallic materials. It is the only book to be entirely devoted to SPD processes/techniques and is written by a team of international experts.

In the past, improvements in the properties of metallic materials were achieved mainly by adding more alloying elements and/or applying complex thermo- mechanical treatments. The former is a costly solution and may involve rare or strategic elements while the latter is usually limited in terms of the achievable improvements.

Recently, a more unconventional approach has been tried, which is based on refining grain structure of metals below the level normally achievable by traditional techniques, that is below an average grain size of 1µm. Such metals are referred to as ultrafine grained (UFG) metals.

The most feasible method of producing UFG metals is based on so-called severe plastic deformation (SPD), a new branch of metal forming technology, in which very large plastic deformation of the material is not accompanied by any substantial change of its shape and dimensions.

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1 Equal channel angular extrusion (ECAE)
1.1 Introduction
1.2 Materials processing for properties
1.2.1 Processing mechanics
1.2.2 Structure evolution and deformation mode
1.3 SPD processes
1.4 Concept and history of ECAE
1.4.1 Concept of ECAE
1.4.2 History of ECAE
1.5 Plastic zone during ECAE
1.5.1 Frictionless conditions
1.5.2 Uniform friction in channels
1.5.3 Non-uniform friction in channels
1.5.4 Round corner channels
1.5.5 Additional effects
1.6 Outlet channel
1.6.1 Contact friction in outlet channel
1.6.2 Material flow
1.6.3 Movable channel walls
1.7 Inlet channel
1.7.1 Friction in the inlet channel
1.7.2 Stress distribution
1.7.3 Movable channel walls
1.8 ECAE of batch billets
1.8.1 Shapes of billets
1.8.2 Multi-pass processing
1.8.3 Processing parameters
1.8.4 Defects associated with ECAE
1.9 Continuous ECAE
1.9.1 Friction conditions
1.9.2 Plastic zone
1.9.3 Analysis of CECAE
1.10 Modifications of ECAE
1.11 Applications

2 Incremental ECAP
2.1 Concept of incremental ECAP (I-ECAP)
2.1.1 First idea
2.1.2 Process definition
2.1.3 Relation to ECAP
2.1.4 Place of I-ECAP in the metal-forming discipline
2.2 I-ECAP of square bars
2.2.1 FE simulation
2.2.2 Tooling
2.2.3 Machine
2.2.4 Controls
2.2.5 Results
2.3 I-ECAP of plates
2.4 I-ECAP of sheets
2.5 ECAP/I-ECAP with converging billets
2.6 I-ECAP of tubes
2.7 Incremental angular splitting
2.8 Summary

3 Tooling for ECAP
3.1 General recommendations for process design
3.2 Configuration of ECAP channel
3.2.1 Inclination angle
3.2.2 Cross-section
3.2.3 Number of turns along channel
3.3 Reduction of friction
3.3.1 Movable die parts
3.3.2 Common face pressing
3.3.3 Lubrication
3.4 Die design
3.4.1 Bolted dies
3.4.2 Split dies
3.4.3 Prestressed dies
3.5 Punch design
3.6 Tool materials for die and punch
3.7 Working conditions
3.8 Monitoring of ECAP

4 High pressure torsion (HPT)
4.1 Introduction
4.1.1 Unlimited strain
4.1.2 Efficiency of the technique
4.1.3 Simplicity of the process
4.1.4 Reliability of the technique
4.1.5 Flexibility of testing parameters
4.1.6 Versatility of high pressure torsion
4.1.7 Sufficient sample dimensions
4.2 Some characteristics of HPT microstructures
4.3 Principles of HPT: description of different setups
4.3.1 The idealised HPT version
4.3.2 Fully constrained HPT
4.3.3 Quasi-constrained HPT
4.4 Design criteria for building an HPT device
4.4.1 The test rig
4.4.2 Applied pressure
4.4.3 Applied torque
4.4.4 Anvil design and material selection
4.4.5 Tool failures
4.4.6 Attachments for HPT experiments
4.4.7 Upscaling of HPT
4.5 Outlook

5 Cyclic extrusion-compression (CEC)
5.1 Initial CEC device for unlimited deformation
5.2 Microstructural evolution during CEC
5.3 Force parameters of CEC processes
5.4 Effect of tool geometry on formation of shear bands
5.5 Special hydraulic press for CEC processes
5.6 Grain refinement in Al6082 alloy
5.6.1  Evolution of shear bands under varying backpressure
5.6.2 Evolution of microstructure of Al6082 alloy
5.6.3 Finite element simulation of CEC processes
5.6.4 Stress path analysis in CEC processes
5.6.5 Stress state in the deformation zone
5.7 Plastic consolidation of metallic powder materials

6 Twist extrusion (TE)
6.1 Introduction and historical retrospective
6.2 Mechanics of plastic flow in TE
6.2.1 Characteristic properties of deformation in TE
6.2.2 Stress-strain state in TE
6.3 TE as a processing technique
6.3.1  Principal equations for estimating processing  characteristics
6.3.2 Industrial prototype of TE machine
6.4  Formation of structure and properties for different applications
6.4.1 Major effects of TE
6.4.2 Applications of TE
6.5 Recent developments in TE and its derivatives
6.5.1 Planar TE
6.5.2 Laboratory horizontal tool set for TE

7 Accumulative roll-bonding (ARB)
7.1 Introduction
7.2 Background of development and principles of ARB process
7.3 Nanostructures obtained by ARB
7.4 Summary

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