Extrusion of Aluminium Alloys / T. Sheppard
SELECTED CONTENTS:
Introduction
- The thermomechanical process
- Direct and indirect extrusion
– Direct extrusion
– Indirect extrusion - Extrusion of rods and solid shapes
- Extrusion of hollow sections
- The extrusion press
– Direct presses
– Indirect presses
Continuum principles
- Yielding and ductility
- Constitutive equations
- The extrusion pressure
- The friction coefficient
- Temperature models
– Temperature profile in the heated billet
– Heat balance in extrusion
– Finite-element modeling predictions
– Thermal balance during extrusion predicted by integral profile techniques - Diffusion
Metallurgical features affecting the extrusion of aluminium alloys
- Aluminium-alloy systems
- The DC cast state
- Homogenization
– Metallurgical consideration of homogenization - Thermal activation
- Recovery and recrystallization
– Dynamic recovery and dynamic recrystallization
– Microstructure - Recrystallization and layer thickness after solution soaking
- Quench sensitivity
Extrusion processing
- Introduction
- The Zener-Hollomon parameter and flow stress
– Flow stress
– Theoretical considerations
– Comparison of compression and torsion in material assessment - Material flow in extrusion
– The three types of flow - The pressure/displacement diagram
- The strain rate during extrusion
- Extrusion pressure – practical considerations
– The effect of friction
– The effect of the temperature-compensated strain rate
– The effect of section shape - Surface quality considerations
- Process-structure relationships
- Recrystallization
– Structure after extrusion
– Volume fraction recrystallization in the F-temper and after solution soaking - The relationship between process parameters and properties
- Material flow and inhomogeneity – structural considerations
– Development of structure in the extrusion container
– Substructural considerations
– Extrudate structure
– Subgrain size
– Development of dislocation structure related to peak: pressure - Press quenching and press solutionizing
– Introduction
– Metallurgical aspects
– Technological problems - Limit diagrams
Homogenization and extrusion conditions for specific alloys
- Introduction
- lXXX alloys
- 2XXX alloys
- 3XXX alloys
- 4XXX alloys
- 5XXX alloys
- 6XXX alloys
- 7XXX alloys
– AI-Zn-Mg alloys
– AI-Zn-Mg-Cu alloys - Aluminium-lithium alloys
- Extrudability, limit and productivity diagrams
– Extrudability
– Limit diagrams
– Productivity diagrams
Processing of 6XXX alloys
- Homogenization
– General principles of heat treatment - Alloys for specific applications
– High extrudability, general purpose alloys
– Medium-strength alloys - Factors affecting quench sensitivity
– Cooling rate
– Recrystallization inhibitors
– Toughness
– Structural sensitivity
– Quench sensitivity in welding - Surface problems and surface generation
– Introduction
– Surface features
– Extrusion topology (limit) diagrams
– Summary - Alternative metallurgical diagrams
– Possible phase transformations - Texture
- Extrusion defects
– Metallurgical factors affecting press productivity
– Recovery related defects
– Metallurgical defects visible after anodizing
Plant utilization
- Introduction
- The modem extrusion plant
– The extrusion press
– Ancillary equipment
– The extrusion process and parameter optimizing - Press requirements
– Reliability
– Mechanics
– Hydraulics
– Control and monitoring - Isothermal extrusion
– Process optimization
– Features required in a comprehensive process optimization
– Results of process optimization - Expert systems
– An expert system applied to an extrusion press
– A typical system description - Aspects of die design and correction
– Die stack considerations
– Die design steps
– Process factors to consider before modifying the die - Tool failure
– Characteristics
– Preventative measures - Scrap losses
– Extrusion losses
– Billet scrap - Extrusion control in manufacturing profiles of complex shapes
– Classification of complex shapes
– Improvement of billet quality
– Extrusion press alignment
– Extrusion condition - Product tolerance
– Die section
– Extrusion section
– Billet section
– Extrusion conditions
– Improvements in yield