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