Light Alloys: Directory and Databook

526 Pages·1998·19.376 MB·English

by  Bob Hussey, Jo Wilson (auth.)

LIGHT
ALLOYS
DIRECTORY AND DATABOOK
Compiled by Bob Hussey and Jo Wilson
RJ Technical Consultants
Charente Maritime
France
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llli.il_J
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
First edition 1998
© 1998 Springer Science+Business Media Dordrecht
Originally published by Chapman & Hall in 1998
ISBN 978-0-412-80410-6 ISBN 978-1-4615-5777-7 (eBook)
DOI 10.1007/978-1-4615-5777-7
Ali rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted
in any form or by any means, electronic, mechanical, photocopying, record ing or otherwise, without the prior
written permission of the publishers. Applications for permission should be addressed to the rights manager at
the London address of the publisher.
The publisher makes no representation, express or implied, with regard to the accuracy of the information
contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that
may be made.
A catalogue record for this book is available from the British Library
= Printed on acid-free text paper, manufactured in accordance with ANSIINISO Z39.48-1992
(Permanence of Paper).
Preface
The overall aim of this book is to aid the selection and standards and specifications, with that provided by
sourcing of Aluminium, Magnesium, Titanium and Beryllium contributors to the book (commercial or proprietory
alloys - known collectively, for the purposes of this book, as data). Under no circumstances should the data given in
"Light Alloys". Concise, relevant technical data is provided this book be used for design purposes. It is there to
for these. Also included are commercially available metal provide an indication of the capabilities of particular
matrix composites (using light alloy matrices) and hybrid materials for general comparison purposes and as an
polymer-metal laminates. World-wide commercial sources aid to general materials selection. The following data
for these metals and alloys are given together with detailed (where available) is presented for each alloy
information on the suppliers. designation:
• Chemical composition.
THE STRUCTURE OF THIS BOOK • Identified product forms.
• Similar/Equivalent alloys.
The book is divided into four main parts:
o Part 1 - Review: • Notes on characteristics, applications, etc.
• Typical mechanical properties, for specific tempers,
• A broad introduction to light metal alloys and their
conditions and product forms.
applications.
• Effects of alloying additions and impurities. Part 4 - Appendices:
• Alloy and Temper Designation Systems • Standards - provides a listing of standards and
explanation of the various systems cited in the specifications which are applicable to light alloy
book, both nationally-based designation systems grades. For each base metal, the list is divided into
and those international systems which have been national and international standards organisations,
adopted within industry. e.g. CEN, AA, ISO, BS, SAE, NF, etc.
• Processing methods. • Primary aluminium producers - listed by country.
• Glossary - a compilation of technical terms
• Reading list.
appropriate to light alloys and their use.
Part 2 - Directory: Contains a comprehensive listing
• Multilingual vocabulary - Technical keywords are
of manufacturers and suppliers, their product ranges,
given in English, French, German, Italian and
tradenames and contact details for all those included in
Spanish.
this edition.
• Conversion Factors & Units - Metric units are used
• Suppliers Product Types -a table showing the
throughout this book.
product forms, processing methods and alloy types
for each supplier. Indexes:
• Tradenames -A listing of trade names for each • Alloy designation cross-reference index.
supplier. • Alloy designations/names index.
• Suppliers by Country -Supplier names organised Note:
by country. The information presented in this book has been compiled
• Group Affiliations -A listing of companies organised from a variety of sources: manufacturers, agents and
by group company name (where known) and suppliers; trade associations; official bodies and standards
country. organisations. Great care has been taken to ensure that all
of the information is accurately represented here, but no
• Supplier Details -The entry for each company, or
responsibility can be taken for errors or omissions.
division, describes their activities and the alloys and
For this first edition, we have tried to include the largest
forms available. It also summarises other related
possible number of manufacturers, suppliers and products.
activities, along with Quality Approvals and any
Inevitably some will have been missed, so any comments on
other information of interest.
alterations or additions would be very useful. The final page
• Other useful address and data sources.
of the book shows how to contact the authors.
o Part 3 - Alloy Information: Divided into sections for
each base metal. Information on MMC's is included,
although the data available is more proprietory in
nature. The information within this section is a
combination of that contained in various applicable
ACKNOWLEDGEMENTS
We wish to thank Roger Davies and Dave Bashford for
their considerable assistance throughout the compiling of
this book. Peter Caton for providing us with an insight
into magnesium alloys from his wide industrial
experience. Dr Barrie Dunn for his support and
encouragement. The International Magnesium
Association (IMA) , the Aluminium Federation (ALFED,
UK) and the International Titanium Association (ITA)
made their membership lists available free of charge.
The Aluminum Association (AA, USA) registration lists
were of particular value in compiling and checking the
aluminium alloy data sections.
Thanks are also due to the many others who replied
promptly to our requests for information. If only all
organisations were the same.
CONTENTS
PRE F ACE --------------------------------------------------- iii Further Reading --------------------------------------------------- 13
Boo ks ------------------------------------------------------------ 1 3
The structure of this book ---------------------------------------- iii
Metallurgy & Properties------------------------------ 13
Acknowledgements ------------------------------------------------ iv Applications & Usage -------------------------------- 15
Processing ---------------------------------------------- 15
CONTENTS -------------------------------------------------- v
Joining --------------------------------------------------- 16
PART 1 - REVIEW ----------------------------------------- 1 Safety----------------------------------------------------- 16
Conference Proceedings ---------------------------- 16
I ntrod ucti 0 n ---------------------------------------------------------- Commerce ---------------------------------------------- 17
Alloy Characteristics ----------------------------------------------- J ou rnals --------------------------------------------------------- 17
AI u min i u m Alloys---------------------------------------------- Electronic / Audio-visual Products ----------------------- 18
General Properties of Aluminium ------------------
Casting Alloys ------------------------------------------- 2 PART 2 - DIRECTORY --------------------------------- 21
Wroug ht Alloys ------------------------------------------ 2 Manufacturers' Product Ranges------------------------------- 21
Aluminium Lithium Alloys ----------------------------- 2
Trade Names & Standard Product Codes ------------------ 27
Magnesium Alloys --------------------------------------------- 3
Structure and Properties ------------------------------ 3 Manufacturers & Suppliers - Countries --------------------- 29
Tita ni u m Alloys ------------------------------------------------- 3 Group Affiliations -------------------------------------------------- 33
Commercially Pure Titanium------------------------- 4
Manufacturers & Suppliers - Addresses -------------------- 40
Alpha Titanium Alloys---------------------------------- 4
Alpha-Beta Titanium Alloys -------------------------- 4 Useful Addresses ----------------------------------------------- 122
Beta Titanium Alloys ----------------------------------- 4
PART 3 - ALLOY INFORMATION ----------------- 141
Be ryll i u m --------------------------------------------------------- 4
Key ------------------------------------------------------------------ 141
Forms and Processing Methods -------------------- 5
Metal Matrix Composites (MMC's) ------------------------ 5 Aluminium (Wrought)------------------------------------------- 143
Aluminium-based MMC's ----------------------------- 5 Aluminium (Casting) -------------------------------------------- 233
Magnesium-based MMC's---------------------------- 6
Alu m inium (Powder) -------------------------------------------- 295
Titan i um-based MMC's-------------------------------- 6
Hybrid Metal-Polymer Laminates -------------------------- 6 Magnesium ------------------------------------------------------- 297
Effects of Alloying Elements & Impurities -------------------- 6 Titan i u m ----------------------------------------------------------- 31 7
Alloy Designation Systems--------------------------------------- 9 Beryllium ---------------------------------------------------------- 345
Alu m in i um Alloys----------------------------------------------- 9 PART 4 - APPENDICES------------------------------ 351
Wrought --------------------------------------------------- 9
Cast ------------------------------------------------------ 10 A - Standards & Specifications------------------------------ 352
Magnesium Alloys -------------------------------------------- 11 B - World Aluminium Production---------------------------- 410
Titanium Alloys ------------------------------------------------ 11 C - Glossary ----------------------------------------------------- 413
Beryllium -------------------------------------------------------- 11
D - Multilingual Vocabulary:
Processing Methods ---------------------------------------------- 12 English -French -German -Italian -Spanish------- 418
Conventional Techniques----------------------------------- 12
E - Conversion Factors --------------------------------------- 424
Rapid Solidification Processing (RSP) ------------------ 12
Thixocasting / Rheocasting -------------------------------- 12 INDEXES -------------------------------------------------- 427
Superplastic Forming ---------------------------------------- 12 Alloy Cross-references ---------------------------------------- 427
Powder Metallurgy-------------------------------------------- 12 Alloy Designations ---------------------------------------------- 505
Call for Contributions------------------------------------------- 527
Part 1 • Review
•
The metals and their numerous alloys are very well
INTRODUCTION
characterised and, with the exception of Beryllium, widely
accepted as engineering materials. Some alloy and
Within the context of this book, a "Light Alloy" is a metallic processing development continues to occur, but generally
system based on aluminium, magnesium, titanium or these are mature materials with a wide knowledge base.
beryllium. This definition includes metal matrix composites Innovations tend to be in the field of materials processing
(MMC's), where the matrix is one of the light alloys, and the and in the development of reinforced and laminated alloys.
growing family of hybrid metal/polymer laminated materials.
Aluminium Alloys
This book concentrates on the availability and basic
properties of commercial alloys. A great deal has already
been written on the metallurgy, characteristics and Aluminium has excellent corrosion resistance and electrical
applications of these, and there is no real need to repeat it conductivity. It is easily formed or cast and a very large
here. What follows is a brief review of characteristics, for number of commercial alloys are available.
more detailed technical and scientific information see the
There are a vast number of applications, ranging from
extensive reading list at the end of this section.
packaging (e.g. beverage cans, household foil) to whole
aircraft structures. Architectural uses are very widespread.
ALLOY CHARACTERISTICS Vehicle manufacturers, increasingly conscious of weight,
are moving towards maximising aluminium-based engines
The particular characteristics which tend to encourage the and whole body structures.
use of light alloys are:
General Properties of Aluminium
o High specific strengths (strength/specific gravity ratiO)
Light alloys are used in many weight-critical applications, The beneficial characteristics of aluminium include:
e.g. high speed components, light-weight constructions, o high electrical conductivity,
automotive and aerospace structures. Table 1 shows a
comparison of some basic material properties with those o high thermal conductivity,
of steel. o excellent resistance to oxidation,
o Very good processability by a wide range of mechanical o excellent resistance to corrosion,
working and casting techniques. Processing
o nonmagnetic (paramagnetic) behaviour.
temperatures are much lower than for example steel, but
their service temperatures are limited similarly. Aluminium reacts with oxygen, even at room temperature, to
o Atmospheric corrosion resistance is generally very good produce an extremely thin, coherent aluminium oxide
and the high chemical resistance of titanium makes it (AI203) layer that protects the underlying metal from
widely used for chemical plant with aggressive media. corrosion. This characteristic is exploited and enhanced in
o All light alloys are enthusiastically recycled. Initial anodising, whereby a wide range of protective or decorative
finishes are possible.
extraction costs are quite high, but, because of the low
melting points, reprocessing costs are relatively low. Limitations on the use of aluminium alloys are:
o no fatigue limit, so failure by fatigue can eventually occur
even at low stresses.
Specific
Specific Modulus UTS Strength o poor elevated temperature performance leading to the
Alloys Gravity (GPa) (MPa) (MPa) loss of mechanical properties as a result of over-ageing
or recrystallization.
Steel 7.9 160 -220 250 -2400 30 -310
Aluminium 2.7 65 -75 50 -600 25 -230 o low hardness; poor wear resistance.
Magnesium 1.75 40 -50 75 -400 80 -225 o some alloys and environments may give poor corrosion
Titanium 4.5 95 -135 240 -1450 80 -380 resistance.
Beryllium 1.85 290 -305 240 -800 130 -430
Table 1 -Comparison of basic properties.
B. Hussey et al., Light Alloys
© Springer Science+Business Media Dordrecht 1998
2 Review
Aluminium alloy compositions are initially grouped as either Fast cooling, obtained in die casting or permanent mould
'casting' or 'wrought', (very few alloys can be processed by casting, increases strength by refining grain size and the
both methods): eutectic microconstituent.
D Casting alloys can be tailored for specific casting Grain refinement by alloying is also used to improve the
methods; e.g. sand, permanent mould, die-casting. The microstructure, hence the level of disperSion strengthening.
alloy composition and casting method affects the final Depending on the alloy, this may be achieved by additions
metal structure. Some may be modified by subsequent of:
heat-treatments to improve properties.
D boron and titanium.
o Wrought alloys are shaped by plastic deformation (hot
D sodium or strontium -to change the eutectic structure.
and/or cold working). They have compositions and
microstructures Significantly different from casting alloys D phosphorus -hardening and refining primary silicon.
owing to the different requirements of the manufacturing
[See: Effects of Alloying Elements and Impurities]
process.
Within each major group the alloys can be divided into two Wrought Alloys
subgroups: heat-treatable and non heat-treatable alloys.
Commercial alloys are strengthened either by strain (work) As with cast aluminium alloys, commercial compositions fall
hardening or by heat treatment (age hardening); this can into a number of broad groups. This is again reflected in the
produce strengths in excess of 30 times that of pure, soft AA alloy designation system, which is now almost
aluminium. The degree of strengthening is known as universally used to describe these alloys -[See Alloy
condition or temper and is generally indicated by a suffix to Designation Systems]. Table 3 shows these compositional
the alloy code The most widely found system uses the categories.
following letters to indicate the nature of the treatment:
Composition Strengthening AA Alloys
D 0 = Annealed (soft)
CPAI >99% Not age hardenable 1xxx
D T = Heat-treated AI-Cu; AI-Cu-Li Age hardenable 2xxx
o H = Strain hardened AI-Mn Not age hardenable 3xxx
D F = As-finished (no specific treatment -the properties AI-Si; AI-Mg-Si Age hardenable (Mg) 4xxx
obtained depend on the forming method used)
AI-Mg Not age hardenable 5xxx
Numbers following the T or H indicate the amount of strain AI-Mg-Si Age hardenable 6xxx
hardening and the exact type of heat treatment or other AI-Mg-Zn Age hardenable 7xxx
special aspects of the processing of the alloy. Variations
may exist within Nationally-based systems. [See: Alloy AI-Li, Sn, Zr, B, Mostly age hardenable 8xxx
Fe or Cu
Designation systems].
Table 3 - Aluminium Wrought Alloy Types
Casting Alloys
The 1x xx and 3xxx series are single-phase alloys, except for
Commercially available aluminium casting alloys fall into minor inclusions or intermetallic compounds. Their
several compositional groups. These groupings indicate properties are determined by strain hardening, limited solid
whether subsequent hardening heat treatments are solution strengthening and grain-Size control.
possible. As is shown in Table 2, they are also reflected in
the Aluminum Association codes for these alloys [See: Alloy The 2xxx, 6xxx, and 7xxx series are age-hardenable alloys
and can be heat treated to produce excellent strengths.
Designation Systems].
They cannot be used at temperatures above -175°C in the
Composition Strengthening AA Alloys aged condition.
CPAI Not age hardenable 1xx
4xxx series are two phase alloys:
AI-Cu Age hardenable 2xx
AI-Si-Cu; AI-Mg-Si Some age hardenable 3xx D Alpha
AI-Si Not age hardenable 4xx D Beta -nearly pure silicon.
AI-Mg Not age hardenable 5xx
The alloys containing both Si and Mg can be age-hardened
AI-Mg-Zn Age hardenable 7xx
by precipitation of Mg2Si.
AI-Sn Age hardenable 8xx
5xxx alloys are two phase at RT:
Table 2 - Aluminium Casting Alloy Types
D Alpha, a solid solution of magnesium in aluminium,
The majority of commerCially used aluminium casting alloys o Mg2Ab, a hard, brittle intenmetallic compound.
come from the groups containing sufficient silicon to cause
the eutectic reaction. This gives alloys with particularly low AI-Mg alloys are strengthened by a fine dispersion of Mg2Ab
melting pOints, good fluidity (flow in the mould without as well as by strain hardening, solid solution strengthening
premature solidification), and good castability. and grain-size control. Age-hardening treatments are not
possible because the Mg2Ab is not coherent.
The properties of the AI-Si alloys are controlled by:
D solid solution strengthening of the alpha aluminium Aluminium-Lithium Alloys
matrix.
Alloys containing lithium have been introduced, particularly
D dispersion strengthening by the beta-phase.
for the aerospace industry. As Li additions are lower than
D solidification characteristics (control of the primary grain the other main alloying elements they are dispersed
size, shape plus the nature of the eutectic amongst the 2xxx, 7xxx and 8xxx wrought aluminium series.
microconstituent).
Review 3
The addition of lithium can give significant improvements in strengthening is possible. However the solubility increases
mechanical properties, but may compromise other with temperature allowing many alloys to be strengthened
characteristics: by either dispersion strengthening or age hardening.
IJ The low density of lithium gives a reduction in alloy Age-hardened magnesium alloys (containing Zr, Th, Ag, or
density (can be 10% less). Ce) can have good resistance to over-ageing at
IJ Increased elastic moduli. temperatures as high as 300°C.
IJ Strength equals or exceeds conventional alloys. Alloys containing up to 9% lithium have exceptionally low
densities.
IJ Improved fatigue resistance (slow fatigue crack growth
rate). To improve the generally poor corrosion performance, some
IJ Good toughness at cryogenic temperatures. magnesium alloys have very low levels of impurities or
contain large amounts (>5%) of rare earth (RE) elements.
IJ Can be superplastically formed into complex shapes.
These alloys form a protective MgO film.
IJ Can be prone to stress corrosion cracking (SCC); varies
with other alloying elements and levels. The SCC Titanium Alloys
resistance can be improved by specific heat-treatments,
although the strength may be compromised.
Titanium alloys have intermediate densities and temperature
The high specific strength and specific stiffness makes resistance, along with excellent corrosion resistance. They
these alloys useful for aerospace structural applications, are widely used for applications in aerospace and chemical
e.g. floors, skins, and frames in military and commercial processing. Many of the alloys show a powerful response to
aircraft. strengthening by age hardening and quench and temper
heat treatments.
The high strength of AI-Li alloys results from age-hardening.
Alloys containing up to 2.5% Li can be heat-treated by Titanium alloys have:
conventional methods. Additional Li (up to 4%) can be IJ high specific strength
introduced by rapid solidification processing; further
IJ high specific stiffness
enhancing light weight and maximum strength.
IJ good high-temperature properties
Magnesium Alloys LJ excellent resistance to corrosion and contamination
below 535°C owing to an adherent, protective Ti02 film.
Magnesium is often extracted electrolytically from Above 535°C, the oxide film breaks down and small
concentrated magnesium chloride in seawater. It melts at a atoms such as carbon, oxygen, nitrogen, and hydrogen
slightly lower temperature than aluminium. embrittle the metal.
IJ Good speCific strength. The excellent corrosion resistance provides applications in
U Corrosion resistance (many environments) similar to chemical processing equipment, marine components, and
aluminium. biomedical implants. It is an important aerospace material
and is used for airframe and jet engine components.
IJ Very low density.
Owing to its high affinity for oxygen and other gases, any
IJ Very good casting characteristics.
melting and casting processes must be carried out under
CJ Low modulus. vacuum.
::J Low level of strengthening mechanisms.
Pure titanium is allotropic, with an HCP crystal structure
IJ Poor elevated temperature properties. (alpha) at low temperatures and a BCC structure (beta)
above 882°C. Alloying elements provide solid solution
IJ Poor fatigue resistance.
strengthening and change the allotropic transformation
IJ Poor creep resistance. temperature (alpha-beta transition) [See also: Effects of
IJ Poor wear resistance. Alloying Elements and Impurities]. The effects include
IJ Poor tolerance of salt-containing environments. IJ solid solution strengthening without affecting the
transformation temperature (Sn, Zr).
IJ Poses a hazard during casting and machining (combines
readily with oxygen and burns). IJ increase in alpha to beta transformation temperature by
alpha stabilising elements, (e.g. AI, 0, H).
Magnesium alloys are used in aerospace applications,
IJ decrease in transformation temperature; causing beta to
high-speed components, transportation and materials
be stable at RT, (beta stabilisers, e.g. V, Ta, Mo Nb).
handling equipment, portable equipment (mobile phones),
car components. IJ providing a eutectoid reaction which gives a two-phase
alpha-beta structure at RT (Mn, Cr, Fe).
Structure and Properties
In addition to the range of commercially pure grades and
Pure magnesium is generally less ductile than aluminium, conventional alloys, specialist titanium-based materials
but this may be increased by alloying. Some deformation include:
and strain hardening is possible at room temperature, and IJ Titanium-Niobium -a superconductive intermetallic
the alloys can be readily deformed at elevated compound.
temperatures. Strain hardening produces a relatively small
effect in pure magnesium because of the low IJ Titanium-Nickel -shows a shape-memory effect.
strain-hardening coefficient. IJ Titanium-Aluminium intermetallics (titanium aluminides)
which are being considered for some applications
The solubility of alloying elements in magnesium at room
requiring excellent high temperature characteristics;
temperature is limited; only a small degree of solid solution
mainly aerospace related.
4 Review
Commercially Pure Titanium Highly alloyed alpha-beta alloys are age-hardened.
D Quenched - the beta phase is retained as betass
Applications include heat exchangers, piping, reactors,
(supersaturated in Ti).
pumps, and valves for the chemical and petrochemical
industries. IJ Ageing - the betass precipitates alpha (Widmanstatten
structure) which improves the strength and fracture
D Superior corrosion resistance.
toughness.
D Impurities, such as oxygen, increase the strength of the
Some typical applications for the heat-treated alpha-beta
titanium (but reduce corrosion resistance).
alloys are aerospace components (airframes, rockets, jet
Alpha Titanium Alloys engines, landing gear). Some alloys, including Ti-6AI-4V,
can be superplastically formed.
This group commonly contain either 2.5% Cu or 5% AI +
Beta Titanium Alloys
2.5% Sn which provide solid solution strengthening to the
alpha phase. Alpha alloys are annealed at high temperature
None of the so-called beta alloys (usually containing V or
(beta), subsequent cooling determines the microstructure:
Mo additions) are entirely beta at RT. Instead, they are rich
D rapid cooling gives an acicular (Widmanstatten) alpha in beta stabilisers, such that rapid cooling produces a
grain structure with good fatigue resistance. metastable all-beta RT structure. Strengthening is obtained
D furnace cooling gives a plate-like alpha structure with both from:
improved creep resistance. o large amounts of solid-solution-strengthening alloying
elements.
Copper containing alloys may also show some precipitation
hardening. o ageing the metastable beta structure to allow alpha to
precipitate.
Near-Alpha Alloys
Applications include high-strength fasteners, beams, and
A complex group of compositions where the microstructural other fittings for aerospace applications.
constituents are determined by heat treatment. Alloys may
be alpha or alpha + beta. Processing adjustments can be Beryllium Alloys
used to improve particular properties, e.g. high temperature
properties for engine applications. Beryllium has an exceptional strength-to-weight ratio,
maintains its strength at high temperatures and is very stiff.
Alpha-Beta Titanium Alloys
Properties of commercial alloys are highly anisotropic.
A balance of alpha and beta stabilisers produces a mixture It is extracted from bertrandite (low-grade) and beryl (high
of alpha and beta phases at RT. The most alloy common of grade) ores by wet chemical techniques to give beryllium
this type is Ti-6AI-4V. Because the alloys contain two hydroxide. This is then converted into primary metallic
phases, heat treatments can be used to control and modify beryllium 'pebbles' by reduction using magnesium. These
the microstructure and properties. are then vacuum melted to form ingots which are
subsequently processed into pure (98-99%) powders.
Annealing provides a combination of high ductility, uniform
properties, and good strength. The cooling rate then These powders (BeQ <2%) are vacuum hot-pressed into
determines the final microstructure, and has different effects shapes and subsequently processed to semi-finished
on the two phases present: product forms. Recommended processing temperatures are
D Alpha: the alloy is heated just below the beta-transus 538-760°C; below 371°C brittleness is a problem.
temperature, permitting a small amount of alpha to The main characteristics of beryllium are:
remain and prevent grain growth:
o Lower density than aluminium.
• Slow cooling causes equiaxed alpha grains to
o Higher modulus (stiffer) than steel.
form; good ductility and formability while inhibiting
fatigue cracks from nucleating. o High speCific strength.
• Faster cooling, particularly from above the alpha o Low ductility (brittle).
beta transus temperature, produces an acicular or
o Maintains both strength and stiffness to high
'basket-weave' alpha phase. Fatigue cracks can
temperatures (>600°C). Useful mechanical properties
nucleate more easily in this, but crack growth is
are retained at elevated temperature to >800°C and
slower because of the complex structure (following
down to cryogenic temperatures.
the boundaries between alpha and beta phases);
good fracture toughness and creep resistance. o Transparency to electromagnetic radiation.
D Beta: two possible microstructures may be produced o Reactive.
when beta phase is quenched from high temperature:
U Expensive.
• Quenched -the beta transforms to titanium o Beryllium oxide is toxic.
martensite (alpha') in an alloy that crosses the Ms
line on cooling. The titanium martensite is a Beryllium has an HCP crystal structure giving limited
relatively soft, supersaturated phase. ductility at room temperature. When exposed to the
• Tempered -When alpha' is reheated beta is atmosphere at elevated temperatures, it rapidly oxidises to
precipitated from the supersaturated alpha' phase. form BeQ. These problems require the use of sophisticated
Fine beta precipitates initially increase the strength manufacturing techniques, such as vacuum casting, vacuum
compared with the alpha' (the opposite of a forging, and powder metallurgy. Consequently the majority
tempered steel martensite). Softening occurs when of beryllium components and structures are produced by
tempering is at too high a temperature. companies dedicated to working with the materials.
Review 5
Beryllium tends to be used for particular applications D Various protective coatings are possible to provide
exploiting a particular property rather than as a general protection in hostile environments:
engineering material, e.g.: • Proprietary 'Beryl coat' passivation coating;
D High specific stiffness (inertial guidance systems), Chromate conversion for salt-spray and high
temperature oxidation resistance.
D Structural properties in weight-critical applications;
aerospace applications, e.g. windshield components on • Anodising (chromic acid) -for corrosion protection,
the Space Shuttle, increase emissivity and reduce light reflection
(optical equipment).
D High-temperature stability, conductivity and low thermal
• Plating -not widely used, except for electroless
expansion are attractive for use in space,
nickel plating (polished surface of beryllium
D Specialist uses (X-ray windows in medical and analytical mirrors).
equipment, nuclear industry: neutron reflectors and
D Recycling -Clean scrap is recycled into new products by
moderators, etc.).
the major producer.
Rigorous safety procedures are required when working with
beryllium to avoid inhalation of metal particles and Metal Matrix Composites (MMC's)
compounds, including the oxide, which are toxic,
Owing to the specialist uses of beryllium, material In MMC's a reinforcement phase is incorporated into a metal
speCifications, where they exist, tend to be defence alloy. The reinforcement phase may be a particulate,
standards, e.g. MIL-B-8964 Sheet & plate, MIL-B-21531 whisker or continuous fibre. The aim is to produce a material
Bar, rod & shape. which retains some of the characteristics of the matrix (such
as ductility, formability, etc,) but has improved properties
Forms and Processing Methods (such as strength and stiffness) provided by the
reinforcement. All light metals, with the exception of
D Forging -possible. beryllium, have been considered as matrix phases for
D Rolling -possible, MMC's. Many alloy variants have been investigated with the
aim of improving mechanical properties, thermal stability
D Extrusion -possible.
and wear characteristics A number of combinations are
D Drawing -possible. now commercially available and have found applications
such as: engine components, pistons, braking system parts,
D Sheet -(cross-rolled) poor short-transverse properties
etc.
prevent forming at low temperatures. Processing is
normally carried out between 700-730°C; not >790°C or In general the size of particulate used for MMC's is much
original properties will be affected. larger than that used in oxide dispersion strengthened
D Plate and foil -possible (ODS) alloys.
DWire -possible Characteristics and processing parameters are determined
D Machining -using carbide tools. Surface damage from mainly by:
machining operations (which act as stress-raisers in D Matrix alloy.
load-bearing parts) require removal by etching. Chemical
D Reinforcement content.
milling, electro-chemical machining and Electro
discharge machining (EDM) avoid such mechanical D Chemical compatibility between a matrix and the
damage. Drilling may cause delamination and break-out reinforcement.
in sheet unless special precautions are taken, D Reinforcement/matrix bonding.
D Mechanical Joining -by rivets (squeeze-rivets only);
Manufacturing methods are usually adaptations of standard
bolting and threading. Press-fits need careful design to
metal processing techniques. These are generally powder
avoid damage.
metallurgical or casting in nature. Many of the techniques
D Brazing -with Zn-, AI-Si, Ag-based filler materials. Cu are patented and proprietary.
containing braze fillers may embrittle beryllium. SpeCial
techniques have been developed. Furnace brazing is Aluminium-based MMC's
done under vacuum to prevent oxidation. Dip-brazing is
also successful. Within the light-alloy matrix materials, aluminium-based
MMC's are probably the most advanced, The reinforcement
D Braze-welding -possible by TIG or MIG but requires a
is normally silicon carbide (particulate) for 'general
high level of welding skill.
engineering' applications, with some continuous fibre
D Diffusion bonding -possible reinforced MMC's for specialist aerospace applications.
Aluminium-based MMC's are now used in load-bearing
D Soldering -possible.
applications in the aerospace, automotive and leisure
D Welding (fusion) -not recommended, owing to cast grain industries. Within the electronics industry, MMC's are finding
structure in weld-zone, applications in electronic packaging, Here, characteristics
D Electron beam welding -successful for applications such as combined high-thermal conductivity and low thermal
without structural requirements (instrument assemblies). expansion are of interest for thermal management uses
(mainly high-power circuits; GaAs microwave devices). In
D Adhesive bonding -with proper surface preparation (acid
general, the reinforcement content is higher than for
cleaning and neutralising), reliable bonds have been
engineering applications. Net-shape manufacturing, where
produced for spacecraft assemblies.
the MMC is formed at the same time as the product is useful
for intricate components.