Aluminum-lithium alloys. Eswara Prasad, Properties, and applications : processing, properties, and applications

643 Pages·2013·24.18 MB·English

Aluminum(cid:1)Lithium Alloys
Aluminum(cid:1)Lithium
Alloys
Processing, Properties, and Applications
N. Eswara Prasad
Amol A. Gokhale
R.J.H. Wanhill
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Foreword
The demand for lightweight structural ele-
ments is perennial, particularly for aerospace
applications. Lithium is the lightest metallic
element, and thus offers stellar advantages as
an alloying element in aluminum, the primary
structural material for light-alloy based
aerospace structures. Each unit addition of Li
reduces the density of Al alloys by about 3%
and enhances the elastic modulus by about
6%, besides contributing to enhanced tensile
strength accompanied by improved high cycle
fatigue as well as fatigue crack growth
resistance. The strength(cid:1)fracture toughness
combination at cryogenic temperatures is also superior in Al(cid:1)Li alloys.
However, there are considerable challenges in practically realizing the
above-stated advantages. As an alkali metal, Li is highly reactive and harms
any surface with which it comes into contact. Therefore, innovative melting
and casting technologies must be used to make Al(cid:1)Li alloy products.
Moreover, Al(cid:1)Li alloys require stringent composition control and have
narrow process windowsfor obtaining optimum properties.
Intense international R&D efforts over the past two decades have
addressed a whole range of issues related to making, shaping, and treating
Al(cid:1)Li alloys. As a result, the following have been notably established:
(i) production technologies for large scale melting and casting Al(cid:1)Li alloys
with optimized chemistry, (ii) advanced processing based on process model-
ing, (iii) thermal and thermomechanical treatments to achieve the desired
microstructure(cid:1)mechanical property (strength and fracture toughness as well
as fatigue and crack growth resistance) combinations, and (iv) fabrication
technologies, including superplastic forming and friction stir welding. As a
consequence, numerous patented Al(cid:1)Li alloys have been commercially pro-
duced in different product forms. These alloys possess, in comparison to the
traditional 2XXX and 7XXX series Al alloys, higher modulus (15(cid:1)25%) and
higherspecificstrength(8(cid:1)15%),andthereforeprovideaeronauticaldesigners
an opportunity to significantly reduce the weight of aeronautical and space
structuresforensuringenhancedfuelefficienciesandhigherpayloads.
The present volume systematically documents how a vast array of pro-
blems have been overcome to enable significant progress in diverse technical
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areas to realize production and deployment of Al(cid:1)Li alloys. All the authors
have had long-standing experience with this relatively more difficult class of
Al alloys, with noteworthy original findings to their credit. Beginning with
a superb outline of the historical development, the introductory part (first
2 chapters) summarizes the present status of Al(cid:1)Li alloys and describes
aspects of aerostructural design in the context of their application. In the
subsequent four parts, various aspects of physical metallurgy (3 chapters),
processing (4 chapters), mechanical behavior (5 chapters), and applications
(2 chapters) of Al(cid:1)Li alloys are dealt with. It is particularly pleasing for me
to see that several contributing authors and two of the three editors are from
the Indian Defence Metallurgical Research Laboratory with which I was
associated three decades ago, just about when Al(cid:1)Li alloys were beginning
toattract international attention.
Thisthoughtfully editedbookofinformativearticlesonAl(cid:1)Liclearlypro-
misestobeoneofthemostimportantreferencevolumesonthesescientifically
intriguingandtechnologicallychallengingalloys.
P. Rama Rao
FNAE, FNA, FASc., FNASc, FREng., Foreign Associate NAE (US),
FTWAS,FUAS
PresentlyChairman, Governing Council, ARCI, PO Balapur,
Hyderabad, India
FormerDirector, DefenceMetallurgicalResearchLaboratory, DRDO,
Hyderabad, India
FormerSecretary,DepartmentofScience and Technology(DST),
Government ofIndia,New Delhi, India
FormerChairman, Atomic Energy Regulatory Body, Government ofIndia,
Mumbai,India, FormerVC, University of Hyderabad (UoH),
Hyderabad, India
Former President ofIIM, ISCA, IAS, INAE, MRSI,ICF,IUMSand
Present President, IndianNuclear Society, India
Preface
The history of aluminum(cid:1)lithium (Al(cid:1)Li) alloys goes back to the 1920s,
but it is only since the 1990s that the fundamental understanding of these
alloys has matured and enabled the development of a family of alloys with
excellent combinations of engineering properties. These are the so-called
third generation Al(cid:1)Li alloys, and excellent property combinations are
required for them to compete in the “high-tech” field of aerospace structures
with establishedconventional aluminum alloys and carbon-fibercomposites.
ThisbooksurveystheknowledgeaboutAl(cid:1)Lialloysandtheirdevelopment,
concentratingonthesecond-andthird-generationalloys.Thesecond-generation
alloyswerelargelyunsuccessfulfromanengineeringpropertyviewpoint,butthe
lessonslearnedfromtheirdevelopmentinthe1970sand1980shavebeenessen-
tialindefiningandestablishingthethird-generationAl(cid:1)Lialloys.
Thebook is divided into the following main parts:
(cid:1) Part I: Introduction toAl(cid:1)LiAlloys (Chapters1 and 2)
(cid:1) Part II: Physical Metallurgy (Chapters 3(cid:1)5)
(cid:1) Part III: ProcessingTechnologies (Chapters 6(cid:1)9)
(cid:1) Part IV:Mechanical Behavior(Chapters 10(cid:1)14)
(cid:1) Part V: Applications (Chapters 15 and16)
Each chapter discusses a specific topic, which is summarized in the last
section of the chapter. References to the literature are added to each chapter
rather than collectively at the end of the book. The scope is such that many
authors were needed, generally more than one author for each chapter, and
their contributionsare acknowledged by the editors.
ThecurrentpaceofAl(cid:1)Lialloycommercialdevelopmentissuchthatthis
bookwillinevitablybecomeoutdatedwithinthenextfewyears.Nevertheless,
wehopeitwillprovideavaluablereferenceworkfortheforeseeablefuture.
Republic ofIndia andthe Netherlands
September, 2013
xvii
About the Editors
N.EswaraPrasadobtainedB.Tech.(in1985)and
Ph.D. (in 1993) degrees in Metallurgical Engineering
from Indian Institute of Technology (BHU), Varanasi,
India, and joined the Indian Defence Research and
Development Organisation (DRDO) in 1985. Since
then, Dr. Prasad worked in the fields of Design,
Development, Life Prediction, and Airworthiness
Certificationleadingtotheproductionofaero-materials,
namely Al and Al(cid:1)Li alloys; Mo and Ti intermetal-
lics; aero Steels; Ti- and Ni-based high temperature
alloys; monolithic ceramics such as structural alumina, graphite, and SiC;
carbon, silica, and SiC-based Continuous Fiber-reinforced, Ceramic-matrix
Composites (CFCCs).Hisresearch contributions areprincipally on thedefor-
mation behavior, fatigue power-law relationships, creep(cid:1)fatigue interactions
(CFI), and micromechanisms of fatigue and fracture. Dr. Prasad has authored
140peer-reviewedpublicationsandnearly200confidentialreportsandcertifi-
cation documents. Dr. Prasad is the recipient of several awards and recogni-
tions, including“YoungScientist” fromIndianScience CongressAssociation
in 1991, “Young Metallurgist” of Indian Institute of Metals for 1994,
“Humboldt Research Fellowship” from Alexander von Humboldt-Stiftung,
Bonn, Germany (1998(cid:1)1999), “Visiting Scientist” at Max-Planck-Institut fuer
Metallforschung, Stuttgart, Germany (1998(cid:1)1999), Binani Gold Medal of
Indian Institute of Metals (2006), “Metallurgist of the Year for 2010” by the
MinistryofSteel,GovernmentofIndia.Dr.PrasadisaFellowofInstitutionof
Engineers (FIE (cid:1) 2009), Fellow of Indian Institute of Metals (FIIM (cid:1) 2011),
and Fellow of Andhra Pradesh Akademi of Sciences (FAPASc (cid:1) 2011).
Dr. Prasad is presently the Regional Director of the Regional Centre for
MilitaryAirworthiness(Materials),CEMILACatHyderabad,India.
Amol A. Gokhale obtained a B.Tech. in
MetallurgicalEngineering,fromtheIndianInstituteof
Technology, Bombay, in 1978, and M.S. and a Ph.D.
in Metallurgical Engineering from the University of
Pittsburgh,Pittsburgh,USA,in1980and1985,respec-
tively. Since joining the Defence Metallurgical
Research Laboratory (DMRL) in 1985, Dr. Gokhale
led the development of second-generation Al(cid:1)Li
alloys for Indian defence for about 20 years, which
xix
xx AbouttheEditors
included collaborative efforts with VIAM and KUMZ in Russia, and ADA
and HAL in India to manufacture deep formed clad sheet products. He also
led the development of aluminum alloy castings for torpedoes and aluminum
foams for shock absorption applications. His most recent contributions are
in the development of materials and modules for hot structures of hypersonic
vehicles. He is working in association with Belarus Powder Metallurgy
Laboratory to develop Ni-based foams. Important awards received by
Dr. Gokhale include the National Research and Development Corporation
“Technology Innovation” Award (1994), the “Metallurgist of the Year
Award” by the Ministry of Steel (2000), the “DRDO Scientist of the Year”
award (2008), and the “GD Birla Gold Medal” from the Indian Institute
of Metals (2010). He has been a Fellow of the Indian National Academy of
Engineeringsince 2011.Hehaspublishedabout80technicalpapersandfiled
1 patent. Presently, Dr. Gokhale is the Director of the Defence Metallurgical
ResearchLaboratory,Hyderabad,India.
Russell Wanhill has a Ph.D. (1968) in Metallurgy
from the University of Manchester Institute of
Science and Technology, Manchester, UK, and a
DoctorofTechnicalSciencedegree(1995)fromDelft
University of Technology, Delft, The Netherlands. He
joined the National Aerospace Laboratory (NLR) of
the Netherlands in 1970 and since then has investi-
gated fatigue and fracture of all classes of aerospace
alloys, including many service failures. From 1978 to
1996 Russell was Head of the Materials Department
of the NLR, and in 1979(cid:1)1980 adjunct Professor of materials at Delft
University of Technology. He is the co-author of the book “Fracture
Mechanics” (1984), which is now into a second edition, and has written more
than320reportsandpublications.FromNovember2009toMay2010,Russell
was a “Visiting Academic” at the Defence Science and Technology
Organisation, DSTO, Melbourne, Australia. His collaboration with DSTO col-
leagues has resulted in journal publications, four book chapters (including one
in the present book), a monograph, and a 1-day failure analysis course. Since
1994Russellhasinvestigatedtheembrittlementofancientsilverandpublished
a number of papers on this seemingly esoteric but serious problem. “In 2002
the Board of the Foundation NLR awarded Russell the first Dr. ir. B.M. Spee
Prizeforoutstandingcontributionsinthefieldofaerospacematerials”.Russell
is presently Emeritus Principal Research Scientist in the Aerospace Vehicles
DivisionoftheNLR.
A Note of Gratitude from
the Editors
The present monograph deals with the past, present, and future of one of the
most exiting alloys to emerge in recent decades that have a vast potential for
aeronautical applications—namely the aluminum(cid:1)lithium (Al(cid:1)Li) alloys—
and highlights the aspects of alloy processing, mechanical behavior, and
properties and aerospace applications. Such an arduous task is not easy to
accomplish without the total support and whole-hearted participation of all
the authors and members of book editorial offices at Hyderabad, India, and
Elsevier, New York. We wish to profoundly thank each one of them—
Professor Edgar A. Starke, Jr., Professor T.R. Ramachandran, Dr. K. Satya
Prasad, Dr. Kumar V. Jata, Dr. Vijaya Singh, Dr. G. Jagan Reddy, Dr. S.B.
Prabu, Professor K.A. Padmanabhan, Dr. G. Madhusudhan Reddy, Professor
T.S. Srivatsan, Professor Enrique J. Lavernia, Professor V.V. Kutumbarao,
Dr. G. Malakondaiah, Professor S.P. Lynch, Dr. Gary H. Bray, Dr. N.J.
Henry Holroyd, Professor Roger C. Newman, Dr. A.K. Vasudevan, Mr. B.
Saha, Mr. G. Gouda, Dr. K. Tamilmani, and Members, Hyderabad Book
Secretariat Mr. Y. Balaji, Mr. Ch.V.A. Narasayya, Mrs. M. Swarna Bai, Mrs.
C. Poornia, and Ms. P. Varsha. We are deeply beholden to Professor Palle
Rama Rao, Distinguished Scientist, who led the Al(cid:1)Li alloy development
program inIndia,for the exquisite Foreword.
Most of the authors of this book had in their past authored or guided
doctoral theses based on works on Al(cid:1)Li alloys, which include several years
of research, development, production, and certification. Some of them have
also painstakingly reviewed the book chapters. Notable in this effort are:
Professor Ed Starke reviewing the book chapter on Aero-Structural Design;
Dr. Kota Harinarayana and Mr. P.S. Subramanyam on Aero-Structural
Design and Aero Certification; Professor David Laughlin on Phase Diagrams
and Phase Reactions; Professor T.R. Ramachandran on Microstructure
Evolution and Melting and Casting; Dr. Vikas Kumar on Fatigue Crack
Growth, and Dr. S.V. Kamat on Fracture Toughness. We owe our profound
gratitudetoall these contributingreviewers.
Thescientific,technological,anddesigndataofseveralaluminum(cid:1)lithium
alloys have been shared magnanimously by several authors, especially those
concerned withthird generationAl(cid:1)Li alloys.Infact, there was a stage inthe
book project that there could be no further progress without the inputs
on third generation Al(cid:1)Li alloys. The support of Professor Ed Starke and
xxi
xxii ANoteofGratitudefromtheEditors
Dr. Gary H. Bray at this crucial juncture proved critical as this very support
alone had advanced the book project further to its completion. In this context,
wealsothankalltheauthorsofcitedpublications,whohavegenerouslyallowed
ustoincludetheirdataandschematicsinthepresentbook.
Finally, it is a great pleasure to acknowledge the professional support by
the Elsevier Team—particularly, Mr. StephenP. Merken, Acquisitions Editor
(person having involved at all stages of book publication), Ms. Amorette
Padersen, Vice President, Marketing, and all the members of Book Design
Team,headed by Mr. JeffreyM. Freeland, Editorial Project Manager.
Republic of India andthe Netherlands
September, 2013