Amorphous Metallic Alloys

540 Pages·1983·13.41 MB·English

by  Burton (Auth.)

Butterworths Monographs in Materials
The intention is to publish a series
of definitive monographs written
by internationally recognized
authorities in subjects at the
interface of the research interests
of the academic materials scientists
and the industrial materials
engineer.
Series editorial panel
M. Ashby FRS R. Kiessling
University of Cambridge Sveriges Mekanforbund, Stockholm
J. Charles H. Suzuki
University of Cambridge Tokyo Institute of Technology
A. G. Evans I. Tamura
University of California, Berkeley Kyoto University
M. C. Flemings G. Thomas
Massachusetts Institute of Technology University of California, Berkeley
R. I. Jaffee
Electric Power Research Institute,
Palo Alto, California
Already published
Die casting metallurgy
Control and analysis in iron and
steel making
Introduction to the physical
metallurgy of welding
Metals resources and energy
Forthcoming titles
Microorganisms and metal recovery
Eutectic solidification and processing
Control and analysis in steelmaking
Energy dispersive X-ray analysis of
materials
Mechanical properties of ceramics
Metallurgy of high speed steels
Residual stresses in metals
Continuous casting of aluminium
Butterworths Monographs in Materials
Amorphous Metallic Alloys
Edited by
F. E. LUBORSKY, PhD
Corporate Research and Development Center, General Electric Co., Schenectady, USA
Butterworths
London Boston Durban Singapore Sydney Toronto Wellington
All rights reserved. No part of this publication
may be reproduced or transmitted in any form
or by any means, including photocopying and
recording, without the written permission of
the copyright holder, application for which
should be addressed to the Publishers. Such
written permission must also be obtained
before any part of this publication is stored in
a retrieval system of any nature.
This book is sold subject to the Standard
Conditions of Sale of Net Books and may not
be re-sold n the UK below the net price given
by the Publishers in their current price list.
First published 1983
Butterworth & Co (Publishers) Ltd., 1983
British Library Cataloguing in Publication Data
Amorphous metallic alloys.—(Butterworths monographs
in materials)
1. Alloys
I. Luborsky, F. E.
546,.37 TN690
ISBN 0-408-11030-9
Typeset by MS Filmsetting Ltd., Frome, Somerset
Printed and Bound in Great Britain by Butler & Tanner Ltd., London & Frome
Preface
This book on amorphous metallic alloys is intended for the student and
researcher. It covers the preparation and properties of alloys produced by rapid
quenching from the molten state; it does not cover in any detail alloys prepared by
vacuum deposition, electro- or electroless-deposition or by sputtering. Its aim is to
present an up-to-date review of the status of our knowledge in this field of materials
science and technology. As such it is the first comprehensive single book on this new
area of materials science. Since no field in material science today can be adequately
covered in a current review by one individual, because of the diversity of talents
brought to bear on the subject, this book is composed of a large set of carefully selected
contributions from individual authors. Each chapter is written by an author who was
selected from the world-wide pool of researchers as one of the outstanding contributors
to the particular subject area in amorphous alloys. The attempt was made, and I believe
successfully, to cover the entire field for these amorphous alloys. There are chapters on
the history, on the fundamentals of formation, on sample preparation, on structure, on
crystallization and on the unique physical, magnetic, electronic, chemical and thermal
properties as well as the applications and potential applications. Each chapter has a
lengthy list of references for those readers interested in more details. It is hoped that the
lengthy combined subject index will be a useful appendix.
I have to thank many people, and I take pleasure in doing so. First, I must thank
each of the authors of the chapters for adhering to the schedule set forth, which renders
the information up to date. Thanks are also due to the publisher, Butterworths, for
their great co-operation in all aspects of producing this book and, in particular, also for
their adherence to a tight schedule so that this book was published promptly. I also
acknowledge the inputs of my many colleagues working on amorphous metals at the
General Electric Corporate Research and Development for their advice in the planning
of this book. I am also extremely grateful to the General Electric Corporate Research
and Development for providing the secretarial help and in particular to Cheryl
Santomartino for collating the subject index from the individual chapter indices
provided by each author. Finally, I am indebted to my wife for her many suggestions
and for her interest in this book.
F. E. Luborsky
Schenectady
List of contributors
R. W. Cahn H.-J. Güntherodt
Laboratoire de Métallurgie Physique, Université Institut für Physik, Universität Basil, CH-4056
de Paris-Sud, Centre D'Orsay, Bâtiment 413, Basil, Switzerland
91405 Orsay Cedex, France
K. Hashimoto
B. Cantor
The Research Institute for Iron, Steel and Other
Dept. of Metallurgy and Science of Materials,
Metals, Tohoku University, 1-1, Katahira-2
University of Oxford, Parks Road, Oxford, OX1
Chôme, Sendai, Japan
3PH, England
H. S. Chen H. Kronmüller
Materials Research Physics Department, Bell Max Planck Institute für Metallforschung,
Telephone Laboratories, Murray Hill, NJ 07974, Institut für Physik, 7000 Stuttgart 80,
USA Heisenbergstr. 1, FDR
H. A. Davies H. Kumura
Dept. of Metallurgy, The University of Sheffield, The Research Institute for Iron, Steel and Other
Sheffield SI 3JD, England Metals, Tohoku University, 1-1, Katahira-2
Chôme, Sendai, Japan
T. Egami
Dept. of Metallurgy and Materials Science, Kl,
H. H. Leibermann
University of Pennsylvania, Philadelphia, PA
Allied Corporate Technology, MetGlas
19174, USA
Building, 6 Eastmans Rd., Parsippany, NJ
J. L. Finney 07054, USA
Dept. of Crystallography, Birkbeck College,
Malet Street, London, WC1E 7HX, England F. E. Luborsky
General Electric Company, Corporate Research
H. Fujimori and Development, Building K-l, Room 1C36,
The Research Institute for Iron, Steel and Other Schenectady, NY 12301, USA
Metals, Tohoku University, 1-1, Katahira-2
Chôme, Sendai, Japan
T. Masumoto
K. Fukamichi The Research Institute for Iron, Steel and Other
The Research Institute for Iron, Steel and Other Metals, Tohoku University, 1-1, Katahira-2
Metals, Tohoku University, 1-1, Katahira-2 Chôme, Sendai, Japan
Chôme, Sendai, Japan
R. P. Messmer
C. F. Hague General Electric Company, Corporate Research
Institut für Physik, Universität Basil, CH-4056 and Development, Building K-l, Room 2A30,
Basil, Switzerland Schenectady, NY 12301, USA
List of contributors vn
S. A. Miller M. Scott
General Electric Company, Corporate Research Standard Telecommunication Laboratories,
and Development, Building K-l, Room 267MB, Ltd., Optical Waveguides Division, London
Schenectady, NY 12301, USA Road, Harlow, Essex, CM 17 9NA, England
N. Moser C. H. Smith
Max Planck Institute für Metallforschung,
Allied Corporation, Materials Research Center,
Institut für Physik, 7000 Stuttgart 80,
Box 1021R, Morristown, NJ 07960, USA
Heisenbergstr. 1, FDR
P. Oelhafen F. Spaepen
Institut für Physik, Universität Basil, CH-4056 Division of Engineering and Applied Physics,
Basil, Switzerland Harvard University, Cambridge, MA 02138,
USA
R. C. O'Handley
Dept. Materials Science and Engineering, K. Suzuki
Building 13, Room 5065, MIT, Research Institute for Iron, Steel and Other
77 Massachusetts Ave., Cambridge, MA 02139, Metals, Tohoku University, 1-1, Katahira-2
USA Chôme, Sendai, Japan
D. G. Onn
A. I. Taub
223 Sharp Laboratory, Dept. of Physics, College
General Electric Company, Corporate Research
of Arts and Science, University of Delaware,
and Development, Building K-l, Room 267MB
Newark, DE 19711, USA
Schenectady, NY 12301, USA
S. J. Poon
C. N. J. Wagner
Dept. of Physics, McCormack Rd., University of
Virginia, Charlottes ville, VA 22901, USA Dept. of Materials Science and Engineering,
School of Engineering and Applied Science,
University of California, Los Angeles, CA
K. V. Rao
90024, USA
Central Research Laboratory, M MM Company,
P.O. Box 33221, St. Paul, MN 55133, USA
E. P. Wohlfarth
D. Raskin Dept. of Mathematics, Imperial College of
Allied Corporation, Materials Research Center, Science and Technology, Queen's Gate, London
Box 1021R, Morristown, NJ 07960, USA SW7 2BZ, England
Chapter 1
Amorphous metallic alloys
F. E. Luborsky
General Electric Company, Schenectady, New York, USA
1.1 Introduction
Amorphous metallic alloys are metals and metal alloys with no long range atomic
order. They have also been called glassy alloys or non-crystalline alloys. They are made
by a variety of techniques all of which involve the rapid solidification of the alloying
constituents from the gas or liquid phases. The solidification occurs so rapidly that the
atoms are frozen in their liquid configuration. There are clear structural indications and
indications from their various properties that nearest neighbour, or local, order does
exist in most amorphous metallic alloys, but no long range atomic order.
There are unique magnetic, mechanical, electrical and corrosion behaviours which
results from this amorphous structure. For example, they behave as very soft magnetic
materials, in fact magnetic losses in high magnetization alloys have been measured
which are lower than those measured in any other known crystalline alloys; they are
exceptionally hard and have extremely high tensile strengths and in some alloys the
coefficient of the thermal expansion can be made to be zero; they have electrical
resistivities which are three to four times higher than those of conventional iron or
iron-nickel alloys; and finally some of the amorphous alloys are exceptionally
corrosion resistant.
There are two or possibly three technologically important classes of magnetic
amorphous alloy; the transition metal-metalloid (TM-M) alloys, the rare
earth-transition metal (RE-TM) alloys and possibly the transition metal-zirconium or
hafnium alloys. The TM-M alloys typically contain about 80 atom per cent iron, cobalt
or nickel with the remainder being boron, carbon, silicon, phosphorus or aluminium
and are typically prepared by rapid quenching from the melt, although other techniques
such as sputtering, electrodeposition and chemical deposition have been used. The
presence of the metalloids is necessary to lower the melting point making it possible to
quench the alloy through its glass temperature rapidly enough to form the amorphous
phase. Once made the same metalloids stabilize the amorphous phase but their presence
drastically alters the magnetic, mechanical and electrical properties of the alloy by
donating electrons to the J-band. The presumed isotropic character of the TM-M
amorphous alloys had been predicted to result in very low coercivities and hysteresis
loss and high permeabilities; all the properties of technological significance for
application as soft magnetic materials. These good properties have been achieved in
1
2 Amorphous metallic alloys
some melt-quenched alloys and we can account for their behaviour by the same models
as used for conventional crystalline soft magnetic materials. The same statements can
be made for the recently reported TM-Zr-Hf alloys. These normally contain about 10
atom per cent zirconium or hafnium but the addition of even a few percent of boron
greatly enlarges the amorphous forming region. Because they have properties which are
very similar to the TM-M alloys it is expected that they will be used in similar devices.
The RE-TM alloys, however, are normally prepared by sputter deposition and
have properties especially suited to bubble memory devices, for example, low saturation
magnetization and high anisotropy perpendicular to the plane. These types of
amorphous alloy will not be discussed in any detail in this monograph.
Amorphous alloys have been shown to have vastly superior magnetic properties
for application in large transformers and to have a combination of mechanical and
magnetic properties that makes them extremely likely candidates for application in
recording heads, in some electronic size transformers and in various types of sensor.
Thus, the application of amorphous alloys in various magnetic devices appears to be
assured. Nickel-based amorphous alloys for brazing foil have also been in use for
several years. This technique provides all-metallic brazing foils with no binders,
resulting in greater strength and greater assembly precision in reduced time. Many
other applications have been reported in the technical literature but none has appeared
on the market yet.
Until recently the major efforts in solid state physics have been confined to
understanding the properties of crystalline solids. Microscopic information has been
obtained from studies of the properties of single crystals. Amorphous solids now
represent a new state of matter. Some of their properties are entirely as predicted. Other
properties have unexpected features and ambiguities. For example, although amorph-
ous solids consist largely of random aggregates of atoms their densities are only slightly
different from the density of crystals of the same composition.
The broad theoretical question is: how does the amorphous atomic structure
affect all of the characteristics, e.g. magnetic, mechanical, chemical or corrosion, and
electrical. Each of these will be discussed in some detail in the forthcoming sections of
this review. Much of our understanding has come from comparing the properties of the
amorphous alloy with the same or a similar crystalline alloy. However, this has only
limited applicability because most of the interesting amorphous alloys have no simple
or single crystalline counterpart. One of the singular advantages of studies on
amorphous alloys is that we can vary the composition continuously, to prepare
homogenous alloys which can be studied as a function of composition and temperature
without complicating interference from structural phase transitions. Although these
complications do not exist, more subtle changes do occur at temperatures well below
crystallization. For example, phase separation, diffusion of various species and
structural relaxations all occur even though the alloy remains amorphous. That is, the
amorphous phase is not a stable ground state of the solid. All of these changes can have
effects on the observed properties.
The purpose of this book is to document these unique characteristics and the
applications they lead to and to discuss the present status of our basic understanding of
the origins of their unique behaviour. Most of the emphasis will be on melt-quenched
transition metal-metalloid and transition metal-zirconium type alloys.
1.2 Historical development of amorphous metallic alloys
In the past 8000 years that humans have used metals their structure has consisted
of crystalline aggregates. Historically, the first report in which a range of amorphous,
Amorphous metallic alloys 3
i.e. non-crystalline, metallic alloys were claimed to have been made was by Kramer1,2.
This was based on vapour deposition. Somewhat later Brenner et al.3 claimed to have
made amorphous metallic alloys by electrodepositing nickel-phosphorus alloys. They
observed only one broad diffuse peak in the X-ray scattering pattern in the non-
magnetic high-phosphorus alloys. Such alloys have been in use for many years as hard,
wear and corrosion resistant, coatings. It was not until 1960 that Duwez and his
coworkers discovered a method of preparing amorphous alloys by direct quenching
from the melt. The story of this discovery is a fascinating one and has been told by
Duwez4. An edited version follows.
Metallurgists are very familiar with the term 'quenching'. This is generally defined
as the process of rapid cooling. The main purpose of quenching is to cool an alloy at a
high enough rate so that phases stable at high temperatures are either partially retained,
transformed into non-equilibrium phases, or both. Subsequent heat treatment is then
used to control the relative amounts as well as the microstructure of the desired phases
to achieve the optimum physical properties of the final product. In this definition of
quenching nothing is said about the initial state of the material to be quenched,
although it is taken for granted that it is in the solid state. This need not be the case and
high cooling rates can indeed be applied to alloys in the liquid state as well.
In quenching solid alloys, the purpose is to cross the phase boundaries rapidly
enough to prevent totally, or at least partially, the equilibrium reactions from taking
place. In quenching from the liquid state the critical phase boundaries are the liquidus
and the solidus in the phase diagram. Since the atomic mobility in a liquid is far greater
than in a solid, the rates of cooling required to influence the crystallization of an alloy
are obviously much greater than those necessary to prevent a phase change in the solid
state. As a result, the conventional techniques of quenching a solid do not lead to any
significant results when applied to a liquid alloy. Very simple techniques based on
cooling by conduction of the liquid on to a solid substrate have been developed and
crystallization of liquid alloys can definitely be modified and in some cases completely
suppressed.
The motivation for achieving extreme rates of cooling in liquid alloys was to try to
prevent the separation into two phases in binary alloy systems in which, according to
the generally accepted Hume-Rothery rules, the two metals should form a complete
series of solid solutions, and yet a eutectic system is found under equilibrium
conditions. The test case chosen for evaluating the efficiency of the quenching
techniques was the copper-silver system, and in September 1959 a complete series of
solid solutions in this system was obtained at Caltech. At that time, the rate of
quenching was not known, and no time was devoted to try to measure it, because more
exciting results immediately followed. These unexpected results were the synthesis of a
new crystalline non-equilibrium phase in the silver-germanium system which under
equilibrium conditions is of the simple eutectic type. Shortly after that, the ultimate
goal in quenching from the liquid state was reached when a non-crystalline
(amorphous) structure was obtained in gold-silicon alloys. Total suppression of the
crystallization process during solidification had been achieved.
Almost simultaneously Miroshnichenko and Salli5 in the USSR reported on a
very similar device for preparing amorphous alloys. In this technique a liquid metal
alloy drop is propelled on to a cold surface where it spreads into a thin film and is thus
rapidly solidified. Duwez actually propelled the liquid drop, whereas Miroshnichenko
and Salli propelled two opposing pistons together with the drop in between. These
techniques soon acquired, over the opposition of its inventor, the anomatopaeic
designation of 'splat-cooling'. These splat-cooling techniques can generate cooling rates
of greater than a million degrees per second, thus creating a completely new metallurgy
4 Amorphous metallic alloys
of highly supersaturated solid solutions, new metastable crystalline structures and
glassy alloys.
The final development in the story of the preparation of amorphous alloys was the
publication by Pond and Maddin6 of a technique for the preparation of continuous
long lengths of ribbons. This opened up the possibility of large scale production and set
the stage for the explosive growth of work on amorphous alloys since it was now clear
that these alloys could be prepared in large quantities at low cost. Although large
quantities, relative to the usual laboratory quantities of a few grams per run, are now
available commercially, the price is still dropping rapidly (Figure 1.1). The ultimate cost
-METALLIC GLASSES
(Fe AND FeNi)
Figure 1.1 Past prices and future possible
prices of metallic glasses and some competitive
0.1 mm materials. Solid dots are prices and price
3% SiFe ranges from Allied Chemical for METGLAS for
0.3 mm -,-r-r-^v"" different alloys, widths and quantities. The open
circles are estimates from USA experts. The fine
1975 1980 1985 1990 cross-hatched line is the prognosis from
YEAR Vacuumschmelze (after Raskin and Davis7)
(or price) has been estimated for very large quantity production to be potentially as
small as 2.00 dollars/kg for the iron-boron based alloys. Thus, these alloys may become
cost competitive with the oriented Fe-3.2%Si which sells for about 1.30—
1.50 dollars/kg. Concurrent with the drop in price the production quantity has been
projected by Raskin and Davis7 to rise from the present level of roughly 15 000 kg to
400000 kg by 1985 and to 40000000 kg by 1987 (Figure 1.2). This inverse relation
between price and quantity used appears to be valid for many materials and is
illustrated in Figure 1.3 for a variety of soft magnetic materials.
The other part of this fascinating story has to do with the ferromagnetic
properties of amorphous metallic alloys. Because of the lack of atomic ordering it was
believed for many years that ferromagnetism could not exist in amorphous solids.
However, in 1960 Gubanov8 predicted, on the basis of theoretical analysis, that
amorphous solids would be ferromagnetic. This was based on evidence that the
electronic band structure of crystalline solids did not change in any fundamental way
on transition to the liquid state. This implies that the band structure is more dependent
on short-range, rather than long-range, order so that ferromagnetism, which depends
on short-range order, should not be destroyed in the corresponding amorphous solid.
The theoretically expected retention of ferromagnetic behaviour in amorphous solids
was first demonstrated by Mader and Nowick9 in 1965 in work on vacuum-deposited
Co-Au alloys and soon thereafter by Tsuei and Duwez10 in work on splat-cooled
Pd-20 atom % Si containing some ferromagnetic element partially substituted for the
palladium. The first alloy with a substantial magnetization, further confirming