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E Materials Research and Engineering Edited by B. llschner and K. C. Russell Horst Buhl (Ed.) Advanced Aerospace Materials Springer-Verlag Berlin Heidelberg New York London Paris Tokyo HongKong Barcelona Budapest Dr. HORST BUHL DLR, German Aerospace Research Establishment Institute of Materials Research Linder Hohe W-5000 KOin 90/Germany Series Editors Prof. BERNHARD ILSCHNER Poly technique Federale de Lausanne Laboratoire de Metallurgie Mecanique MX-D Ecublens Ecole CH-I0l5 Lausanne/Switzerland Prof. KENNETH C. RUSSELL Department of Materials Science and Engineering and Department of Nuclear Engineering Room 8-411 Massachusetts Institute ofT echnology Cambridge, MA 02139/USA ISBN 978-3-642-50161-6 ISBN 978-3-642-50159-3 (eBook) DOl 10.1007/978-3-642-50159-3 Library of Congress Cataloging-in-Publication Data Buhl, Horst Advanced aerospace materials 1 Horst Buh!. (Materials researches and engineering) Includes bibliographical references and index. ISBN 978-3-642-50161-6 I. Airplanes --Materials. 2. Composite materials. I. Title. II. Series: Materials research and engineering (Unnumbered) TL698.B84 1992 629.1--dc20 92-30704 This work is subject to copyrighLAll rights are reserved, whether the whole orpart ofthe material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms orin otherways,and storage in data banks. Duplication ofthis publication orparts thereofis only permitted under the provisions ofthe German Copyright Law ofSeptember9, 1965, in its current version and a copyright fee must always be paid. Violations fall under the prosecution act of the German Copyright Law. © Springer-Verlag Berlin, Heidelberg 1992 Softcover reprint of the hardcover 1st edition 1992 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence ofa specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Camera ready by author 61/3020-543210 - Printed on acid-free paper. DlR - Institut fur Werkstoff-Forschung Arbe tsschwerpunkte • hochfeste lelchlbauwerkstofle lOr Lu!t und Raumlahn • Hochtemperatur Werks!ofle lOr Antflebe Werkstofte Akuvlt&ten Professor Dr. Wolfgang J. G. Bunk Professor Dr. W.G.J. Bunk, Director of the DLR (German Aerospace Research Establishment) Institute of Materials Research since 1970, retires in 1992. With his retirement an epoch of the institute's history comes to an end, an epoch characterized by expansion in resources, competence, and size, and national as well as international appreci ation. As an expression of their gratitude for his leadership, the scientific staff of the institute devotes this book to Professor Bunk. On beha(f of the members of the staff Horst Buhl Foreword Very light, very strong. extremely reliable - aircraft and aerospace engineers are. and have to be. very demanding partners in the materials community. The results of their research and development work is not only crucial for one special area of applications. but can also lead the way to new solutions in many other areas of advanced technology. Springer-Verlag and the undersigned editor are pleased to present in this volume. an overview of the many facets of materials science and technology which have been the objective of intensive and systematic research work during past decades in the laboratories of the German Aerospace Research Establishment. Its contents shows clearly the interrelations between goals defined by the user. fundamentals provided by the scientists and viable solutions developed by the practical engineer. The particular personal touch which has been given to this volume by its authors in dedicating it as a farewell present to Professor Wolfgang Bunk. inspiring sci entist and director of the DLR Intitute of Materials Research for more than 20 years. has obviously given an added value to this important publication. Surely. this truly cooperative endeavour will render a valuable service to a large interna tional community of interested readers. many of them having personal links to the Institute. its director and its staff. Lausanne. June 1992 Bernhard I1schner Preface During the period 1970 to 1992 the European aircraft industry experienced a big impetus and a worldwide breakthrough with the successful implementation of the family of Airbus aircraft. In the area of space launch vehicles. Ariane developed into an efficient and reliable carrier for satellites. Safe. reliable and durable materials were the precondition for this success in both cases. Columbus. the European contribution to the US space station Freedom. as well as the European efforts to create an autonomous space policy regarding such projects as Hermes and Sanger, are a big challenge for the materials research community. too. The authors of this book. my collegues at the Institute of Materials Research of the German Aerospace Research Establishment. took part in this development from the beginning. The emphasis of this book. therefore. lies on the research activities of these authors. It is primarily conceived as a vista into the fascinating world of aerospace materials and may well serve as an introduction. On the other hand, its content is always embedded into the context of the international state of knowledge in materials science, and many topics are dealt with in detail, limited however by space considerations. A comprehensive bibliography yields access to the many specialized fields of aerospace materials. The book is introduced by a visionary overview by W.J.G. Bunk on the present situation of aerospace materials and perspectives for the future. Thus. the ground is prepared to allow the reader to examine different aspects of the subject matter. The structure of the content is, as in many treatments of materials science and engineering, developed along two axes: First, groups of materials like metals, ceramics, polymers, and their composites are dealt with. Then properties as well as suitable test methods and the application related interpretation of test results form a second guideline. This holds for mechanical properties such as fracture and fatigue behaviour as well as for corrosion resistance and the field of microstruc tural and microanalytical techniques. After all, the goal is a cost effective and reliable aerospace structure, and these properties do not exclusively relate to one single material. The book is designed as an introduction to materials research as well as a guide to anyone who comes in contact with advanced materials. It may be an introduc tion for graduate students of engineering science into the field of highly developed lightweight structural and high temperature turbine materials. The comprehensive survey may also supply materials scientists with information on the actual state of the art. new materials and test methods and quick answers to problems. as well as references to more profound information. Also, service engineers, not only from the aerospace industry, may find valuable details and references. VIII Preface I am greatly indebted to my colleages at the Institute of Materials Research, who contributed to this book and who are listed below: Braue, W. Braun, R. Bunk, W.GJ. Doker, H. Dudek, H.-J. Eschweiler, J. Fritscher, K. Goring, J. Kumpfert, J. Lehnert, F. Leucht, R. Marci, G. Nowack, H.I) Peters, M. Peters, P.W.M. Pleger, R. Ratzer-Scheibe, H.-J. Saruhan, B. Schneider, H. Schulte, K.2) Schulz, U. Spiegelberg, M. Staniek, G. Trautmann, K.-H. Ward, C.H.3) Welpmann, K. I) now Universitat Gesamthochschule Duisburg 2) now Technische Universitat Hamburg-Harburg 3) now Wright Laboratory, Wright-Patterson AFB, OH, USA The support of Prof. B. Ilschner, the editor of the Springer Series, "Materials Research and Development", is gratefully acknowledged. He enabled the publica tion of this book and supported its preparation with much valuable advice. Special thanks owe given to Mrs. C. Kotauschek who typed most of the contributions and to Mrs. S. Giegerich who revised the text regarding the language. Thanks is due also to the following technical collaborators who were involved in the preparation of the numerous figures and diagrams: M. Alperth, K. Baumann, H. Hemmnns, U. Krebber, H. Mettemich, and H. Schurmann. Cologne, June 1992 Horst Buhl Contents 1. Situation and Perspectives .................................. 1 2. Metallic Materials and Metal Matrix Composites .................. 21 2.1 Metallic Materials .................................... 21 2.l.l Aluminium Alloys .................................. 21 2.1.1.1 High-Strength Aluminium Alloys ..................... 21 2.1.1.2 Aluminium-Lithium Alloys ......................... 35 2.1.1.3 Powder Metallurgy of Aluminium Alloys ............... 47 2.1.2 Titanium Alloys and Aluminides ........................ 58 2.1.2.1 Titanium Alloys ................................. 58 2.1.2.2 Titanium Aluminides ............................. 73 2.1.3 Superalloys and Coatings ............................. 84 2.1.3.1 S uperalloys .................................... 84 2.1.3.2 High Temperature Corrosion ........................ 87 2.1.3.3 Coatings ...................................... 96 2.2 Metal-Matrix Composites ............................. 108 2.2.1 Metal-Matrix Composites with Aluminium Matrix ........... 108 2.2.2 Fibre Reinforced Aluminium Laminates .................. 118 2.2.3 Titanium Matrix Composites .......................... 124 2.2.4 Interfaces in Metal Matrix Composites ................... 139 3. Ceramic Materials and Ceramic Matrix Composites ............... 153 3.1 Non-Oxide Materials (Silicon Nitride) ..................... 153 3.1.1 Fabrication and Microstructural Development of Non-Oxide Ceramics (Silicon Nitride) ............................ 154 3.1.2 Silicon Nitride Matrix Composites ...................... 164 3.1.3 Fracture and Fatigue of Non-Oxide Ceramics .............. 177 3.2 Oxide Materials (Mullite) ............................. 189 3.3 Imaging Microstructures of Monolithic Carbons and Carbon/Carbon Composites in the TEM .............................. 203 4. Polymer Matrix Composites ............................... 219 4.1 Quasi-Static Strength of Polymer Matrix Composites .......... 220 4.2 Fatigue Strength of Polymer Matrix Composites .............. 238 5. Materials Characterization and Life Prediction 246 5.1 Microstructural and Microanalytic Methods ................. 246 5.2 Fatigue and Fracture of Metallic Materials .................. 263 5.2.1 Random Load Fatigue and Life Prediction ................ 263 5.2.2 Physical Reasons for the Existence of L\Kcff ................ 273 5.2.3 Crack Growth Life Prediction ......................... 289 5.3 Special Testing Techniques ............................ 296 x Contents 5.3.1 Stress Corrosion Testing ............................. 296 5.3.2 Biaxial Testing ................................... 308 5.3.3 Chevron Notched Specimen Testing ..................... 318 Bibliography 327 Abbreviations 360 Index ................................................. 363 Laudatio ............................................... 372 1. Aerospace Materials, Situation and Perspectives W.J.G. Bunk Since aluminium was first used about 1900 as a structural material for the Zeppelin, this light metal was further developed into a long list of alloys and properties tailored to fit the needs of aeroplane builders around the world. It seems to have come to a market saturation because of the advent of carbon fibre rein forced polymer matrix composites. Titanium and nickel base super alloys dominate compressor and turbine materials for jet engines. Intermetallics and ceramics may replace some alloys in the future. From nature engineers have learned to strengthen a component by particle or fibre reinforcement. Quite a number of innovative processing techniques emerging from aerospace material targets have been designed and introduced. It is not surprising to recog nize materials research and development efforts shifting to some extent from conventional materials processing companies to more or less integrated aerospace groups. This may even be more pronounced in the future for quality, safety and cost reasons. Transfer of advanced aerospace materials and processing technolo gies to other markets is possible and often wanted, but sometimes problematic from the economic point of view. It takes 10 years or more until a new material produced with advanced process ing technology reaches maturity and full commercialization. This fact is sometimes difficult to acknowledge by industrial management and governmental funding agencies. Strategic considerations lead to goals, requirements and limitations. Safety comes first, followed by performance, and final\y cost of material and processing net shapes, including recycling: A system's approach. One notices considerable competition between light metals and carbon fibre reinforced polymers (PMC). There are different extrapolation curves published in the literature concerning the balance of light metals and PMCs in airframe com ponents. One of the important requirements for aerospace materials is resistance to ele vated temperatures. Figure 1.1 summarizes the experience of the aerospace industry. For aerospace materials and components considerable development activity is required in order to correctly select and ratify their suitability. It is necessary to demonstrate performance achievement and acceptable manufacturing costs. Influ encing factors include environmental conditions, ease of processing and ability to inspect and repair parts, to name just a few.