ADVANCED STRUCTURAL MATERIALS
INTRODUCTION TO ADVANCED MATERIALS CHAPTER SMALL SCALE CONTACT AND ADHESION IN NANO- AND BIO-SYSTEMS MECHANICAL CHARACTERIZATION OF THIN FILM MATERIALS FOR MEMS DEVICES SILICON-BASED MICROELECTROMECHANICAL SYSTEMS (SI-MEMS) POROUS METALLIC MATERIALS A THERMODYNAMIC OVERVIEW OF GLASS FORMATION ABILITIES: APPLICATION TO AL-BASED ALLOYS NITI-BASED HIGH-TEMPERATURE SHAPE-MEMORY ALLOYS: PROPERTIES, PROSPECTS, AND POTENTIAL APPLICATIONS COBALT ALLOYS AND COMPOSITES THE SCIENCE, TECHNOLOGY, AND APPLICATIONS OF ALUMINUM AND ALUMINUM ALLOYS METAL MATRIX COMPOSITES: TYPES, REINFORCEMENT, PROCESSING, PROPERTIES AND APPLICATIONS TITANIUM ALLOYS: STRUCTURE, PROPERTIES, AND APPLICATIONS NIOBIUM ALLOYS AND COMPOSITES MO-SI-B ALLOYS FOR ULTRAHIGH TEMPERATURE APPLICATIONS NICKEL-BASE ALLOYS INTRODUCTION APPLICATIONS OF ADVANCED MATERIALS MATERIALS IN AEROENGINES MATERIALS FOR THE NATIONAL AEROSPACE PLANE MATERIALS IN SPORTING GOODS MATERIALS FOR HUMAN PROSTHETIC DEVICES MATERIALS FOR AUTOMOTIVE APPLICATIONS ENGINEERING OF BALANCED PROPERTIES SUMMARY REFERENCES INTRODUCTION ADVANCED STRUCTURAL METALLIC MATERIALS HAVE HAD A CONSIDERABLE IMPACT ON THE DEVELOPMENT OF A WIDE RANGE OF STRATEGIC TECHNOLOGIES HOWEVER, ONLY A FEW SPECIALISTS ARE AWARE OF THE BASIC SCIENTI?C CONCEPTS THAT HAVE GUIDED THE DESIGN OF NEW ALLOYS, INTERMETALLICS, AND METAL MATRIX COMPOSITES THESE CONCEPTS ARE DESCRIBED IN THIS BOOK IN AN EFFORT TO MAKE SUCH KNOWLEDGE WIDELY ACCESSIBLE TO ENGINEERS AND SCIENTISTS WHO HAVE A STRONG TENDENCY TO BECOME RATHER FOCUSED ON A FEW PARTICULAR SYSTEMS WE ALSO HOPE THAT THE BOOK WILL SERVE AS A USEFUL OVERVIEW TO THE PUBLIC AT LARGE WHO HAVE FAITH IN THESE ADVANCED MATERIALS WITHOUT KNOWING MUCH ABOUT THE PROPERTIES THAT MAKE THEM SUITABLE FOR STRUCTURAL APPLICATIONS WE HOPE THAT THIS BOOK WILL PROVIDE A SIMPLE PICTURE OF THE BASIC CONCEPTS THAT GUIDE THE DEVELOPMENT OF NEW ALLOYS AND COMPOSITE MATERIALS FOR THIS REASON, EXCESSIVE DETAIL HAS BEEN AVOIDED IN THE INDIVIDUAL SECTIONS IN AN EFFORT TO RETAIN CLARITY IN THE PRESENTATION OF KEY IDEAS HOWEVER, THE MORE INQUIRING READER IS PROVIDED WITH AN EXTENSIVE LIST OF REFERENCES AT THE END OF EACH CHAPTER FINALLY, IT IS IMPORTANT TO EMPHASIZE THAT THIS BOOK IS NOT INTENDED TO BE A COMPREHENSIVE OVERVIEW OF ADVANCED METALLIC MATERIALS NO AUTHORS COULD POSSIBLY PROVIDE A COMPLETE REVIEW OF ALL THE RELEVANT MATERIAL AVAILABLE IN THE LITERATURE INSTEAD, WE HOPE THAT THIS TEXT WILL PROVIDE A USEFUL PICTURE OF THE BASIC IDEAS USED TO CONTROL THE FRACTURE PROPERTIES OF ENGINEERED STRUCTURAL MATERIALS IN AEROENGINES OUR ABILITY TO POWER MODERN AIRPLANES DEPENDS LARGELY ON THE THRUSTS GENERATED BY AEROENGINES SINCE SPEED AND SAFETY ARE CRITICAL IN BOTH COMMERCIAL AND MILITARY AIRCRAFTS, THE SELECTION OF MATERIALS FOR AEROENGINE APPLICATIONS REQUIRES A CAREFUL BALANCE OF PERFORMANCE AND RISK [3] MATERIAL COST IS ALSO AN IMPORTANT FACTOR, ESPECIALLY IN COMMERCIAL AEROENGINES WHERE PLANE CRASHES CAN ATTRACT GLOBAL ATTENTION, PARTICULARLY IN CASES WHERE HUMAN LIVES ARE LOST ADVANCED STRUCTURAL MATERIALS MATERIALS IN MODERN DAY AEROENGINES ARE, THEREFORE, INTRODUCED ONLY AFTER EXTENSIVE MATERIALS DEVELOPMENT AND TESTING HAVE BEEN PERFORMED OVER A PERIOD OF W15 YEARS THIS HAS LED TO UNPRE- CEDENTED LEVELS OF SAFETY AND PERFORMANCE IN MOST OF THE AEROENGINES THAT ARE CURRENTLY IN SERVICE A SCHEMATIC OF A MODERN DAY AEROENGINE IS PRESENTED IN FIGURE 1 2 THIS SHOWS THE THREE MAIN SECTIONS OF THE ENGINE, I E , THE FAN, COMPRESSOR, AND TURBINE AIR IS SUCKED IN BY THE FAN, WHICH IS NORMALLY FABRICATED FROM A TITANIUM ALLOY (SUCH AS TI–6AL–4V) OR A POLYMER MATRIX COMPOSITE THE AIR IS THEN PASSED THROUGH MULTIPLE STAGES OF THE COMPRESSOR, WHICH CONSISTS PRIMARILY OF DISKS AND BLADES THAT ARE ALSO FABRICATED PRIMARILY FROM TITANIUM ALLOYS SUCH AS TI–6AL–4V THE TEMPERATURES IN THE FAN AND AEROENGINE SECTIONS OF THE AEROENGINE ARE RELATIVELY LOW (CLOSE TO ROOM TEMPERATURE) HOWEVER, HIGHER TEMPERATURES (W4008C–5008C) MAY OCCUR IN THE HIGH-PRESSURE STAGES BEYOND THE COMPRESSOR, THE AIR IS IGNITED IN A COMBUSTOR, BEFORE EXPANDING THROUGH MULTIPLE STAGES OF THE TURBINE AND THE NOZZLES AT THE BACK END OF THE ENGINE NICKEL AND COBALT-BASED SUPERALLOYS ARE OFTEN USED IN THE COMBUSTOR AND TURBINE SECTIONS OF THE AEROENGINE DUE TO HIGH TEMPERATURES EXPERIENCED IN THESE SYSTEMS (FROM W5008C TO 6508C IN THE DISKS TO W12008C AT THE TIPS OF THE BLADES IN THE TURBINES) THE COMPOSITIONS AND MICROSTRUCTURES OF THE SUPERALLOYS ARE ALSO TAILORED TO PROVIDE THE REQUIRED COMBINATIONS OF STRENGTH, CREEP, FATIGUE, AND OXIDATION RESISTANCE REQUIRED FOR SERVICE IN AEROENGINES THAT REVOLVE AT ANGULAR SPEEDS AS HIGH AS 20,000 REVS/MINUTE BEYOND THE TURBINE SECTION OF THE AEROENGINE, AIR IS EXPANDED THROUGH NOZZLES THAT ARE TYPICALLY FABRICATED FROM COATED NIOBIUM-BASED ALLOYS (FIGURE 1 3) THE ABOVE MATERIALS SYSTEMS HAVE BEEN LARGELY OPTIMIZED BY EMPIRICAL PROCESSING AND ALLOY DESIGN SCHEMES HOWEVER, MANY OF THE SYSTEMS HAVE INHERENT LIMITS IN PROPERTIES THAT MAY NOT BE OVERCOME BY ALLOYING AND HEAT TREATMENT FOR EXAMPLE, THE DENSITIES AND MODULI OF METALLIC MATERIALS MAY NOT BE ALTERED SIGNI?CANTLY BY ALLOYING HENCE, NEW MATERIALS ARE OFTEN NEEDED TO EXCEED THE INTRINSIC LIMITS OF THE EXISTING STRUCTURAL METALLIC SYSTEMS IN MODERN AEROENGINES [3–6] THE EMERGING SYSTEMS THAT HAVE BEEN IDENTI?ED AS POTENTIAL CANDIDATES TO REPLACE EXISTING AERO- ENGINE MATERIALS ARE LISTED IN TABLE 1 1, ALONG WITH EXISTING AEROENGINE MATERIALS NOTE THAT THESE EVOLUTION OF ENGINEERING MATERIALS 10 000BC 5000BC 1000 1500 10 000BC 5000BC GOLD COPPER BRONZE IRON CAST IRON STEELS ALLOY METALS METALS STEELS LIGHT ALLOYS SUPER ALLOYS ALLOYS TILANIUM ZIRCONIUM ETC GLASSY METALS DEVELOPMENT SLOW: MOSTLY QUALITY CONTROL AND PROCESSING AL-LITHIUM ALLOYS DUAL PHASE STEELS MICROALLOYED STEELS NEW SUPER ALLOYS POLYMERS COMPOSITES CERAMICS POLYMERS COMPOSITES CERAMICS METAL-MATRIX COPOSITES KELVAR-FRP CFRP GERP CERAMICS COMPOSITES TOUGH ENGINEERING CONDUCTING POLYMERS HIGH TEMPERATURE POLYMERS HIGH MODULUS POLYMERS POLYESTERS EPOXIES ACRYLICS PP PS PC PE PMMA BAKELITE RUBBER YEAR NYLON GULES STONE FLINT POTTERY GLASS CEMENT REFRACTORIES PORTLAND CEMENT FUSED SILICA CERMETS PYRO- CERAMICS RELATIVE IMPORTANCE RELATIVE IMPORTANCE WOOD SKINS FIBERS CERAMICS STRAW-BRICK PAPER (AL2O3, SI3N4, PSZ, ETC ) FIGURE 1 1 EVOLUTION OF THE HISTORICAL EVOLUTION OF THE RELATIVE IMPORTANCE OF THE DIFFERENT CLASSES OF MATERIALS ADVANCED STRUCTURAL MATERIALS MATERIALS FOR THE NATIONAL AEROSPACE PLANE THE NATIONAL AEROSPACE PLANE (NASP) VEHICLE WAS CONCEIVED IN THE 1980S IN THE U S IT WAS PROPOSED AS A MACH-10 HYPERSONIC VEHICLE THAT COULD TRAVEL FROM TOKYO TO NEW YORK IN TWO HOURS [9] AS WITH MATERIAL SURFACE TEMPERATURE, °F APPROXIMATE YEAR OF USE IN ENGINE CARBON/CARBON COMPOSITES CERAMIC MATRIX COMPOSITES & CERAMICS THERMAL-BARRIER COATINGS CONVENTIONALLY CAST FIBER-REINFORCED SUPERALLOYS ODS SUPERALLOYS EUTECTICS SINGLE CRYSTALS DIRECTIONALLY SOLIDIFIED SUPERALLOYS AIR INTAKE COMPRESSION COMBUSTION EXHAUST CONTINUOUS FIGURE 1 2 THE ROLE OF HIGH TEMPERATURE MATERIALS IN THE HISTORICAL EVOLUTION OF THE TURBINE BLADE SURFACE TEMPERATURE IN AEROENGINES ADVANCED STRUCTURAL MATERIALS MOST AEROSPACE CONCEPTS, THE MAIN LIMITATION TO THIS HYDROGEN-POWERED AND HYDROGEN-COOLED VEHICLE WAS THE AVAILABILITY OF MATERIALSWITH THE REQUIRED COMBINATIONS OFMECHANICALPROPERTIES AND OXIDATION RESISTANCE THIS SHOULD BE IMMEDIATELY APPARENT TO THE READER AFTER REVIEWING FIGURE 1 4, IN WHICH A SCHEMATICOFTHENASPVEHICLE ISPRESENTED NOTETHATTHETEMPERATURE ATTHE NOSEOFTHE X-33DERIVATIVE OF THE PLANE IS AS HIGH AS 18008C ALSO, THE TEMPERATURES IN THE TRAILING EDGES OF THE WING ARE BETWEEN OPERATING TEMPERATURE, °F STRENGTH/WEIGHT RATIO 1 0 X POLYMER MATRIX COMPOSITES CERAMIC MATRIX COMPOSITE NIOBIUM SILICIDE ADVANCED STRUCTURAL MATERIALS CARBON–CARBON COMPOSITES OXIDATION RESISTANCE ADVANCED STRUCTURAL MATERIALS ELEMENTS (FIGURE 1 5) IT IS PERHAPS THE ?RST TEST-BED FOR THE USE OF TITANIUM ALUMINIDE IN AN AEROENGINE APPLICATION THE TOYOTA MOTOR COMPANY OF JAPAN, GENERAL MOTORS, AND FORD MOTOR COMPANY IN THE U S ARE ALSO EXPLORING POSSIBLE APPLICATIONS OF GAMMA TITANIUM ALUMINIDES IN VALVE AND TURBO-CHARGED FIGURE 1 5 CROSS-SECTION OF AEROENGINE THE YF-22 AIRPLANE - APPLICATIONS OF GAMMA TITANIUM ALUMINIDES INDICATED BY ARROWS FIGURE 1 6 APPLICATIONS OF GAMMA TITANIUM ALUMINIDES: (A) TURBO-CHARGER, (B), (C) TURBINE BLADE, AND (D) AUTOMOTIVE VALVE (COURTESY OF THE HOWMET CORPORATION) ADVANCED STRUCTURAL MATERIALS MATERIALS FOR AUTOMOTIVE APPLICATIONS ADVANCED MATERIALS OFFER SOME UNIQUE OPPORTUNITIES IN THE DESIGN OF LIGHTWEIGHT VEHICLES WITH IMPROVED FUEL CONSUMPTION AND PERFORMANCE HOWEVER, LOW COST IS ALSO A VERY STRONG FACTOR IN THE SELECTION AND APPLICATION OF MATERIALS IN THE AUTOMOTIVE INDUSTRY [11] UNLIKE AEROSPACE MATERIALS, ADVANCED STRUCTURAL MATERIALS