DEVELOPMENT OF ALUMINUM ALLOYS FOR USE IN - 9OOF FASTENER APPLICATIONS

THERE IS A CHRONIC NEED FOR LIGHTER YET STRONGER MATERIALS FOR BOTH AMBIENT AND ELEVATED TEMPERATURE APPLICATIONS IN BOTH IAILITARY AND COMMERCIAL SECTORS. ONE REQUIREMENT IS FOR A 9OODEGF ALUMINUM FASTENER COMPATIBLE WITH ALUMINUM AND TITANIUM ALLOYS. MECHANICAL ALLOYING/RAPID SOLIDIFICATION PROCESSING USING INTERMETALLIC AND SPINEL DISPERSIONS HAVE DEMONSTRATED PROMISE FOR INCREASING THE SERVICE TEMPERATURE CAPABILITY OF ALUMINUM ALLOYS. HOWEVER, THESE ALLOYING APPROACHES LIMIT THE COMPOSITIONS AND CONCENTRATIONS OF DISPERSIONS OBTAINABLE. BASED ON THE CURRENT UNDERSTANDING OF STRENGTH RETENTION IN HI-BASED SUPERALLOYS TO NEAR THEIR MELTING TEMPERATURES, ALUMINUM BASE ALLOYS WITH MICROSTRUCTURES ANALOGOUS TO THE HI-BASE SUPERALLAYS, CONSISTING OF A FINE DISPERSION OF ORDERED F.C.C. (OR SPINELS) PRECIPITATES IN THE ALUMINUM MATRIX, POSSIBLY IN COMBINATION WITH OTHER DISPERSOIDS LIKE OXIDES, BORIDES, CARBIDES, ETC. WILL BE INVESTIGATED. THIS APPROACH ACHIEVES THE COMBINED EFFECTS OF SEMI-COHERENT PRECIPITATE-MATRIX INTERFACES, ANOMALOUS STRENGTHENING (IN CASE OF LI2-STRUCTURED DISPERSOIDS) AND PINNING OF GRAIN BOUNDARIES AGAINST MIGRATION AT HIGH TEMPERATURES WHICH WILL RESULT IN MECHANICAL PROPERTIES (STRENGTH, DUCTILITY, MODULUS, CREEP RESISTANCE, ETC.) ADEQUATE FOR >9OODEGF FASTENER APPLICATIONS. A UNIQUE BUT DEMONSTRATED PLASMA SYNTHESIS PROCESS DEVELOPED AT MER WILL AFFORD GENERATION OF MICROSTRUCTURES WITH COMPOSITIONS AND CONCENTRATIONS OF DISPERSOIDS HERETOFORE UNOBTAINABLE.