REDUCTION OF CONSOLIDATION STRESS IN CERAMIC REINFORCED METAL MATRIX COMPOSITES

METAL MATRIX COMPOSITES (MMC) OFFER COMPARABLE MICROCREEP RATES (MCR) AT A FRACTION OF THE COST FOR SPECIALLY PROCESSED ALLOYS IN STABLE MEMBER APPLICATIONS. RESIDUAL STRESSES ARE IMPORTANT TO CONTROL WHEN PARTS PER MILLION OF STRAIN ARE A CONCERN. LARGE VOLUME FRACTIONS OF CERAMIC REINFORCEMENT IN COMPOSITES WILL CONTRIBUTE TO BOTH THE MACRO AND MICRO RESIDUAL STRESSES. THE PROPOSED PROGRAM WILL INVESTIGATE THE USE OF A WORK HARDENING ALLOY (I.E. AL-MG) RATHER THAN PRECIPITATION HARDENED ALLYS (I.E. AL-ZN AND AL-CU) FOR STABLE MEMBER COMPONENTS. X-RAY DIFFRACTION TECHNIQUES WILL BE USED TO MEASURE THE MACRO AND MICRO RESIDUAL STRESSES, MICRO-CREEP TESTS WILL BE CONDUCTED, AND THE USE OF UP-QUENCHING (I.E., QUENCHING IN LIQUID NITROGEN) WILL BE INVESTIGATED AS A MEANS TO CONTROL RESIDUAL STRESSES. PHASE I WILL INCLUDE DEVELOPING A TEST TECHNIQUE FOR COMPARING THE RE-LATIVE MICROCREEP RATE AMONG SEVERAL CONDITIONS OF ALLOYS AND PROCESSES. THE BEHAVIOR OF A WORK HARDENING AND A PRECIPITATION HARDENING MATRIX ALLOY WILL BE COMPARED. LONG TERM AND STATISTICALLY SIGNIFICANT DATA WILL BE DEVELOPED IN PHASE II FOR DIFFERENT ALLOYS. PROCESSING BY UP-QUENCHING CYCLING TO CONTROL RESIDUAL STRESSES WILL ALSO BE EVALUATED. PHASE III WILL MANUFACTURE A COMPONENT USING THE BEST COMBINATION OF MATRIX ALLOY AND PROCESSING FROM PHASE II AND THE MCR RESULTS VERIFIED.