MATRIX ALLOY DESIGN FOR TOUGHENING DISCONTINUOUSLY REINFORCED COMPOSITES

CURRENT ALUMINUM MATRIX COMPOSITES WHICH USE ALLOYS REQUIRING SOLUTION HEAT TREATING, QUNEHCING, AND ELEVATED TEMPERATURE AGING SUFFER FROM POOR TOUGHNESS. IT IS EXPECTED THE TOUGHNESS OF ALUMINUM MATRIX COMPOSITES CAN BE SIGNIFICANTLY INCREASED THROUGH THE USE OF 5000 SERIES ALLOYS WHICH HAVE HIGH WORK HARDENING RATES AND GOOD DUCTILITY. ANY LOSS IN COMPOSITE STRENGTH CAN BE COMPENSATED BY ADJUSTING THE VOLUME FRACTION OF THE SIC PARTICULATE. THE RESULTING COMBINATION OF COMPOSITE STRENGTH AND TOUGHNESS SHOULD BE ENHANCED OVER CURRENT COMPOSITES. OTHER ADVANTAGES OF A 5000 SERIES ALLOY MATRIX INCLUDE: TOUGHNESS IS LESS SENSITIVE TO PURITY LEVEL, RESIDUAL STRESSES FROM QUENCHING ARE ELIMINATED, AND THE COMPOSITES ARE AMENIABLE TO LOW COST CASTING TECHNIQUES TO PRODUCE AS CAST COMPLEX SHAPES OR BILLETS FOR SUBSEQUENT HOT WORKING. MICRO-DEFORMATION STUDIES AS A FUNCTION OF THE CRACK OPENING DISPLACEMENT AND VOLUME FRACTION OF REINFORCEMENT WILL PROVIDE INSIGHT FOR ALLOY DEVELOPMENT.