Interface Properties of Light Metal Composites through In-Situ

CERTAIN PREPIPITATION HARDENABLE MMC MATRIX ALLOYS DISPLAY MORE RAPID COARSENING AT FIBERMATRIX INTERFACES THAN WITHIN THE MATRIX. UPON AXIAL LOADING, THE PRECIPITATES SERFE AS STRESS INTENSIFERS IN THE PLANE OF THE INTERFACE. THE INTERFACE IS WEAKENED BY REDUCING THE WORK OF DECOHESION, Wd. THIS ENABLES THE DELAMINATION TOUGHENING MECHANISM AND COMPOSITE STRENGTHS ARE GREATLY INCREASED. SINCE THE DECREASE IN Wd IS RELATED TO THE SIZE AND DISTRIBUTION OF PRECIPITATES ON THE INTERFACE, Wd CAN BE SPECIFIED AND CONTROLLED THROUGH SIMPLE HEAT TREATMENT, IF WE UNDERSTAND THE KINETICS OF THE INTERFACE COARSENING PROCESS. WE HAVE DEMONSTRATED THIS EFFECT AND ESTABLISHED KINETICS IN THE Al-CU SYSTEM AND HAVE TERMED THIS PHENOMENA THE DISCONTINOUSLY COATED INTERFACE EFFECT (DCItm). TRANSVERSE AND AXIAL STRENGTHS CAN BE SUBSTANTIALLY IMPROVED THROUGH HEAT TREATMENT ALONE. THE NEED FOR EXPENSIVE FIBER SURFACE COATINGS ARE UNNECESSARY. THE PRINCIPLE OBJECTIVE OF THIS PROGRAM IS TO DEMONSTRATE THIS EFFECT IN INTERESTING HIGH TEMPERATURE Al MATRIX ALLOYS AND MORE COMPLEX TERNARY ALLOYS THAT ARE AGE HARDENABLE REINFORCED WITH ALUMINA (NEXTEL 610) FIBERS. PHASE II WILL CONCENTRATE ON EPLORATION OF MORE COMPLEX ALLOYS, DETAILED KINETIC STUDIES OF HIGHLY PROMISING COMPOSITIONS AND THE ESTABLISHMENT OF A DATA BASE FOR PROMISING SYSTEMS.