CRYSTALLOGRAPHY OF CERAMIC PARTICULATE IN METAL-MATRIX COMPOSITES

METAL-PARTICULATE INTERFACES HAVE A MAJOR IMPACT ON THE PROPERTIES OF CERAMIC-REINFORCED METAL-MATRIX COMPOSITES. DESIRED INTERFACE CHARACTERISTICS ARE ADHERENCE, MECHANICAL TOUGHNESS AND RESISTANCE TO ENVIRONMENTAL ATTACK. IN TURN, THESE PROPERTIES ARE DICTATED BY SURFACE MORPHOLOGY, CHEMICAL COMPOSITION, SHAPE AND THE PRESENCE OF THIRD PHASES. STEPS MUST BE TAKEN TO CONTROL THE RELEVANT CHARACTERISTICS OF PARTICULATE TO INSURE THE INTEGRITY OF THESE INTERFACES. CRYSTALLINE ORIENTATION INFLUENCES PARTICULATE DISSOLUTION RATES, SURFACE MORPHOLOGY CHANGES AND GROWTH RATES OF THIRD PHASES DURING PROCESSING. NO RAPID METHOD EXISTS FOR MEASURING SURFACE ORIENTATION OF THE PARTICULATE FACES. THUS THE FABRICATION PROCESS IS "FLYING BLIND" WITH RESPECT TO THE CRYSTALLINE ORIENTATION OF PARTICULATE IN AS-FABRICATED PRODUCT. THE AIM OF THIS RESEARCH IS TO DEVELOP A PRACTICAL DETECTOR FOR MEASURING THE CRYSTALLOGRAPHIC ORIENTATION OF SMALL PARTICLES (>0.25 MICRONS) WITH SPECIAL EMPHASIS ON CERAMICS PARTICLES IN METAL-MATRIX COMPOSITES. THE MEASUREMENT TECHNIQUE IS BASED ON ELECTRON BACKSCATTER DIFFRACTION IN THE SCANNING ELECTRON MICROSCOPE. A HIGH DEGREE OF DETECTION SENSITIVITY AND EFFICIENCY WILL BE ACHIEVED BY EXPLOITING THE SIGNAL AMPLIFICATION BAND ENERGY SELECTIVITY PROPERTIES OF MICROCHANNEL PLATES. THE IMPROVED DETECTION SYSTEM WILL ENABLE RAPID AND STATISTICALLY SIGNIFICANT MEASUREMENTS TO BE ROUTINGELY MADE. SINCE THE DETECTOR WILL BE COMPATIBLE WITH EXISTING SCANNING MICROSCOPES, SPECIMEN PREPARATION WILL BE SIMPLIFIED RELATIVE TO COMPETING METHODOLOGIES, AND ALL WELL-KNOWN SCANNING ELECTRON MICROSCOPY TECHNIQUES FOR DIMENSIONAL, TOPOGRAPHICAL AND ELEMENTAL ANALYSIS TOOLS WILL BE SIMULTANEOUSLY AVAILABLE.