NONEQUILIBRIUM PHASE CHEMISTRY IN HIGH TEMPERATURE STRUCTURAL ALLOYS

THIS PROJECT WILL DEMONSTRATE A TECHNIQUE FOR RAPID SURVEILLANCE OF THE MICRO-STRUCTURES AND NONEQUILIBRIUM PHASE CHEMISTRY OBTAINABLE THROUGH RAPID SOLIDIFICATION PROCESSING OF ALLOY SYSTEMS. THE METHOD WILL ALLOW AN EFFICIENT IDENTIFICATION AND ANALYSIS OF THE NONEQUILIBRIUM PHASE CHEMISTRIES ESTABLISHED THROUGHOUT THE COMPOSITION RANGE OF INTEREST AND WILL IN PARTICULAR ALLOW DETERMINATION OF BOUNDING VALUES FOR EXTENDED SOLID SOLUTIONOF VARIOUS ELEMENTS. PHASE I WILL EMPLOY A HIGH RATE SPUTTERING PROCESS TO PRODUCE CONTINUOUSLY GRADED RELATIVELY THICK SAMPLES OF SELECTED ALLOY SYSTEMS. THE PROCESS WILL PROVIDE QUENCH RATES ON THE ORDER OF 10 12 K/S, WHICH WILL PROVIDE AN UPPER BOUND TO MATERIALS ACHIEVABLE WITH CURRENT RAPID SOLIDIFICATION TECHNOLOGY. THE ABILITY TO EFFICIENTLY QUANTIFY ALLOY SYSTEMS FOR DETERMINING COMPOSITIONAL AND NONEQUILIBRIUM PHASE CHEMISTRY, BEYOND THE PRESENT ALLOY SYSTEMS PRODUCED WITH CONVENTIONAL RAPID SOLIDIFICATION PROCESS, WILL ALLOW ACCELERATED DEVELOPMENT OF IMPROVED HIGH-TEMPERATURE MATERIALS AND IDENTIFICATION OF POSSIBLE NEW STRENGTHENING MECHANISMS. PHASE I OF THIS PROJECT WILL DEMONSTRATE THE APPROACH ON A TI-AL AND A NI-AL ALLOY. METASTABLE PHASES AND FINE-DISPERSOIDS FORMED IN AS-QUENCHED AND ANNEALED CONDITIONS WILL BE MICROSTRUCTUALLY CHARACTERIZED AND EVALUATED FOR NONEQUILIBRIUM SOLUBILITY AND HIGH-TEMPERATURESTABILITY. PHASE II WILL UTILIZE THE TECHNIQUE TO IDENTIFY COMPOSITIONS AND ESTABLISH RAPID SOLIDIFICATION PROCESSING PARAMETERS TO IMPROVE ELEVATED TEMPERATURE PERFORMANCE OF ALLOY SYSTEMS OF INTEREST TO THE SPONSOR. THE EVALUATIONS SHOULD PROVIDE UPPER BOUND INFORMATION ON ACHIEVABLE MATERIAL PROPERTIES WITH CURRENT OR POTENTIALLY NEAR TERM RS TECHNOLOGY.