TITANIUM ALUMINIDE ALLOYS PREPARED VIA RAPID SOLIDIFICATION TECHNOLOGY

ALLOYS BASED ON INTERMETALLIC TI(3)AL HAVE BEEN RECOGNIZED AS POTENTIAL MATERIALS TO BE DEVELOPED FOR HIGH TEMPERATURE APPLICATIONS IN ADVANCED WEAPON SYSTEMS AND AEROSPACE VEHICLES. TITANIUM ALUMINIDES POSSES LOW DENSITY, HIGH STRENGTH AND GOOD OXIDATION RESISTANCE, BUT SUFFER FROM POOR ROOM TEMPERATURE DUCTILITY. THE MAJOR CAUSES FOR LOW ROOM TEMPERATURE DUCTILITY HAVE BEEN IDENTIFIED AS (1) EXTENSIVE PLANAR SLIP AND (2) LIMITED NUMBER OF SLIP SYSTEMS DUE TO THE ORDERED CRYSTAL STRUCTURE OF TI(3)AL. EXTENSIVE PLANAR SLIP LEADS TO STRESS CONCENTRATION AT THE GRAIN BOUNDARIES. SUITABLE MICROSTRUCTURAL MODIFICATIONS CAN BE MADE THROUGH ALLOYING AND PROCESSING TO CIRCUMVENT THESE PROBLEMS. WE PROPOSE A RESEARCH PROJECT TO STUDY THE STRUCTURE AND PROPERTIES OF MICEO-ALLOYED TITANIUM ALUMINIDES PROCESSED VIA RAPID SOLIDIFICATION TECHNOLOGY. TI(3)AL WILL BE ALLOYED WITH BETA STABILIZER, MO, AND MICRO-ALLOYED WITH BORON AND CARBON. MO WILL BE ADDED TO RETAIN CERTAIN AMOUNT OF BCC PHASE IN ORDER TO PROMOTE DUCTILITY. MICRO-ALLOYING WITH B AND C IS EXPECTED TO IMPROVE THE GRAIN BOUNDARY COHESIVITY. RAPID SOLIDIFICATION PROCESSING WILL LEAD TO AN EXTREMELY FINE GRAIN STRUCTURE, WHICH WILL REDUCE THE SLIP-DISTANCE TO DECREASE STRESS CONCENTRATIONS AT THE GRAIN BOUNDARIES. A RANGE OF ALLOY COMPOSITONS WILL BE STUDIED, AND THE MECHANICAL PROPERTIES OF MODIFIED TI(3)AL WILL BE EVALUATED AS A FUNCTION OF HEAT TREATMENTS AND MICROSTRUCTURAL CHARACTERIZATION.