Training Grant 80NSSC18K1550

THIS SBIR PHASE I EFFORT WILL DEVELOP AND DEMONSTRATE A NOVEL MANUFACTURING PROCESS BASED ON SEVERE PLASTIC DEFORMATION (SPD) TO REFINE AND ENHANCE THE MICROSTRUCTURE-PROPERTIES OF BULK TUNGSTEN. TUNGSTEN, WITH ITS MANY UNIQUE CHARACTERISTICS, PLAYS AN IMPORTANT ROLE IN NUCLEAR REACTORS INCLUDING FOR THE NUCLEAR THERMAL PROPULSION ENGINE. THE REFRACTORY METAL, HOWEVER, STILL HAS A NUMBER OF SHORTCOMINGS WHICH STILL NEED TO BE ADDRESSED. THESE INCLUDE A HIGH DUCTILE-TO-BRITTLE TRANSITION TEMPERATURE, LOW DUCTILITY AND POOR FRACTURE TOUGHNESS, LOW MACHINABILITY AND FABRICABILITY, LOW-TEMPERATURE BRITTLENESS, RADIATION-INDUCED BRITTLENESS, AND A RELATIVELY LOW RECRYSTALLIZATION (RX) TEMPERATURE COMPARED TO ITS OPERATION TEMPERATURE. THE USE OF W ABOVE ITS RX TEMPERATURE INTERMINABLY CAN BE UNSAFE BECAUSE ITS MECHANICAL PROPERTIES DECREASE IN SUCH AN ENVIRONMENT. LOW-TEMPERATURE BRITTLENESS ALSO IMPOSES RESTRICTIONS ON THE APPLICATION OF W AS A STRUCTURAL MATERIAL. AND, GIVEN ITS HIGH HARDNESS, HIGH BRITTLENESS, AND POOR MACHINABILITY, W PARTS CAN BE VERY COSTLY AND TIME-CONSUMING TO MANUFACTURE. PAST EFFORTS TO INCREASE THE DUCTILITY OF W WERE PRIMARILY DIRECTED ON ALLOYING, GRAIN REFINEMENT, EXTREME WORKING, AREA REDUCTIONS, IMPURITY REDUCTIONS, AND HEAT TREATMENTS. WHILE DUCTILE W CURRENTLY EXISTS IN WIRE FORM (E.G., FILAMENTS) THROUGH EXTENSIVE WORKING AND AREA REDUCTION, THIS APPROACH IS CLEARLY NOT PRACTICAL FOR APPLICATIONS WHERE BULK SIZE PARTS ARE NEEDED.