FABRICATION OF PROPELLANT TANKS INVOLVES COSTLY EXTENSIVE MACHINING OF THICK TI-6AL-4V FORGINGS.

FABRICATION OF PROPELLANT TANKS INVOLVES COSTLY EXTENSIVE MACHINING OF THICK TI-6AL-4V FORGINGS. TWO PROMISING APPROACHES FOR TI-15V3CR-3SN AND HOT SUPERPLASTIC FORMING (SPF) OF TI-6AL-4V. SPF REQUIRES LOW FORMING PRESSURE, HAS EXCELLENT SHAPE CAPABILITY AND IS APPLICABLE TO WELL ESTABLISHED TI-6AL-4V. BUT, IT REQUIRES COSTLY TOOLING AND HEATING SYSTEMS. THE PROPOSED PROGRAM WILL INVESTIGATE A NOVEL CONCEPT FOR HEATING AND TOOLING SYSTEMS FOR SUPERPLASTIC FORMING. THE TITANIUM SHEET WILL BE HEATED DIRECTLY WITH LOW HEAT LOSS TO TOOLING. THE PROCESS WILL BE ENERGY EFFICIENT, REDUCE USAGE OF HEAT RESISTANT MATERIALS FOR TOOLING AND ELIMINATE NEED FOR LARGE PRESSES. THE PROCESS FEASIBILITY WILL BE EVALUATED BY MAKING 6 IN. DIAMETER HEMISPHERES FROM 0.070 IN. THICK TI-6AL-4V. PARAMETERS SUCH AS WORK MATERIAL AND TOOLING TEMPERATURES, FORMING PRESSURE AND DEFORMATION WILL BE MONITORED. STARTING AND FINAL MICROSTRUCTURES WILL BE EVALUATED. DATA WILL BE COLLECTED TO JUDGE THE PROCESS FEASIBILITY AND SCALE UP POSSIBILITY.