NOVEL HIGHER TEMPERATURE ALUMINUM ALLOYS BY RAPID CONSOLIDATION OF GLASSY STRUCTURES

NASA IS INTERESTED IN NEW ALUMINUM ALLOYS OF NON-EQUILIBRIUMCHEMISTRIES WITH THE OBJECTIVE OF INCREASING THE UPPER-USE TEMPERATURE BY 200F. PRIOR ART HAS DEALT WITH THE USE OF RAPID SOLIDIFICATION TO FORM FINE-GRAINED CRYSTALLINE ALLOYSBASED ON AL-FE-V-SI, AL-FE-CE, AND AL-FE-MO-V. ALTHOUGH THESE ALLOYS HAVE SHOWN PROMISE IN IMPROVING USE TEMPERATURE, SIGNIFICANT FURTHER IMPROVEMENT COULD BE MADE BY CONTROLLED CRYSTALLIZATION AND CONSOLIDATION OF RECENTLY DEVELOPED, HIGH-CRYSTALLIZATION-TEMPERATURE GLASSY ALLOYS (TC=450C). HOWEVER, CONVENTIONAL CONSOLIDATION PROCESSES SUCH AS HOT PRESSING AND HOT ISOSTATIC PROCESSING ARE NOT AMENABLE TO SIMULTANEOUS REQUIREMENTS FOR FULL DENSITY, SMALL GRAIN SIZE, AND LOW COST. RECENTLY, A QUASI-ISOSTATIC, HIGH-PRESSURE CONSOLIDATION PROCESS DEVELOPED BY THE FIRM ENABLES CONSOLIDATION AT SHORT TIMES (5-30 SECS.) AND AT LOWER TEMPERATURES THAN HOT ISOSTATIC PROCESSING, WHILE ACHIEVING FULL DENSITY. PHASE I WILL EVALUATE THE FEASIBILITY OF PRODUCING FULLY DENSE, ULTRA-FINE-GRAINED ALUMINUM ALLOYS BY CONTROLLED CRYSTALLIZATION OF A GLASSY ALUMINUM AL-SI-FE-Y ALLOY THAT IS THERMALLY STABLE TO HIGH TEMPERATURES. PHASE I IS EXPECTED TO SHOW THAT THE GOAL OF ATTAINING 200F INCREASES IN USE TEMPERATURE OF ALUMINUM ALLOY IS FEASIBLE. THE DATA GENERATED IN PHASE I WILL ENABLE PHASE II TO FOCUS ON UPSCALED FABRICATION OF LARGE BILLETS AND WILL INVOLVE EVALUATION OF METAL WORKING TO FORM SHEETS, FORGINGS, AND PLATES. EXTENSIVE MECHANICAL TESTING WILL ALSO BE CARRIED OUT IN PHASE II. NASA IS INTERESTED IN NEW ALUMINUM ALLOYS OF NON-EQUILIBRIUMCHEMISTRIES WITH THE OBJECTIVE OF INCREASING THE UPPER-USE TEMPERATURE BY 200F. PRIOR ART HAS DEALT WITH THE USE OF RAPID SOLIDIFICATION TO FORM FINE-GRAINED CRYSTALLINE ALLOYSBASED ON AL-FE-V-SI, AL-FE-CE, AND AL-FE-MO-V. ALTHOUGH THESE ALLOYS HAVE SHOWN PROMISE IN IMPROVING USE TEMPERATURE, SIGNIFICANT FURTHER IMPROVEMENT COULD BE MADE BY CONTROLLED CRYSTALLIZATION AND CONSOLIDATION OF RECENTLY DEVELOPED, HIGH-CRYSTALLIZATION-TEMPERATURE GLASSY ALLOYS (TC=450C). HOWEVER, CONVENTIONAL CONSOLIDATION PROCESSES SUCH AS HOT PRESSING AND HOT ISOSTATIC PROCESSING ARE NOT AMENABLE TO SIMULTANEOUS REQUIREMENTS FOR FULL DENSITY, SMALL GRAIN SIZE, AND LOW COST. RECENTLY, A QUASI-ISOSTATIC, HIGH-PRESSURE CONSOLIDATION PROCESS DEVELOPED BY THE FIRM ENABLES CONSOLIDATION AT SHORT TIMES (5-30 SECS.) AND AT LOWER TEMPERATURES THAN HOT ISOSTATIC PROCESSING, WHILE ACHIEVING FULL DENSITY. PHASE I WILL EVALUATE THE FEASIBILITY OF PRODUCING FULLY DENSE, ULTRA-FINE-GRAINED ALUMINUM ALLOYS BY CONTROLLED CRYSTALLIZATION OF A GLASSY ALUMINUM AL-SI-FE-Y ALLOY THAT IS THERMALLY STABLE TO HIGH TEMPERATURES. PHASE I IS EXPECTED TO SHOW THAT THE GOAL OF ATTAINING 200F INCREASES IN USE TEMPERATURE OF ALUMINUM ALLOY IS FEASIBLE. THE DATA GENERATED IN PHASE I WILL ENABLE PHASE II TO FOCUS ON UPSCALED FABRICATION OF LARGE BILLETS AND WILL INVOLVE EVALUATION OF METAL WORKING TO FORM SHEETS, FORGINGS, AND PLATES. EXTENSIVE MECHANICAL TESTING WILL ALSO BE CARRIED OUT IN PHASE II.