Investigation of Material Problems for High Temperature, High Power Space Energy-Conversion Systems

摘要

Specific areas of research include investigations of methods of decreasing creep at the high temperatures encountered in the space environment; investigations for improvbing the properties of refractory metals, tungsten in particular, by alloy additions of rhenium, thoria and hafnium carbide; and development of emissivity data for materials of interest at elevated temperatures. The baseline system of tungsten, rhenium alloys is being researched to improve recrystallization characteristics, creep resistance etc. Impurity distributions and their deleterious phenomena are studied. Micro-alloying with thorium and hafnium is being evaluated because of their obvious influences on recrystallization; impurity segregation and embrittlement; solution, precipitation and embrittlement; solution, precipitation and dispersion strengthening; as well as other effects of their intensive gettering capabilities. The alloys are sintered and swaged into rods and wires for various high-temperature mechanical and electronic testing. Testing devices include: a high-temperature thermionic-emission microscope; a specially designed high-temperature vacuum tensile-testing machine; a specially designed and built zone refiner for possible refining conventional metallographic procedures; SEM, TEM and Auger surface analyses.