Fibering of Oxides in Refractory Metals

An investigation of the fibering of oxides by hot deformation in metal matrices was carried out using unalloyed columbium or tantalum as the matrix material and thorium oxide, zirconium oxide, magnesium oxide, or aluminum oxide. Composites were prepared by conventional powder metallurgical techniques and extrusion. The composites were examined for microstructures and fiber length-to-diameter ratio and tested in tension at room temperature and 1100, 2200, 2500, 2750, and 3000 F. Stress-rupture tests were conducted on the composites at 2200 and 2500 F for times up to 1000 hr. It was found that the oxides could be plastically deformed into fibers at temperatures well below their melting points when mechanically worked in a ductile matrix. Composites produced in this way exhibited improved tensile strengths and ratios of tensile strength to density as well as improved stress-rupture strength when compared to additive-free matrix materials and compared favorably with some commercial alloys.