Part II – February 1968 - Communication - Recrystallization in Alpha Plutonium

The purpose of this technical note is to briefly present some data on a phenomenon—recrystallization with concurrent deformation—that has been found to occur in a plutonium. This phenomenon is unusual because a plutonium is considered brittle, not easily deformed, and not easily recrystallized; the a phase is simple monoclinic having 8 atoms per unit cell and it is stable below about 115°C. The properties of the recrystallized metal were different from the as-cast metal. Even though a plutonium is difficult to deform, Ianniello successfully rolled it' and he also observed some recrystallization at 120°C.2 Pavlick and Hanson3 detected some recovery at 109°C but they observed no recrystallization. Gardner4 and Bronisz5 studied the compression properties up to 100°C but they did not report having seen recrystallization. In the present deformation studies of electrorefined plutonium pronounced recrystallization took place concurrently with plastic deformation in compression between 24" and 115°C. The metal contained less than 300 ppm total impurities with the major impurities being 100 ppm Am, 30 ppm C, 40 ppm W, and 25 ppm U; all other impurities totaled less than 100 ppm. The compression specimens were machined to dimensions of 1.2 cm long and 0.8 cm diam from as-cast rods having a density of 19.65 g per cu cm. They were heated to the test temperature in a high-temperature silicone fluid that was evacuated to 10-4 Torr. With this procedure the specimens oxidized a negligible amount, and the temperature was maintained within ±0.2°C for times up to 3 weeks. Deformation and recrystallization