Hardness, X-ray diffraction, electrical resistivity, and metallography were used to study the annealing of cold-worked zirconium at temperatures from 300-800 C (570-1470 F). Cold work, annealing time, temperature, and furnace atmosphere were chosen as variables. Re crystallization of 25 and 50 per cent cold-worked zirconium occurred by nucleation and growth of new grains and was complete after 10 minutes at 650 C (1200 F) and 620 C (1165 F);100 minutes at 620 (1148 F) and 600 C (1110 F);1000 minutes at 590 C (1095 F) and 550 C (1020 F), respectively. Recrystallization of 10 per cent cold-worked zirconium seemed to proceed by the growth of existing grains within a partially annealed matrix. After 10, 100 and 1000 minute anneals recrystallization was complete at 6'7Q) C (1240 F), 650 C (1200 F), and 610 C (1130 F). For 10, 25, and1. 50 per cent cold-worked zirconium, the as-recrystallized grain size was 0,045, 0.026, and 0.016 mm respectively. Grain growth following recrystallization was negligible. The highest value of n in the equation D kt n , where D is the grain diameter, n and k are constants, and t the time of anneal, was 0.07, describing growth during annealing of 50 per cent cold-worked zirconium. Secondary recrystallization occurred after vacuum anneals at 800 C (1470 F) for long periods of time. Anneals in air or commercial ungettered helium had no effect on recovery, recrystallization, or grain growth kinetics, but did inhibit secondary recrystallization. Impurities were picked up during the air and helium anneals and to a much smaller extent during elevated temperature anneals in vacuum (10 -4 to 10 -5 mm mercury).
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