Dynamic recovery and recrystallization behavior caused by fatigue for sintered molybdenum

Nishi, Hiroshi; Enoeda, Mikio; Kawamura, Yoshinori

Powder metallurgy molybdenum and tungsten received severe hot roll reduction after the sintering to reduce the internal defects such as voids. Hence these metals have high stored energy and show unstable microstructures. The molybdenum exhibits cyclic softening being caused dynamic recovery and recrystallization during high temperatures fatigue below its static recrystallization temperature. In this investigation, the observations of microstructures change during high temperatures fatigue are performed and compare to those of static recrystallization. Moreover, the apparent activation energy of the cyclic softening is evaluated to study the mechanisms of the dynamic recovery and recrystallization. The apparent activation energy of the cyclic softening is extremely lower than that of lattice diffusion of molybdenum and the activation energy of lattice diffusion is reduced during high temperatures fatigue.