Fe-36 mass%Ni 合金の熱膨張に及ぼす冷間引抜および焼鈍条件の影響

概要

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Fe-36 mass%Ni alloy, also known as invar alloy, is widely used for precision parts where dimensional change with temperature elevation needs to be minimized. Thermal expansion behavior of the alloy differs by annealing conditions after plastic forming processes; thermal expansion coefficient (TEC) below TC anomalously increases with annealing temperature and reaches a maximum when annealed at 500℃, followed by a decrease to TEC in solution-treated condition when annealed at over 650℃. Neither crystallographic anisotropy nor lattice defects, both of which are introduced by cold deformation, affects the anomalous increase of TEC, since the recrystallization temperature does not coincide with 500℃ and positron lifetime measurement for the sample annealed at the temperature after solution-treatment does not show any emergence of defects. Considering an increase in TC of the sample annealed at 500℃ and a resemblance to the behavior of higher Ni-containing Fe-Ni alloy, this phenomenon might derive from inhomogeneous distribution of Ni atoms resulting in an increase in Fe-Ni pairs by annealing in the temperature range.
日本金属学会 ; 1937-の論文