18%Ni マルエージング鋼におけるα'→γ逆変態

概要

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Mechanism of α'→γ reverse transformation has been examined by means of dilatometric measurements, X-ray analysis and structural observations in an 18% Ni maraging steel. The mechanism is changed in the range of heating rate between 100 and 500℃/min. At the lower heating rates, the stabilization (decrease in Ms and increase in the content of retained γ) and the unstabilization (increase in Ms) of reverted γ are observed, and this phenomenon is concerned with the partitioning of the solute atoms in α' during heating. Under these conditions, surface relieves are observed during the reverse transformation and γ grain boundaries inherit the former features completely when heated to the temperature range from Af to γ recrystallization temperature. From the above results, the mechanism of α'→γ reverse transformation at lower heating rates is inferred as follows ; first, α' is partitioned to solute rich and solute poor regions by short range diffusion, and in the subsequent α'→γ transformation, martensitic character participates partially. On the other hand, at the higher heating rates, either stabilization or unstabilization of the reverted γ is not observed, and accordingly it is considered that α' transforms to γ martensitically without the diffusion process.
社団法人日本鉄鋼協会の論文
1978-04-01