Fe-8%Ni-Tiマルエージ鋼の析出挙動と機械的性質

抄録

An attempt has been made to survey the effect of the nature of properties, i. e., on the combination of strength and ductility in Fe-8%Ni-1.5%Ti alloys and Fe-8%Ni-1.5%Ti-0.3%Al alloys. It is confirmed that the precipitate contributing to hardening is Ni₃Ti phase (DO₂₁) in higher nickel martensitic alloys and that in lower nickel martensitic alloys NiTi phase (B2) tends to precipitate at lower aging temperatures, by the effect of small amounts of aluminum addition on aging kinetics and hardening response, by transmission electron microscopy and by acrude thermodynamic consideration. For Fe-8%Ni-1.5%Ti alloys, fine and coherent precipitation of NiTi phase on the initial stage of hardening at low aging temperature below 525°C is found to be extremely brittle. On the other hand, semicoherent precipitation of Ni₃Ti η phase at high aging temperature above 525°C results in a better combination of the strength and ductility.