マルテンサイト系Fe-Ni-Si合金の析出硬化に関する研究

抄録

Age hardening behaviours and precipitation process of martensitic Fe-Ni-Si alloys containing 10-18% Ni and 0-5% Si were investigated. The results obtained are summarized as follows:
1) Fe-Ni-Si alloys having lath martensite structure were remarkably hardened by aging in the temperature range between 300 and 525°C after water quenched from austenite region.
2) When aged isothermally at 500°C or below, the age-hardening process of the Fe-Ni-Si alloys took place in two stages.
3) The first stage of hardening, which was accompanied by increment of electric resistivity and slight contraction of lattice parameter of martensite matrix, seems to be due to the formation of solute rich clusters (or zones) in the bcc matrix. In the electron diffraction patterns from thin foil specimen, there were faint super lattice spots suggesting the clusters are ordered (DO₃ type) ones.
4) In the second stage of hardening, electric resistivity decreased and lattice parameter of martensite increased. Observations by transmission electron microscopy indicated that the hardening of the second stage seems to be due to the precipitation of a transition phase on dislocations.