マルテンサイト系Fe-Ni-Be合金の析出硬化に関する研究
1969 年 55 巻 1 号 p. 48-58
詳細
1969 年 55 巻 1 号 p. 48-58
Age hardening behaviours and precipitation process of martensitic Fe-5%Ni-Be alloys were investigated. The results obtained were as follows:
(1) Fe-5%Ni-Be alloys containing 0.47%Be or above were remarkably hardened by aging in the temperature range between 400°C and 550°C after water-quenched from austenite region.
(2) There were two types of equilibrium precipitates in the aged alloy. One was finely distributed general-type precipitate, and the other was stringer-like one produced by grain boundary reaction. Both of them were CsCl type NiBe having lattice parameter of about 2.62Å. The reaction was suppressed by the addition of small amount of Ti or Zr, accompaniedby significant improvement of hardening.
(3) Through the transmission electron microscopy and X-ray diffraction analysis, . it is considered that the alloys are hardened by the formation of clusters with ordered structure rich in solute arom on the matrix lattice.
(4) General-type precipitates were formed with the same orientation as the bcc martensite matrix. However, as the misfit of the two bcc lattices was relatively large, the coherency strain and in the lattice was possibly lost and the specimen was over-aged by the precipitation. Double diffraction phenomenon was often observed on the diffraction patterns from the precipitated specimens.
(5) Fe-5%Ni-Be alloys showed reversion phenomenon when they were re-heated for short period at e. g. 625°C after pre-aged for 7hr at 450°C.
