2001 年 41 巻 8 号 p. 866-875
Koistinen and Marburger's equation relating volume fraction of athermal martensite to temperature has been applied to diffusional transformation dilatometry data obtained on continuous cooling Fe–15%Ni alloys. After austenitising for 1 h at 1 000°C and cooling at 50 K/min (0.83 K/s), grain boundary nucleated massive ferrite was observed which developed into Widmanstätten ferrite with a ferrite habit plane of {110}b for temperatures between 372°C and 352°C. On cooling at 44 K/s from 1 000°C bainitic ferrite was observed for temperatures below 360°C. There was some retained austenite in this bainitic structure giving a ferrite habit plane of {110}b parallel to the austenite plane {111}f. Cooling at the same rate, 44 K/s from 1 200°C gave lath martensite below the Ms of 261°C with a ferrite habit plane of {112}b. Superlattice spots corresponding to the DO3 or B2 structure were observed in electron diffraction patterns on cooling at 50 K/min (0.83 K/s) and 44 K/s from 1 000°C.
