Abstract
The mechanism of precipitation hardening in Fe-Ni-Cr-Ti alloy was studied by microhardness test, thermal dilatation measurement, X-ray diffraction, optical and transmission electron microscopy. The results show that the mechanism of precipitation hardening in Fe-Ni-Cr-Ti alloy is similar to those in Fe-Ni-Ti alloy. It is an advantageous nature of this alloy that the heat treatment which gives a good constant modulus charactaristic agrees with that which gives excellent mechanical properties. That is, when Fe-Ni-Cr-Ti alloy was aged for 2 hr at 600°C, the η phase precipitates in proper distribution and the alloy is strengthened; after the η phase precipitates, the composition of the γ phase resembles that of Elinvar and the thermoelastic coefficient approaches zero.
