HIGH-RESOLUTION ELECTRON-MICROSCOPY OBSERVATION OF THE GAMMA-PHASE INTI4AL3NB ALLOY

In the alloy Ti3Al-Nb, several phases appear after cooling at various rates from a high temperature. These are B2, D0(19) (alpha(2)-phase), L1(0) (gamma-phase) and an omega-type phase. A high-resolution electro n microscopy observation is presented of an alloy continuously cooled at 10 K s(-1) from 1200 degrees C, which shows very small regions of t he gamma-phase at the boundaries between the alpha(2)-phase and B2 pha se. An opportunity is thus provided to observe the early stages of the formation of the gamma-phase. Orientation relationships for the phase s are given.