EXPERIMENTAL-DETERMINATION OF PHASE-EQUILIBRIA IN THE FE-AL-C SYSTEM

The phase equilibria in the Fe-Al-C system have been determined betwee n 800 degrees C and the liquidus surface. From cast alloys the liquidu s surface was established. From electron microprobe analyses (EPMA) of quenched samples three isothermal sections at 800, 1000 and 1200 degr ees C have been obtained. Additional high temperature X-ray diffractio n experiments (HT-XRD) yielded three vertical sections and the tempera tures of four invariant reactions. The influence of carbon on the tran sition temperature between the disordered (A2) and the ordered (B2) ct -solid solution was determined from HT-XRD experiments with single cry stals. This transition is shifted remarkably to higher temperatures by the addition of carbon. Special emphasis was placed on establishing t he homogeneity range of the K-phase and its dependence on temperature. This dependence is discussed in terms of order/disorder. In addition, the properties of the K-phase, lattice constant as function of chemic al composition, microhardness and thermal expansion coefficient alpha, have been determined.