Phase separation of BCC phase in the Co-rich portion of Co-Fe-Al system

The α(A2)+ α′(B2) and γ(A1)+ α′(B2) phase equilibria, and the A2/B2 and the ferromagnetic/paramagnetic transitions in the Co-rich portion of Co-Fe-Al system were examined by electron probe microanalysis (EPMA) and differential scanning calorimetric (DSC) measurement. The α(A2)+ α′(B2) two-phase region appears in the Co-rich side of the isothermal section even at high temperatures over 800 °C and a kind of LCST (Lower Critical Solution Temperature)-type phase separation is detected in the Co-30at.%Fe-Al section. Since this phase separation occurs in the compositional range in the vicinity of the intersection of the A2/B2 order-disorder and the magnetic transition boundaries, it seems that the formation of the LCST-type separation results from the enhancive interaction between the chemical ordering and magnetic ordering.