Abstract: The formation of borides M_3B_2 M_2B_2 and M_(23)B_6 may be carried out from the melt-quenched Fe_(70)Cr_(18)Mo_2SiB_9 during 700—1150℃ annealing.As the temperature raising,the M_2B,the majority being Fe_2B.may be gradually replaced by Cr_2B via the co-existence between Fe_2B and Cr_2B.The Cr_2B may be formed by trans formation of Fe_2B through the atomic substitu- tion and structural adjustment.The thin slice of remaining Fe_2B is sandwiched between(100) faces of(Cr,Fe)_2B as stacking fault.The M_2B_2 is virtually composed of the Mo_(1+x)(Fe,Cr)_(2-x)B_2 where x(0≤x≤1)increases with the increase of temperature.

Key words: FeCrMoSiB alloy, M_2B, M_3B_2, M_(23)B_6