Abstract This work studies the influence of sintering temperature on microstructure and X-ray diffraction patterns of Fe–10% B (wt.) system. The way to obtain these materials is powder metallurgy (P/M) (mixing elemental powders, uniaxial compacting and sintering). Thermal analysis was carried out through dilatometry and differential thermal analysis (DTA). All heat treatments were carried out in argon to avoid steel deborizing. Studied temperatures vary from 1120 to 1400 °C. The influence of carbon (between 0.3 and 0.6 wt.%) and aluminium (4 wt.%) additions were also studied. Microstructural evaluation (optical microscopy and scanning electron microscopy) was done, studying reactions between boron and iron.