Effect of composition and milling parameters on the critical ball milling of Ti–Si–B powders

The absence of brittle phases and elevated temperature during ball milling of a powder mixture containing a large amount of ductile component can contribute to reach an excessive agglomeration denoting a critical ball milling (CBM) behavior. This work reports in the effect of composition and milling parameters on the CBM behavior of Ti–Si–B powders. High-purity elemental Ti–Si–B powder mixtures were processed in a planetary ball mill in order to prepare the Ti6Si2B compound and two-phase Ti + Ti6Si2B alloys. TiH2 chips instead of titanium powder were used as a starting material. To avoid elevated temperature in the vials during ball milling of Ti–Si–B powders the process was interrupted after each 10 min followed by air-cooling. Following, the milled powders were hot-pressed at 900 °C for 1 h. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). Short milling times followed by air-cooling contributed to obtain a large amount of powders higher than 75% in the vials. Only Ti and TiH2 peaks were observed in XRD patterns of Ti–Si–B and TiH2–Si–B, respectively, suggesting that extended solid solutions were achieved. The large amount of Ti6Si2B and Ti + Ti6Si2B structures were formed during hot pressing from the mechanically alloyed Ti–Si–B and TiH2–Si–B powders.