Mechanical alloying of Ti-Nb-Si and their consolidation by pulsed current sintering

Ti-xat%Nb-10at%Si (x=5∼40) alloys were synthesized by mechanical alloying (MA) using a planetary ball mill with as starting materials of Ti, Nb and Si powders. The MA powders milled for 360 ks were spherical particles of about 20 μm in all the alloys studied. The characteristics of these MA powders were examined by XRD, DSC and TEM. Ti-5at%Nb-10at%Si powder milled for 360 ks consisted of fine α-Ti crystals. The MA powders containing 10at%Nb to 40at%Nb showed exothermic reaction in the DSC curves. In Ti-20at%Nb-10at%Si and Ti-10at%Nb-10at%Si, the exothermic reactions were observed at higher temperature than 800 K. This exothermic reaction was the crystallization from amorphous phase in MA powder to α-Ti crystalline phase. In Ti-40at%Nb-10at%Si and Ti-30at%Nb-10at%Si, the exothermic reaction was observed at about 600 K. This exothermic reaction was characterized as crystallization from amorphous phase to β-Ti crystalline. The Ti-10at%Nb-10at%Si MA powder was consolidated by the pulsed current sintering with a high pressure. The obtained bulk amorphous compact contained 18vol% pores.