Solid-state synthesis of new glassy Co65Ti20W15 alloy powders and subsequent densification into a fully dense bulk glass

The mechanical alloying method was used to synthesize a single glassy phase of Co65Ti20W15 alloy powders, using a high-energy ball mill. The glass transition temperature of the end-product, which was obtained after 173 ks of milling time, lies at 786 K, whereas the crystallization takes place at 878 K through a single sharp exothermic peak with an enthalpy change of crystallization of −4.37 kJ/mol. The reduced glass transition temperature was found to be 0.51. This glassy alloy powders exhibit a very large supercooled liquid region (92 K) for a ternary metallic system. The spark plasma sintering method was used to consolidate the glassy powders under an argon gas atmosphere at 843 K with a pressure of 19.6–38.2 MPa. The sample that was consolidated within 180 s maintains its chemically homogeneous glassy structure with a relative density of above 99.6%. Neither the supercooled liquid region nor crystallization temperature was affected by such a rapid consolidation procedure. Thus, the thermal stability of the bulk glassy sample is almost identical with the original glassy powders. The Vickers microhardness of the bulk glassy Co65Ti20W15 reveals high values, ranging between 8.69 and 8.83 GPa. The fabricated bulk glassy alloy shows high compressive strength of 2.44 GPa with a Young’s modulus of 176.81 GPa. Neither yielding stress, nor plastic strain could be detected for this glassy alloy, which its elastic strain is 1.33%.