Bulk glassy alloys with low liquidus temperature in Pt-Cu-P system

Bulk glassy alloys with low values of liquidus temperature (T₁) and glass transition temperature (T_g) as well as high T_g/T₁ were formed at Pt₆₀Cu₂₀P₂₀. Glassy alloys in Pt_80-xCu_xP₂₀ system were formed over the whole composition range up to 35 at%Cu examined in the present study. The T_g increases significantly with increasing Cu content, shows a maximum value of 522 K at 20%Cu and then decreases slightly with further increase in Cu content. On the other hand, the crystallization temperature (T_x) increases monotonously with increasing Cu content up to 25 at%Cu and then becomes saturated, leading to a monotonous increase in ΔT_x(= T_x - T_g) from 25 K at 0%Cu to 83 K at 35 at%Cu. All the ternary glassy alloys crystallize through a single-stage exothermic reaction, accompanied by the precipitation of mixed Pt₅P₂, Cu₃P and unknown phases. The 20%Cu-containing alloy has the lowest T₁ of 854 K as well as the smallest temperature interval of 21 K between T₁ and melting temperature (T_m) and hence the highest T_g/T₁ of 0.61 is obtained for the 20%Cu alloy. The high T_g/T₁ as well as the low T₁ has enabled us to form bulk glassy alloy rods with diameters up to at least 12 mm by water quenching. The synthesis of the Pt-Cu-P glassy alloys with the low values of T_g and T₁ and the large ΔT_x is important for future development as precision materials for nano-technology which can be deformed through viscous flow.