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

Abstract

Bulk glassy alloys with low values of liquidus temperature (T1) and glass transition temperature (Tg) as well as high Tg/T1 were formed at Pt60Cu20P20. Glassy alloys in Pt80-xCuxP20 system were formed over the whole composition range up to 35 at%Cu examined in the present study. The Tg 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 (Tx) increases monotonously with increasing Cu content up to 25 at%Cu and then becomes saturated, leading to a monotonous increase in ΔTx(= Tx - Tg) 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 (Tm) and hence the highest Tg/T1 of 0.61 is obtained for the 20%Cu alloy. The high Tg/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 Tg and T1 and the large ΔTx is important for future development as precision materials for nano-technology which can be deformed through viscous flow.