Development of a new family of phosphorous-free Pt-based bulk metallic glasses

New BMGs exhibiting strong glass forming ability combined with high hardness have been developed based on the Pt-Si-B ternary system. The effects of partial substitution of platinum by transition metals of the group iron, cobalt, nickel, and copper, as well as the partial replacement of silicon by germanium on the melting temperature, T-m, the crystallization temperature, T-x, the glass transition temperature, T-g, and the hardness are investigated. Amongst the transition metals, nickel and copper were found to reduce the liquidus and the solidus temperatures of the Pt-Si-B near ternary eutectic composition, while cobalt and iron had no influence on the solidus temperature but raised the liquidus temperature significantly. Substitution of one fourth of platinum atoms by either nickel or copper increased the glass transition temperature by roughly 45 K and 65 K, respectively, with a concomitant increase in crystallization temperature of similar magnitude. For a series of alloys with the general formula (Pt0.75Cu0.25)(66.6)B24Si9.4-xGex, increasing substitution of silicon by germanium (x = 0...3) led to a significantly increased crystallization temperature essentially by shifting the first of typically two crystallization peaks to higher temperatures, while the T-g was slightly lowered as x increased. This resulted in a marked widening of the supercooled liquid region, Delta T. Within this alloying series a general trend of increased hardness with increased T-g was observed. (C) 2016 Elsevier B.V. All rights reserved.