Synthesis and fundamental properties of Cu-based bulk glassy alloys in binary and multi-component systems

A glassy phase containing cubic phase particles with a size of 3–5 nm was formed in cast Cu60Zr30Ti10 and Cu60Hf30Ti10 bulk alloys. The cubic phase is in a metastable state and its lattice parameter (a0) is 0.45 nm for the former alloy and 0.51 nm for the latter. These bulk alloys exhibit good mechanical properties of 2000–2130MPa for tensile strength (t,f), 2060–2160MPa for compressive strength (c,f) and 0.008–0.017 for compressive plastic strain ("c,p). The temperature interval of the supercooled liquid (SL) region prior to crystallization is 37K for Cu60Zr30Ti10 and 67K for Cu60Hf30Ti10. The primary crystallization occurred by precipitation of cubic CuZr (a0 0:35 nm) in a diffusion-controlled growth mode of nuclei and an orthorhombic Cu8Hf3 phase in an interface diffusion-controlled growth of nuclei with decreasing nucleation rate. The difference in the precipitation modes is interpreted to be the origin of the difference in the SL region. Furthermore, the addition of Al to Cu-Zr and Cu-Hf alloys caused the formation of a glassy single phase in the rod form with diameters up to at least 3mm, though bulk glassy alloy rods with critical diameters up to 1.5mm and c,f of 1920–2260MPa were formed in Cu-Zr and Cu-Hf binary systems. The ternary bulk glassy alloys exhibited high c,f of 2100–2370MPa with "c,p of 0.002–0.006. The addition of Pd, Pt, Ag or Au increased Tx and a large Tx of 102–110K was obtained for the Cu-Hf-Al-M (M=Pd or Ag) glassy alloys. The synthesis of Cu-based bulk glassy alloys with good mechanical properties and large Tx in glassy single, and mixed glassy and cubic phase states, is important for future applications of bulk glassy alloys