New Zr-based glass-forming alloys containing Gd and Sm

Abstract

The effect of minor additions of Gd and Sm on the glass-forming ability (GFA) of Cu-Zr-Al alloys is investigated here. The rationale for these additions is the fact that the atomic size distribution can increase GFA by changing the topology of the alloy as a function of cluster stability, which is tied to the electronegativity and ionic and covalent nature of alloys. Ingots with nominal compositions of Cu 40 Zr 49 Al 10.5 Gd 0.5 , Cu 40 Zr 49 Al 10.5 Sm 0.5 and Cu 39 Zr 50 Al 9 Gd 2 were prepared by arc-melting and rapidly quenched ribbons were produced by the melt-spinning technique. Bulk samples with a thickness of up to 10 mm were also produced by casting, using a wedge-shaped copper mold. The samples were characterized by differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy. The three compositions showed a fully amorphous structure in the ribbons and a predominantly homogeneous amorphous structure with a thickness of up to 10 mm, although some gadolinium oxide crystals as well as samarium compounds were found to be scattered in the amorphous matrix in 5-mm-thick samples. The amorphous phases in the alloys showed high thermal stability with a supercooled liquid region (∆T x ) of about 70 K.