Developing Centimeter-Sized CuZr-based Metallic Glass Composites Via Multi-Element Microalloying

A multi-element microalloying strategy has been implemented to manipulate the microstructure of CuZr-based bulk metallic glass composites (BMGCs) and, in turn, to improve their mechanical properties. It is found that microalloying with a combination of Ti, Hf, Co, Ni and/or Nb/Sn can effectively refine the austenitic B2-CuZr phase, resulting in finely dispersed B2 crystallites embedded in the BMG matrix while enlarging the sizes of BMGCs. Particularly, an optimum BMGC, i.e., Cu40.75Zr42Al4Ag5Sn0.75Co0.5Ti5Hf1Ni1, can be made by coppermold casting in the range of diameter from 6.5 to 13.5 mm, much wider than those of BMGCs obtained from microalloying with merely one or two elements. Meanwhile, this centimeter-sized BMGC possesses good mechanical properties with a fracture strength as high as 1960 MPa and a compressive plastic strain up to 6.8 %. Our results demonstrate that multi-element microalloying would reduce the driving force for nucleation of B2 by lowering the melting entropy, and slow down the B2-growth kinetics by promoting faceted crystal growth while retarding multi-component diffusion, both accounting for the making of centimeter-sized BMGCs that contain finely dispersed B2 crystallites in the glass matrix.