Improving the strength and the toughness of Mg–Cu–(Y, Gd) bulk metallic glass by minor addition of Nb

Mg65Cu25Re10 (Re = Y, Gd) and Mg64Cu25Nb1Re10 (Re = Y, Gd) bulk metallic glasses (BMGs) have been fabricated by copper mould casting. It is shown that the minor addition of Nb can not only increase the thermal stability but also improve the fracture strength and the toughness of the Mg-based BMG alloys greatly. The fracture strength of Mg64Cu25Nb1Y10 and Mg64Cu25Nb1Gd10 reaches as high as 1023 MPa and 973 MPa, respectively. The Young's modulus has also been increased by the addition of Nb. From the fracture morphologies of the Nb bearing Mg-based BMG alloys, it is known that the size of plastic deformation zone can be increased to micrometer scale. This work proves that it is possible to improve the strength and toughness of Mg-based BMG by adding an element having positive heat of mixing with the constituent elements.