Glass forming ability and mechanical properties characterization on Mg_(58)Cu_(31)Y_(11-x)Gd_x bulk metallic glasses

摘要

Mg-Cu-Y-(Gd) alloy rods are made by arc-melting and injection casting methods in this research. The improvement of glass forming ability and mechanical properties by using Gd to substitute Y in Mg_(58)Cu_(31)Y_(11) bulk metallic glasses (BMGs) is of interest. The results of thermal analysis present that the Mg-Cu-Ybase alloys with the addition of 6 and 8 at percent Gd are the best BMG former. The Vickers indentation tests and the compression tests are carried out in order to explore the mechanical properties of alloys. It reveals that there is no obvious change in Young's modulus (approx 45 GPa) of the Gd-containing Mg-based BMG, in contrast with the base alloys. Vickers (micro-) indentation fracture toughness measurements are performed for comparison. Shear bands and the corner cracks around the inverted pyramind mark are showed. An average fracture toughness of Mg-Cu-Y-Gd alloy is calculated asa pprox 4 MPa m~(1/2), which is a little higher than that of base alloys studied in the paper. Meanwhile, the fracture surface of Mg-based BMGs is dominant by featureless mirror-like and river-like pattern. Only nano-scaled shear bands and vein patterns are displayed, indicating that the plasticity of the Mg-Cu-Y-Gd BMGs are shown in nano-scale indeed.