The effect of Ta addition on mechanical properties of Zr-based bulk metallic glasses

Bulk metallic glasses (BMGs) exhibit poor room temperature plasticity, so improving their room temperature plasticity is important for amorphous alloys in engineering applications. In this paper, Zr60Cu(20-x)Al10Ni10Tax (x = 0, 1, 3, 5) bulk metallic glasses with 3 mm diameter rods were prepared by water-cooled copper mold suction casting, and investigated the effect of minor additions of Ta on the properties of Zr-Cu-Ni-Al alloys, especially on plasticity. The results show that the Zr-based alloys with a 3 mm diameter are amorphous. With the addition of Ta elements, the glass transition temperature hardly changed, the crystallization onset temperature increased from 747 K to 767 K, the width of the supercooled liquid phase zone increased from 49 K to 68 K, and the thermal stability of the alloy was improved. The room temperature uniaxial compression test found that with the increase of Ta content, the strength and plasticity of alloys showed a trend of first increasing and then decreasing, when the Ta content was 1 at.%, more interactive shear bands were observed on the side surface of the alloy after compression, while the fracture surface exhibited a complete vein pattern, and fracture strength and plasticity of samples reached to 1920 MPa and 13.8%, respectively. The results of nanoindentation tests indicated that when the Ta content was 1 at.%, the alloy exhibited the maximum indentation hardness and elastic modulus of 8.03 GPa and 101.48 GPa, respectively. It can be concluded that the right amount of Ta in Zr-based BMGs improves the mechanical properties, especially, the fracture strength, the plasticity, the indentation hardness, and the elastic modulus.