The effect of Ta addition on the glass forming ability and mechanical properties of Ni–Zr–Nb–Al metallic glass alloys

The effect of Ta substitution for Zr in the Ni–Zr–Nb–Al metallic glass alloys has investigated by using thermal analysis, X-ray diffractometry and transmission electron microscopy. Small additions of Ta improve the glass forming ability (GFA) of the alloys Ni61Zr28−xNb7Al4Tax (x = 0, 2, 4, 6, 8). The glass transition and crystallization temperatures increase with increasing Ta content up to 8 at.%. The liquidus temperature also increases, but less rapidly, resulting in the increase of Trg and γ values compared with the quaternary Ni–Zr–Nb–Al alloy. Fully glassy rods with the diameter of up to 2 mm can be fabricated by a copper mold casting method. The addition of Ta remarkably improves the plasticity under compression. The compressive strength and macroscopic plastic strain of the bulk metallic glass Ni61Zr24Nb7Al4Ta6 alloy are 3080 MPa and 5%, respectively. The enhanced plasticity can be ascribed to local chemical inhomogeneity resulting from the existence of atom pair with positive enthalpy of mixing in the liquid state.