Pseudo-quinary Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu_20-xNi_x) high entropy bulk metallic glasses with large glass forming ability

A series of pseudo-quinary Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu_20-xNi_x) (x=2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20at.%) high entropy bulk metallic glasses (HE-BMGs) with large glass forming ability (GFA) were successfully prepared by copper mold tilt-casing. The critical diameters (D_c) of these HE-BMGs are all above 12mm. In particular, the developed Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu_7.5Ni_12.5) and Ti₂₀Zr₂₀Hf₂₀Be₂₀Ni₂₀ high entropy alloys (HEAs) can be produced in the amorphous state with diameters up to 30mm and 15mm, respectively, which are the largest HE-BMG and quinary HE-BMG hitherto. The two HE-BMGs also exhibit high yield strength, together with the plastic strain values of (3.0±1.1) % and (4.0±0.9) %, respectively. With increasing Ni additions in the pseudo-quinary HEAs, the crystallization growth resistance and thermal stability have been improved, which is apparently due to the sluggish diffusion of the atoms in the HEAs.