Pseudo-quinary Ti_(20)Zr_(20)Hf_(20)Be_(20)(Cu_(20-x)Ni_x) high entropy bulk metallic glasses with large glass forming ability

摘要

A series of pseudo-quinary Ti_(20)Zr_(20)Hf_(20)Be_(20)(Cu_(20-x)Ni_x) (x = 2.5,5,7.5,10,12.5,15,17.5 and 20 at.%) 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 12 mm. In particular, the developed Ti_(20)Zr_(20)Hf_(20)Be_(20)(Cu_(7.5)Ni_(12.5)) and Ti_(20)Zr_(20)Hf_(20)Be_(20) high entropy alloys (HEAs) can be produced in the amorphous state with diameters up to 30 mm and 15 mm, 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.