Designing High Entropy Bulk Metallic Glass (HE-BMG) by Similar Element Substitution/Addition

Abstract

In this paper, we report that two newly designed high entropy bulk metallic glasses (HE-BMGs), Ti20Hf20Cu20Ni20Be20 with a critical diameter of 2 mm, and Ti16.7Zr16.7Nb16.7Cu16.7Ni16.7Be16.7 with a critical diameter of 1.5 mm, can be fabricated by copper mold casting method. These newly developed HE-BMGs exhibited a high fracture strength over 2300 MPa. The glass forming ability and atomic size distribution characteristics of the HE-BMGs are discussed in detail. Moreover, a parameter δ′ was proposed to evaluate the atomic size distribution characteristics in different HEAs. It showed that this new parameter is closely related to the degree of lattice distortion and phase selection of high-entropy alloys. Adjusting the value of δ′ parameter by similar element substitution/addition would be beneficial for designing high entropy bulk metallic glasses.

Composition Design Strategy for High Entropy Amorphous Alloys

“…For Ti20Hf20Cu20Ni20Be20 alloy, Tg, Tx, Tm, and Tl are measured to be 717 K, 760 K, 1095 K, and 1220 K, respectively (Figure 7). Its compressive fracture strength is 2425 MPa for Ø2 mm × 4 mm sample, and it also breaks without plasticity (Figure 8) [54]. For Ti16.7Zr16.7Nb16.7Cu16.7Ni16.7Be16.7 alloy, Tg, Tx, Tm, and Tl are measured to be 684 K, 739 K, 1066 K, and 1218 K, respectively (Figure 7).…”

“…Therefore, a Ti20Hf20Cu20Ni20Be20 alloy was designed. It possesses an amorphous structure and its critical diameter is 2 mm, as shown in Figure 5 [54]. Moreover, Nb and Zr are also very close in the periodic table of elements, so Hf and Nb were added to the Ti20Zr20Cu20Ni20Be20 HE-BMG as a sixth alloying element, respectively.…”

“…Moreover, Nb and Zr are also very close in the periodic table of elements, so Hf and Nb were added to the Ti20Zr20Cu20Ni20Be20 HE-BMG as a sixth alloying element, respectively. Accordingly, Ti16.7Zr16.7Nb16.7Cu16.7Ni16.7Be16.7 with a critical diameter of 1.5 mm (Figure 5) [54] and Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 with a critical diameter of 15 mm (Figure 6a,b) [36] were designed and developed. Surprisingly, the Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 senary HE-BMG possesses a critical size 10 times that of Ti16.7Zr16.7Nb16.7Cu16.7Ni16.7Be16.7 HE-BMG, and it refreshes our cognition about GFA in an equal-atomic high entropy alloy system.…”

“…For Ti 16.7 Zr 16.7 Nb 16.7 Cu 16.7 Ni 16.7 Be 16.7 alloy, T g , T x , T m , and T l are measured to be 684 K, 739 K, 1066 K, and 1218 K, respectively (Figure 7). Its yield strength, fracture strength, and plasticity are 2330 MPa, 2450 MPa, and 0.5% for the Ø1.5 mm × 3 mm sample, respectively (Figure 8) [54]. For the Ti 16.7 Zr 16.7 Hf 16.7 Cu 16.7 Ni 16.7 Be 16.7 alloy, T g , T x , T m , and T l are measured to be 681 K, 751 K, 1019 K, and 1100 K, respectively (Figure 6c).…”

“…Alvi et al reported that a thin film of HfMoNbTaTiVWZr HEAA showed thermal stability up to 750 • C, and it can resist Ar-ion irradiation [53]. Ding et al developed HE-BMG by similar element substitution/addition [54]. Moreover, quinary HEAAs can also be designed from the existing three kinds of ternary BMGs [55].…”