Near-equiatomic high-entropy decagonal quasicrystal in Al 20 Si 20 Mn 20 Fe 20 Ga 20
- PDF / 9,066,215 Bytes
- 8 Pages / 595.276 x 793.701 pts Page_size
- 93 Downloads / 252 Views
Published online 21 September 2020 | https://doi.org/10.1007/s40843-020-1441-3
Near-equiatomic high-entropy decagonal quasicrystal in Al20Si20Mn20Fe20Ga20 1†
1†
2
1
1
3
3
Haikun Ma , Liangqun Zhao , Zhi-Yi Hu , Dinghao Miao , Ruixuan Li , Tulai Sun , He Tian , 1 1 1 1* Tiantian Zhang , Hua Li , Yong Zhang and Zhanbing He ABSTRACT High-entropy alloys (HEAs) contain multiple principal alloying elements, but usually with simple crystal structures. Quasicrystals are structurally complex phases, but are generally dominated by only one element. However, nearequiatomic high-entropy quasicrystals have rarely been reported because they are difficult to prepare experimentally and predict theoretically. Therefore, the preparation and crystal structures of near-equiatomic high-entropy quasicrystals have drawn much interest. We report a quinary decagonal quasicrystal (DQC) with near-equiatomic alloying elements in Al20Si20Mn20Fe20Ga20 melt-spun ribbons, which is the first to our knowledge. Meanwhile, the structural features of the DQC are characterized in detail. The configurational entropy of both the alloy and DQC satisfies the entropy-based criterion for HEAs, suggesting a high-entropy DQC. Our findings provide a new strategy to develop high-entropy quasicrystals. Keywords: high-entropy alloys, decagonal quasicrystal, highentropy quasicrystals, melt-spun ribbons, high-angle annular dark-field scanning transmission electron microscopy
INTRODUCTION The first icosahedral quasicrystal was discovered by Shechtman in quenched Al-Mn alloys in 1984 [1], and hundreds of quasicrystals have since been reported [2]. Quasicrystals were mainly discovered in binary and ternary Al-based alloys [2–7], usually with an Al content of 60 at% to 85 at% (at%, atomic percent) [8]. In addition, quasicrystals were found in other systems such as Mgbased and Ga-based alloys [9–12]. Most quasicrystals are dominated by only one element; quasicrystals with multiple principal alloying elements have rarely been dis-
covered. High-entropy alloys (HEAs) were first independently reported in 2004 by Yeh et al. [13] and Cantor et al. [14]. Different from the traditional alloys, HEAs are not based on one or two major elements, but are composed of multiple principal alloying elements. They usually contain at least five principal elements in equal or near-equal atomic percentages [15]. The definition of HEAs has been extended from equiatomic alloys to alloys with sufficiently high configurational entropy (ΔSconf) to overcome the effect of enthalpy [16]. Alloys with a ΔSconf greater −1 −1 than 1.5R (R=8.31 J K mol , the gas constant) are usually defined as HEAs [17,18], and non-equiatomic HEAs have also been developed [16]. The phase structures of reported HEAs contain solid solutions, intermetallics, and amorphous phases [19,20]. Among them, the face-centred cubic (FCC) [14,21–25] and body-centred cubic (BCC) [26–29] solid-solution HEAs are by far the most extensively investigated. Furthermore, hexagonal close-packed (HCP) structures [30– 35], ordered int
Data Loading...
