B 2 structure of high-entropy alloys with addition of Al

Abstract

A series of AlCrCoNiFe based alloys with equal percentage of principal components (high-entropy alloys or HE alloys) is fabricated. The related crystalline structures of the alloys are measured and calculated. Results show that the formed bcc phase is a compound based B2 structure where there is partial ionic bonding between Al and other transition metals. Thus, the bcc structure of the alloys should be a B2 instead of an A2 due to the large difference in electronegativities among the components consisting of the HE alloys.

The Al Effects of Co-Free and V-Containing High-Entropy Alloys

“…Otto et al [8] investigated various factors which affect the phase stability of HEAs, and concluded that multiple phased microstructures, as well as intermetallic phases, would be formed when the enthalpy had greater influences than configurational entropy. Therefore, based on the viewpoints and results of the present study, it was expected that as the Al content increased, the Al and Ni elements would more easily be combined to form a B2 phase, due to the strongly negative formation enthalpy of B2 structure for AlNi [32]. When x = 0.5, along with the coherent A2/B2 phases, the unknown phases which contained large amounts of V and Cr were distributed in the alloy in the form of nano-precipitates.…”

Effect of aluminum contents on microstructure and properties of AlxCoCrFeNi alloys

“…Since FCC or L12 structure cannot be observed in Xray diffraction experiment, the percentage of FCC or L12 structure should be smaller than 5%. The existence of or FCC or L12 should be related to the inhomogeneous distribution of Al in the alloy where Al content is small, as reported in references [21,22]. B2 should be a more possible structure since Al and Ni as essential components have a high formation enthalpy H c AlNi , which leads to that Al and Ni should hold the sites of center and corner in B2, respectively.…”

Determination of the transition to the high entropy regime for alloys of refractory elements

“…In the last decade, the number of systems studied experimentally has grown substantially [9,10]. Numerous compositions of n-element alloys (n > 5) have been studied experimentally [10][11][12][13][14][15][16][17][18][19][20][21], all showing that HEA tend to form simple crystal structures (bcc or fcc solid solutions or a combination of both). Experimental studies also include the role of constituents or alloying additions on properties [22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”