Abstract
In this work, the microstructural evolution and magnetic performance of the melt-spun amorphous and amorphous-crystalline Fe26.7Co26.7Ni26.7Si8.9B11.0 high-entropy alloys (HEAs) during crystallization were investigated, respectively. Upon heating fully amorphous ribbons, a metastable BCC supersaturated solid solution together with a little Ni31Si12 crystals first precipitated and then the (Fe,Co)2B crystals formed until the full crystallization was achieved. With further increasing temperature after full crystallization, a polymorphic transformation from a metastable BCC phase to two types of FCC solid solutions occurred. For the amorphous-crystalline HEAs, the dominant crystallization products were the metastable FCC but not BCC crystals. During crystallization, the primary metastable FCC crystals first transform into the metastable BCC crystals and then the newly-generated BCC phase transforms into two types of FCC phases with further increasing temperature. This temperature dependence of the gradual polymorphic transformation results in the change of magnetic properties of the present high-entropy amorphous alloys.
Highlights
A novel paradigm for alloy design was proposed based on the mixing of multiple elements in an equimolar or near-equimolar composition [1,2]
The FCC Ni(Si) crystals gradually precipitated within the primary body-centered cubic (BCC) crystals, and the BCC crystals were rich in Fe and Co
The BCC Fe(Co) phase gradually transformed into FCC Fe(Co) phases accompanied by further precipitation of (Fe,Co)2 B and Ni31 Si12 crystals
Summary
A novel paradigm for alloy design was proposed based on the mixing of multiple elements in an equimolar or near-equimolar composition [1,2]. % [1,2] Since their liquid or random solid solution states possess significantly higher mixing entropies than conventional alloys, the designed multicomponent alloys were named as high-entropy alloys (HEAs) [1,2]. Their important microstructural characteristics are that the high configurational entropy of the random mixing of elements usually facilitates the formation of solid solution phases with simple structures [3,4,5,6,7,8] such as face-centered-cubic (FCC), body-centered cubic (BCC), hexagonal close-packed structure (HCP), or a mixture of them [3,4,5,6,7,8,9,10,11,12,13,14,15]. It has been claimed that these promising properties are ascribed to the high-entropy of alloys, the sluggish diffusion, the cocktail effect, and the large lattice distortion of the respective structures [3,4,5,6,7,8,9,12,25,26,27]
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