Abstract
A CoCrCuFeNiTi0.8 high-entropy alloy was prepared using directional solidification techniques at different withdrawal rates (50 μm/s, 100 μm/s, 500 μm/s). The results showed that the microstructure was dendritic at all withdrawal rates. As the withdrawal rate increased, the dendrite orientation become uniform. Additionally, the accumulation of Cr and Ti elements at the solid/liquid interface caused the formation of dendrites. Through the measurement of the primary dendrite spacing (λ1) and the secondary dendrite spacing (λ2), it was concluded that the dendrite structure was obviously refined with the increase in the withdrawal rate to 500 μm/s. The maximum compressive strength reached 1449.8 MPa, and the maximum hardness was 520 HV. Moreover, the plastic strain of the alloy without directional solidification was 2.11%, while the plastic strain of directional solidification was 12.57% at 500 μm/s. It has been proved that directional solidification technology can effectively improve the mechanical properties of the CoCrCuFeNiTi0.8 high-entropy alloy.
Highlights
Conventional alloys are designed by using one or two principle elements and adding other trace elements
The results show that the oxidation resistance of the Al2 CoCrCuFeNi alloy is the best among the five high-entropy alloys (HEAs) [19]
0.8 at the withdrawal rates of 50 μm/s, particles can be observed, which may be caused by the excessive corrosion of Cu
Summary
Conventional alloys are designed by using one or two principle elements and adding other trace elements. Yeh et al calls such alloys high-entropy alloys (HEAs) and proposes new alloy design concepts [2]. These alloys are composed of five or more elements in equal or nearly equal molar proportions. Multi-principle high-entropy alloys have four special effects [3]: high-entropy effect, lattice distortion effect, sluggish diffusion effect, and cocktail effect. The high-entropy effect makes the alloy crystallize into a solid solution rather than intermetallics, and the lattice distortion effect further improves the material properties. A variety of HEAs have been reported, and many excellent properties have been found, such as excellent compression or stretch performance [4,5], good wear performance [6,7], ferromagnetic properties [8], creep resistance [9], biocompatibility [10], deformation behavior [11], and excellent mechanical and magnetic properties [12,13]
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