Effect of Microstructure, Strain Rate, and Elevated Temperature on the Compression Property of Fe-Co-Ni-Cr-Zr Alloy

Eutectic high-entropy alloys with FCC solid solution phase and hard Laves phase can be used as potential structural materials to meet the service conditions from room temperature to elevated temperature. In this work, a series of FeCoNiCrZr0.5 alloy rods with different diameters (phi 2, phi 3, and phi 5 mm) prepared by vacuum suction casting were applied to investigate the effects of microstructure and strain rate on compression properties at room temperature, as well as the microstructure evolution and deformation behavior at high temperature. With the decrease of the sample diameter, in addition to the significant refinement of the lamellar eutectic in the solidified microstructure, the alloy also undergoes a transformation from regular eutectic to dendritic Laves phase plus eutectic microstructure. Moreover, the deformation behavior of the alloy at different strain rates was discussed based on the cross-sectional microstructure and fracture-surface morphology of the compressed samples. The alloy samples obtained the maximum compressive strengths of 2173 MPa at the strain rate of 10(-4)/s. Also, the instability of the lamellar eutectic and the precipitation of Ni10Zr7 phase occurred in the alloy sample after annealing above 1073 K. Finally, combined with finite element simulation and microscopic transmission analysis, it is proved that the inhomogeneous microstructure of the deformed alloy under high-temperature compression consists of the deformation region of bending lamellar or shear instability and the spheroidized recrystallization region. This alloy exhibits excellent high-temperature performance due to the coordinated fine microstructure and the large number of stacking faults present in the deformation. In summary, this work will provide new insights and guidance for the design and application of gradient microstructure with dual-phase and structural high-entropy alloys.