Mechanism for the Improvement of the Mechanical Properties of FeCoCrNi+FeCoCrNiAl-Laminated HEA Fabricated by Laser Melting Deposition
FeCoCrNi+FeCoCrNiAl-laminated high-entropy alloy (HEA) was manufactured by laser melting deposition. The two adjacent HEA layers consisted of columnar grains with the orientation <001>//BD (building direction). However, the grains in the FeCoCrNiAl HEA were smaller than those in the FeCoCrNi HEA. The microstructure of the deposited HEA was dominated by the FCC phase, together with a low content of the BCC phase. After tensile tests, the number of columnar grains with the <011>//BD orientation increased appreciably. The difference in grain size, orientation of grain growth, physical properties of the two-phase structure, and the macroscopic interface between the adjacent HEAs gave rise to the concentration of dislocations and hindered plastic deformation during the tensile testing. As a result, the strength and toughness of the laminated HEA were effectively improved. However, the existence of columnar grains in the laminated HEA initiates and propagates cracking in the weak regions near the grain boundaries under tensile forces.
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