Microstructure, tensile property and forming performance of FeCoNi2Al medium entropy intermetallic fabricated by investment casting

Abstract

To further promote the industrial application of medium/high entropy intermetallics, a bulk of FeCoNi2Al medium entropy intermetallic ingot with 16 kg as the research object was prepared in this study. Microstructure and mechanical properties of the as-cast alloy were studied and analyzed in detail. Moreover, characteristic structural components were obtained via investment casting route, by which the forming performance of the alloy was evaluated. Results show that the FeCoNi2Al medium entropy intermetallic ingot has good composition uniformity. The as-cast alloy is composed of B2 primary phase with dendritic morphology and interdendritic L12+B2 phase eutectic structure with lamellar morphology. The tensile strength of the as-cast alloy is 1115 MPa at room temperature, and the elongation is 4.6%. At 650 ℃, the tensile strength of the as-cast alloy is 434 MPa, and the elongation can reach 14.6%. Melt fluidity of the FeCoNi2Al medium entropy intermetallic is lower than that of TC4 alloy but better than that of TiAl-4822 alloy. When the thickness of the characteristic structural component is 2 mm, the plate casting is incompletely filled and a mass of shrinkage porosity is formed within the casting. Moreover, the cessation mechanism of flow for the molten alloy is due to the accumulation of solid particles at the tip of flow. Results of this research will lay a certain technical foundation for the casting process optimization and industrial application of medium/high entropy intermetallics.

Keywords

• medium/high entropy alloy
• intermetallic
• investment casting
• eutectic microstructure
• mechanical property