Tuning the Microstructure and Mechanical Properties of Al-Co-Cr-Fe-Ni-Ti Compositionally Complex Alloys Manufactured by Means of L-DED

Abstract

In the current study, a combinatorial high-throughput screening approach based on CALPHAD simulations and experimental validation has been utilized to explore a Co₂CrFeNi₂-Al-Ti CCA-system. This technique, introduced by Kaspar et al. (High Entropy Alloys Mater. https://doi.org/10.1007/s44210-023-00023-x), allows to perform an accelerated alloy development within a wide compositional range and automated fabrication of graded components with varying chemical composition and microstructure. Extended by semi-automated analytical characterization of the produced samples, this approach enables to design novel compositionally complex alloys (CCAs) with promising properties for specific requirements. In our current work, a multiphase design of L1₂ γ′-strengthened Co₂CrFeNi₂-Al-Ti CCAs partially tolerating the disordered BCC-A2 or ordered B2 phases in the alloy microstructure has been utilized. The samples with three different chemical compositions were manufactured by means of laser directed energy deposition (L-DED). By subsequent two-step heat treatment, different phase compositions and microstructures have been realized with a main objective to achieve a high volume fraction of L1₂ γ′ precipitations. Mechanical properties of investigated alloys were characterized by means of tensile tests. Depending on chemical and phase composition of the alloys, the ultimate tensile strength varied in the range of 1060-1150 MPa. The formation of BCC-B2 phase led to decreased yield to tensile strength and showed a detrimental effect on ductility of investigated alloys.