Combinatorial Alloy Design and Microstructure Evolution in Laser-cladded Al-Co-Cr-Fe-Ni-Ti Compositionally Complex Alloys

In this work, we propose a strategy for high-throughput design and development of compositionally complex alloys combining theoretical and experimental alloy screening. This methodology was applied for the exploration of the (Co2CrFeNi2)1-x-yTixAly subsystem of so-called high entropy superalloys in the Al-Co-Cr-Fe-Ni-Ti alloy system. Alloy design was guided by thermodynamic calculations based on the CALPHAD approach. The evolution of the microstructure with increasing Al and Ti content was analyzed in the as-built, homogenized and age-hardened conditions by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and electron backscattered diffraction. Additionally, the evolution of the sample hardness with increasing Al and Ti contents was determined for all conditions. Based on the experimental results, the reliability of the CALPHAD calculations was assessed. Generally, a good agreement between calculations and experiments is achieved in the homogenized state. In the aged conditions, the CALPHAD predictions of the precipitation processes are partly inaccurate and need improvement. Optimal Al and Ti concentrations are derived for age hardening through L12 and combined L12 + B2 precipitations.