EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In this contribution the AlxTiyCoCrFeNi alloy system is explored thoroughly over a wide compositional range of x = 0 to 1. (0 to 17 at% Al) and of y = 0 to 0.7 (0 to 10 at% Ti). For this alloy system compositional gradient structures were produced by laser metal deposition of pre-alloyed CoCrFeNi and elemental Al and Ti powders using an in-house developed coaxial cladding system COAXpowerline.
The evolution of the microstructure with increasing Al and/or Ti content was analyzed in the as built as well as the homogenized condition (1350 K for 20 h). Metallographic cross sections were prepared and thoroughly analyzed by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, and electronbackscattered diffraction. Additionally, the evolu-tion of the sample hardness with increasing Al and Ti contents was determined for both sam-ple conditions. In the AlxTiyCoCrFeNi alloy system the lattice structure as well as the sample hardness can easily be adjusted by the variation of Al and Ti content. Both with increasing Al and Ti content a phase transition from a solid solution fcc phase toward a multiphase bcc mi-crostructure consisting of a Fe and Cr rich solidsolution bcc phase and an ordered Al and Ni rich bcc B2 phase can be observed. Thisis combined with an increase in sample hardness from around 200 HV up to around 700 HV in the as built condition. The compositional regions of the phase transitions for both sample conditions were compared to ab initio thermodynamic calcu-lations done using a CALPHAD approach. For the as built condition a strong deviation from the calculated transition regime could be observed. After homogenization the experimental and calculated data are in better agreement.