High-throughput microstructure characterization of compositionally graded Cr-Nb-Ti-Zr complex concentrated alloys (CCA) prepared by laser directed energy deposition

Abstract

Systematic variation of chemical compositions in quaternary Cr-Nb-Ti-Zr based complex concentrated alloys was achieved through the additive manufacturing technique of laser directed energy deposition (L-DED). Two separate feeders containing binary equimolar mixtures of elemental powders (CrNb/TiZr and CrZr/TiNb) were used simultaneously for deposition of gradient samples on thermally insulated substrate plate. The compositions ranging from approx. 5 to approx. 45 at. % for each element were obtained in the deposited samples. Investigation of the chemical composition effects on the phase content after homogenization heat treatment at 1200 degrees C, within one individual sample, was performed using microhardness measurements, XRD and EDS techniques and microstructural observations by SEM. Cr-Nb-Ti-Zr single-phase/multi-phase regions in the studied quaternary phase diagram were determined. Multi-phase regions contain Cr-rich BCC Laves type phase of varying composition as determined by the chemical composition of the matrix. The presence of the BCC Laves type phase in multi-phase areas was confirmed by CALPHAD simulations. The L-DED technique was found to be capable of producing compositionally graded complex concentrated alloys on the basis of refractory elemental powders with high melting temperatures for the high-throughput microstructure characterization.