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

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 °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.