The phase formation, dendrite growth kinetics and spontaneous grain refinement in a novel D0₃-type undercooled FeCoNiGe multi-principal element intermetallic

Though considerable efforts have been dedicated to multi-principal-element alloy design, the comprehension of their solidification characteristics remains limited. In this work, a FeCoNiGe multi-principal element intermetallic (MPEI) with D0₃ (∼99.4 vol.%) and trace L1₂ phase was prepared via undercooled rapid solidification. Using ab initio analysis, we find the retention of high-temperature stable D0₃ phase is due to sluggish diffusion, which strongly inhibits the D0₃→L1₂ phase transformation. During the undercooled solidification process of D0₃ phase, disorder trapping has been investigated in situ at an intermediate undercooling of 123 K. In addition, the particular role of sub-grains evolution in spontaneous grain refinement of this FeCoNiGe was uncovered employing a EBSD analysis.