Orientation-dependent lattice rotation and phase transformation in an additively manufactured high-entropy alloy

Abstract

• Grain rotation paths are revealed for the first time in a high-entropy alloy. • A new lattice reorientation factor is defined to predict the grain rotation paths. • A new criterion is proposed to identify grains exhibiting FCC→HCP transformation. • The newly defined factors can also be presented in the form of pole figures. • Lattice rotation induced grain coalescence is linked to misorientation angles. The rapidly increasing scientific interest in 3D-printed high-entropy alloys (HEAs) necessitates the understanding of their deformation mechanisms. Here, we present the grain rotation behavior of a nearly equiatomic CrMnFeCoNi HEA fabricated with laser-beam powder bed fusion via quasi in-situ electron backscatter diffraction (EBSD) observations during compressive deformation. The rotation paths of grains can be predicted via a new lattice reorientation factor ( m A ), defined as the average of primary and secondary slip Schmid factors. The grains that initially have their <111> directions oriented close to the loading direction with low-to-intermediate m A values tend to rotate towards the <101> pole. The grains oriented in the center of inverse pole figures with high m A values develop multiple rotation paths pointing away from the <001> pole. The cube-oriented grains with their <001> directions close to the loading direction undergo face-centered cubic (FCC)-to-hexagonal close-packed (HCP) phase transformation due to the activation of octahedral slip involving multiple slip systems. This transformation can be well elucidated via a modified parameter, defined as the average of four maximum Schmid factors on each of four {111} slip/twinning planes in FCC crystals. The findings provide new insights into the underlying mechanisms for deformation-induced grain rotation and phase transformation and help pave the way for developing advanced HEAs via transformation-induced plasticity.