Twinned dendrites in CrB-structured intermetallic NiGd

Abstract

The formation of twinned dendrites was investigated in orthorhombic CrB-structured NiGd. A NiGd droplet embedded in borosilicate glass-flux was processed by differential scanning calorimetry. A small undercooling of ≈ 20 °C was reached and a cross-section of the solidified sample was analyzed with EBSD. A twinned dendrite is found, that exhibits a twin boundary in its center, both parts sharing a direction and a misorientation angle of 40° between its two parts. The present findings are in agreement with model predictions for CrB-structured alloy solidification based on the investigation of deeply undercooled and homogeneously nucleating NiZr. The present investigation on NiGd serves as a first important step to validate the model's predictions. Due to the observation of twinned dendrites at small undercoolings, the present study may further serve as a first-step to extend the model to heterogeneous growth regimes.