Chair for Materials Science and Engineering

Grain-size dependence of σ-phase precipitation kinetics in CrMnFeCoNi high-entropy alloys and its effect on mechanical behavior: Aditya Srinivasan Tirunilai’s research is focussed on precipitation kinetics of σ-phase particles in an off-equiatomic variant of the Cantor alloy (Cr-Mn-Fe-Co-Ni). The σ-phase is a topologically close packed phase that is commonly seen in not just multiple high entropy alloys (HEA) but steels and Ni-based super alloy as well. The present research focuses on the effect of grain size on precipitation kinetics in an effort to understand the factors that influence particle characteristics. In turn, variation in these characteristics, including area proportion, morphology, size, nucleation sites, etc., affect the mechanical behavior of the alloy.
The mechanical behavior is therefore investigated after having established a correlation between temperature, time and grain size, and precipitate characteristics. For the sake of statistically relevant information on precipitates, scanning electron microscopy (SEM) will be employed, with more detailed analyses of matrix-precipitate interface and precipitate nuclei investigations carried out via transmission electron microscopy (TEM) and atom probe tomography (APT). The mechanical behavior of the alloy will be investigated in via tensile tests, both ex-situ and in-situ within an SEM. This will not only yield information on strength and ductility, but on fracture mechanics. This is important considering that the ultimate effect of σ-phase in HEA, either positive (strengthening without compromising ductility) or negative (embrittling), is unclear.