  In order to efficiently explore the nearly infinite composition space in
multicomponent solid solution alloys, it is important to establish predictive
design strategies and use computation-aided methods. In the present work, we
demonstrated the density functional theory calculations informed design routes
for realizing transformation-induced plasticity (TRIP) and twinning-induced
plasticity (TWIP) in Cr-Co-Ni medium entropy alloys (MEAs). We systematically
studied the effects of magnetism and chemical composition on the generalized
stacking fault energy surface (gamma-surface) and showed that both chemistry
and the coupled magnetic state strongly affect the gamma-surface, consequently,
the primary deformation modes. Based on the calculated effective energy
barriers for the competing deformation modes, we constructed composition and
magnetism dependent deformation maps at both room and cryogenic temperatures.
Accordingly, we proposed various design routes for achieving desired primary
deformation modes in the ternary Cr-Co-Ni alloys. The deformation mechanisms
predicted by our theoretical models are in nice agreement with available
experimental observations in literature. Furthermore, we fabricated two
non-equiatomic Cr-Co-Ni MEAs possessing the designed TWIP and TRIP effects,
showing excellent combinations of tensile strength and ductility.

Materials Science