Abstract Understanding plasticity and strength of high entropy alloys of
HfNbTaTiZr is extremely significant in building nuclear reactors, gas turbines,
aerospace deivces etc. Here we study an equiatomic (Hf 0.20 -Nb 0.20 -Ta 0.20 -Ti 0.2 -Zr 0.20 )
and a non-equiatomic (Hf 0.35 -Nb 0.20 -Ta 0.15 -Ti 0.15 -Zr 0.15 ) mixture of two alloys under
uniaxial tensile loading from molecular dynamics simulations. Modified Embedded
atom potential is used to model both these bcc alloys and all simulations are performed
at 300 K with three different tensile strain rates - 0.0002, 0.0005 and 0.001 ps −1 . Radial
distribution functions, bond-orientational parameters and OVITO are used to analyse
the MD trajectories. At 0.001 ps −1 strain, both these alloys deform similarly, but
differences are observed at 0.0005 and 0.0002 ps −1 strains. At these rates, both alloys
deform elastically till 3%, thereafter they deform plastically till 15-20% strain. Yield
strengths are comparable in the elastic limit but in the plastic limit non-equiatomic
alloy have higher strength. In equiatomic alloy, bcc phase transforms to fcc whereas
in non-equiatomic alloy bcc phase transforms to both fcc and hcp. Formation of
hcp atoms (50%) decrease the plasticity of the non-equiatomic alloy but increases its
strength. We also observe that in both these alloys and at all strain rates, bcc atoms
transform to fcc/hcp atoms through an intermediate amorphous like state. Local
coordination and orientation of all atom change similarly in equiatomic mixture. But in
non-equiatomic mixture local orientation in Hf, Ti and Zr changes differently compared
to Nb and Ta.