The crystal structure types of FeAl

x

NiCrMn high entropy alloy were analyzed by the solid solution characteristic parameters and the first principle

and the effects of Al content on the crystal structure and mechanical properties of FeAl

x

NiCrMn high-entropy alloy was investigated.From the aspects of calculation of solid solution characteristic parameters

energy analysis

and stability criterion of material mechanics

it is found that FeAl

x

NiCrMn（x=0

0.25

0.5

0.75

1）high-entropy alloy mainly exists in a single face-centered cubic solid solution structure.The results reveal that the lattice constant of FeAl

x

NiCrMn alloy is gradually increased with Al content increase

and the melting point and hardness of the alloy is first increased and then decreased.When x=0.75

the elastic modulus and shear modulus of the alloy will be more than those of other FeAl

x

NiCrMn alloys（x=0

0.25

0.5

1）.When x=0.25

the bulk modulus of the alloy reaches the maximum value.Meanwhile

the plasticity of FeAl

x

NiCrMn alloy is decreased gradually with increasing in Al content.The molar content of 0.5 is not only the critical value for the alloy to change from toughness to brittleness

but also from elastic anisotropy to elastic isotropy.