First Principles Study Of The Mechanical Properties Of High-entropy Alloys Al_xCoCrFeNi(x=1,2)

Last century, traditional alloy was widely studied, and difficult to create new alloy system. High-entropy alloys, which have more than five elements with each atom fraction among 5%～35%, have broken the conception of basing on one or two alloys. Attributed to the entropy effect, mixing of high alloys will form BCC, FCC and HCP structures with superior characters, such as high hardness, corrosion stability, withstand high temperature, wear-resisting and so on, which focus the interest of scientists.In this paper, we study the lattice constant, cubic crystal elastic constant (C11,C12, C44) and mechanics elastic modulus of AlCoCrFeNi and Al2CoCrFeNi with first principle method. Results show that a(Al1)<a(Al2) and E(Al)=135.28GPa, which agree well with the experimental value E0=127GPa. G/B (Al1)=0.3745<G/B (Al2)= 0.407575, in accordance with C12-C44(Al1)=50.9GPa>C12-C44(Al2)=48.44GPa, indicates that AlCoCrFeNi has good extensibility, while Al2CoCrFeNi has good brittleness. E(Al1)< E(A12), G(Al1)<G(Al2) and C44(Al2)> C44(Al1) imply that Al2CoCrFeNi has higher hardness than AlCoCrFeNi, which comply well with the experiment.