Dynamic structure evolution and failure mechanism of nanocrystalline AlCo-CrFeNi
The molecular dynamics method was used to simulate the microstructure dynamic evolution,dislocation,and pore motion characteristics of AlCoCrFeNi high-entropy alloy at temperature 300 K and strain rate of 1×109 s-1,and the failure mechanism was revealed.The simulation results show that the maximum load-bearing,longitudinal modulus,and ductility of the nano-polycrystalline AlCoCrFeNi high-entropy alloy are lower than those of nano-monocrystalline.The strain reduction and peak stress reduction of nano-polycrystalline before yield are 25%and the peak stress reduction is 23.8%.The phase transition,dislocation,hole,and failure mechanism of the two nanocrystallines are different during the stretching process.During the stretching process of nano-monocrystals,the FCC structure is mainly transformed into a non-crystalline structure.The atomic position changes after the phase change,accompanied by a large number of Shorkly dislocations,and moves with the growth direction of the non-crystalline structure.The hole nucleation,growth,penetration,and failure fracture of non-crystalline structure area are mainly amorphous perforation fault.During the stretching process of nano-polycrystalline,the FCC structure mainly transforms to HCP structure and non-crystalline structure,and the atomic position changes after the phase change,accompanied by a large number of 1/6<112>(Shortly)dislocations and a small number of 1/6<110>(Stair-rod)dislocations,1/3<100>(Hirth)dislocations,and other dislocations continue to be generated and annihilated.The material undergoes certain plastic deformation,with nucleation of pores in the non-crystalline structure area of the grain boundary,growth and expansion along the grain boundary,and penetration through the grain boundary until failure fracture,showing mainly intergranular fracture.
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