Al含量和加载速度对Al_(x)CoCrFeNi高熵合金的影响及分子动力学仿真

Influence of Al content and loading speed on Al_(x)CoCrFeNi high entropy alloy and molecular dynamics simulation

通过分子动力学(MD)仿真从硬度、Von Mises应力、剪切应变、位错和相变方面研究了纳米压痕过程中Al含量和加载速度对Al_(x)CoCrFeNi高熵合金(HEA)力学性能的影响。研究结果表明Al含量较少时,HEA内部形成原子剪切带较多,总位错长度和位错密度较大。加载速度较大时大量位错缠结产生高密度的位错胞,阻碍位错滑移,带来显著的强化效应。Al含量与硬度成反比,而加载速度与材料的硬度成正比。此外,在纳米压痕初期,所有HEA发生可恢复的弹性变形。压痕深度增加,材料开始发生塑性变形,位错形核生长。由于压头力的作用,材料内部原子重新排列,FCC结构逐渐转变为BCC结构,HCP结构和无序结构。与压头相接触的区域原子应变较高并且率先转变为无序结构。经过多次加载-卸载循环,弹性变形逐渐转变为塑性变形,合金中残留的应力变多,Al_(x)CoCrFeNi HEA表现出明显的循环劣化现象。

The effects of Al content and loading speed on the mechanical properties of Al_(x)CoCrFeNi high entropy alloy(HEA)during nanoindentation were studied by molecular dynamics(MD)simulation from hardness,Von Mises stress,shear strain,dislocation,and phase transformation.The results show that when the Al content is lower,more atomic shear bands are formed in HEA,and the total dislocation length and density are more significant.When the loading speed is high,many dislocation tangles produce high-density dislocation cells,which hinder dislocation slip and bring a considerable strengthening effect.Al content is inversely proportional to hardness while loading speed is directly proportional to the hardness of materials.In addition,at the initial stage of nanoindentation,all HEAs undergo recoverable elastic deformation.The material experiences plastic deformation,dislocation nucleation,and growth with increased indentation depth.Due to the indenter force,the atoms in the material are rearranged,and the FCC structure gradually transforms into BCC,HCP,and disordered structures.The atomic strain in the region in contact with the indenter is high and is the first to transform into a disordered structure.After many loading-unloading cycles,the elastic deformation gradually changes into plastic deformation,the residual stress in the alloy increases,and Al_(x)CoCrFeNi HEA exhibits an evident cyclic degradation phenomenon.