Ni/Ni3Al拉伸力学性能的分子动力学模拟

Molecular Dynamics Simulation of Tensile Mechanical Properties of Ni/Ni3Al

摘要:

采用分子动力学方法研究了Ni/Ni₃Al的拉伸力学性能。首先模拟了在室温、恒定应变速率环境下γ′强化相的含量对Ni/Ni₃Al拉伸力学性能的影响,重点研究了具有三种典型特征的γ′强化相含量下的Ni/Ni₃Al微观组织演化。研究结果表明:相比于单晶Ni,γ′强化相可以提高Ni/Ni₃Al的抗拉强度,这是因为在塑性变形过程中,随着位错的不断增殖,位错密度逐渐增大,导致位错塞积,增大了位错运动的阻力,提高了抗拉强度。接着研究了温度对Ni/Ni₃Al拉伸力学性能的影响,发现Ni/Ni₃Al-10 vol%Ni₃Al的抗拉强度随着温度的升高呈下降趋势。这是因为随着温度的升高,原子内部动能增大,导致原子热运动越剧烈,原子间的结合力越弱,脱离平衡位置的原子来不及回到平衡位置,FCC结构转变为大量的HCP结构和其他无序原子排列结构,导致晶格畸变,降低了抗拉强度。最后研究了应变速率对Ni/Ni₃Al的拉伸力学性能的影响,结果表明,抗拉强度对低应变速率不敏感,对高应变速率敏感。

Abstract:

The tensile mechanical properties of Ni/Ni₃Al are simulated by molecular dynamics. First, the effect of the content of γ′ strengthening phase on the tensile mechanical properties of Ni/Ni₃Al is studied at room temperature and constant strain rate. The microstructure evolution of Ni/Ni₃Al under the content of γ′ strengthening phase with three typical characteristics is especially investigated. Compared with single crystal Ni, it is found that the γ′ strengthening phase can increase the tensile strength of Ni/Ni₃Al. This is because during the plastic deformation process, as the dislocations continue to multiply, the dislocation density gradually increases, resulting in dislocation plugging, which increases the resistance to dislocation movement, thereby increasing the tensile strength. Secondly, temperature effect of the tensile mechanical properties of Ni/Ni₃Al is studied, and it is found that the tensile strength of Ni/Ni₃Al-10 vol%Ni₃Al decreased with increasing temperature. This is because as the temperature increases, the internal kinetic energy of the atom increases, resulting in the more intense thermal motion of the atoms, and the weaker the bonding force between the atoms. The atoms leaving the equilibrium position have no time to return to the equilibrium position, and the FCC structure is transformed into a large number of HCP structures and other atomic arrangements, which cause lattice distortion and reduce tensile strength. Finally, the effect of strain rate on the tensile mechanical properties of Ni/Ni₃Al is studied. The results show that the tensile strength is not sensitive to low strain rate, but sensitive to high strain rate.