纳米孪晶与Fe掺杂对SLM-Al力学性能影响的分子动力学模拟

Molecular dynamics simulation on effect of nano-twin and Fe doping on mechanical properties of SLM-Al

摘要:

本文通过分子动力学方法研究了不同晶态、孪晶界间距以及Fe掺杂对选区激光熔化(selective laser melting, SLM)铝力学性能的影响。结果表明，纳米孪晶对不同晶态以及是否掺杂了Fe元素的铝的强化效果具有较大的差异。在不同晶态铝中插入纳米孪晶，可以提高单晶铝的抗拉强度，但降低了等轴晶和柱状晶铝的抗拉强度。其中，柱状晶的力学性能对孪晶最敏感，抗拉强度受到影响程度最大。孪晶界间距(λ)对柱状晶铝强度的影响存在临界值(2.8 nm)，当λ小于2.8 nm时，柱状孪晶铝的抗拉强度随着λ增加而减小，当λ大于2.8 nm时，柱状孪晶铝的抗拉强度随着λ增加而逐渐增加，直到接近无孪晶柱状铝的强度。与不同晶态孪晶铝的强度相比，掺杂5 at.% Fe的不同晶态孪晶铝的强度更大，且柱状孪晶Al-5%Fe的强化效果最好，表明合理控制Fe含量和纳米孪晶形态，有望改善SLM铝的力学性能。

Abstract:

The effects of crystalline states, twin boundary spacing, and Fe doping on the mechanical properties of SLM aluminum are examined by performing molecular dynamics simulations of uniaxial tensile tests. The results show that the strengthening effect of twins on aluminum with different crystalline states and whether or not Fe is quite different. Inserting nano-twin in different crystalline aluminum can increase the tensile strength of single crystal aluminum, but reduce the tensile strength of equiaxed grains and columnar grains aluminum. Among them, the mechanical properties of columnar grains are the most sensitive to twins, especially the tensile strength. There is a critical value of 2.8 nm for the effect of twin boundary distance λ on the tensile strength of the columnar crystal aluminum. When λ is less than this value, the tensile strength of columnar twin aluminum decreases with the increase of λ, while when λ is greater than this value, the tensile strength of columnar grains aluminum gradually increases with the increase of λ, until it is close to that of columnar grains aluminum with twin-free. Compared with the tensile strength of different crystalline twin Al, the tensile strength of different crystalline twin Al doped with 5 at.% Fe is greater, and the strengthening effect of columnar twin Al-5%Fe is the best, indicating that reasonable control of the content of Fe and nanotwinned crystalline, which are expected to improve the mechanical properties of SLM aluminum.