论文标题
分子动力学在纳米级处的Inconel-718的变形机制
Deformation mechanisms of Inconel-718 at nanoscale by molecular dynamics
论文作者
论文摘要
基于Ni的Superaly Inconel-718在金属3D打印中无处不在，那里存在高冷却速率和热梯度。这些制造条件有利于材料中高初始位错密度和孔隙率或空隙。这项工作提出了一种分子动力学（MD）分析方法，可以使用嵌入式原子方法（EAM）电位检查inconel-718中材料特性和失败机制的脱位，冷却速率，空隙及其相互作用的作用。在整个工作中都使用了三种不同的结构：纳米线（NW），纳米木和纳米板。最初，应变速率从10^8S^-1到10^10S^-1分别保持NW直径和温度的恒定在3.17 nm和300K处。通过施加109 s^-1的恒定应变速率，而温度从100k到700K，则将压缩负荷应用于7.04 nm纳米柱。从0.5x10^10 k/s到1 x 10^14 k/s的不同冷却速率应用于纳米板（带有和不带中央空隙）。中央空隙的大小保持固定为2.12 nm。张力的应变速率不仅会导致应变硬化，还会增加脱位密度。我们的计算方法成功地捕获了{111}剪切平面上的大量滑动，这导致由于脱位而裂缝前的合金颈部明显。高冷却速率产生非平衡结构会导致高强度和延性行为。另一方面，较低的冷却速率形成良好的晶体结构会导致低强度和脆性行为。仅由于冷却速率观察到这种脆性到延性过渡。冷却速率可以通过在凝结过程中愈合结构来降低空隙。随后通过不同温度和大小的机械性能详细介绍。
Ni-based superalloy Inconel-718 is ubiquitous in metal 3D printing where high cooling rate and thermal gradient are present. These manufacturing conditions are conducive to high initial dislocation density and porosity or void in the material. This work proposes a molecular dynamics (MD) analysis method that can examine the role of dislocations, cooling rates, void, and their interactions governing the material properties and failure mechanism in Inconel-718 using Embedded Atom Method (EAM) potential. Three different structures: nanowire (NW), nanopillar, and nanoplate are used throughout this work. Initially, strain rates are varied from 10^8s^-1 to 10^10s^-1 keeping the NW diameter and temperature constant at 3.17 nm and 300K respectively. Compressive loading is applied to a 7.04 nm nanopillar by applying a constant strain rate of 109 s^-1 while temperature is varied from 100K to 700K. Different cooling rates ranging from 0.5x10^10 K/s to 1 x 10^14 K/s are applied to nanoplates (with and without a central void). The size of the central void is kept fixed at 2.12 nm. Increasing strain rates in tension not only results in strain hardening but also increase in dislocation density. Our computational method is successful to capture extensive sliding on {111} shear plane, which leads to significant necking of the alloy before fracture due to dislocation. The high cooling rates creating non-equilibrium structure leads to high strength and ductile behavior. On the other hand, the low cooling rate forming well defined crystalline structure causes low strength and brittle behavior. This brittle to ductile transition is observed solely due to cooling rate. Cooling rate may diminish the void by healing the structure during solidifications process. Subsequent mechanical properties by varying temperature and size are also presented in detail.
