Directional Anisotropy of Crack Propagation Along $Σ$3 Grain Boundary in BCC Fe

Atomistic simulations of twin boundary effect on the crack growth behaviour in BCC Fe

In this paper, the effect of twin boundaries on the crack growth behaviour of single crystal BCC Fe has been investigated using molecular dynamics simulations. The growth of an atomically sharp crack with an orientation of (111)$<$110$>$ (crack plane/crack front) has been studied under mode-I loading at constant strain rate. In order to study the influence of twin boundaries on the crack growth behaviour, single and multiple twin boundaries were introduced perpendicular to crack growth direction. The results indicate that the (111)$<$110$>$ crack in single crystal BCC Fe grows in brittle manne…

Atomistic fracture in bcc iron revealed by active learning of Gaussian approximation potential

The prediction of atomistic fracture mechanisms in body-centred cubic (bcc) iron is essential for understanding its semi-brittle nature. Existing atomistic simulations of the crack-tip deformation mechanisms under mode-I loading based on classical interatomic potentials yield contradicting predictions. To enable fracture prediction with quantum accuracy, we develop a Gaussian approximation potential (GAP) using an active learning strategy by extending a density functional theory (DFT) database of ferromagnetic bcc iron. We apply the active learning algorithm and obtain a Fe GAP model with a ma…

定向干燥过程中有序裂纹阵列的稳定扩展

Stable propagation of an ordered array of cracks during directional drying

我们研究的外观和演变的一个阵列的平行裂纹在薄板的材料是定向干燥，并表明，裂纹均匀地穿透材料，如果干燥前是足够尖锐的。我们还表明，裂纹有一种趋势，成为均匀分布在渗透过程中。裂纹之间的典型距离主要由表面处的图案的典型距离决定，并且在穿透期间不会改变。我们的研究结果与最近的实验工作，并可以扩展到三维描述的性质，在某些地质构造中观察到的柱状多边形图案。

Atomistic simulations on ductile-brittle transition in <111> BCC Fe nanowires

Molecular dynamics simulations have been performed to understand the influence of temperature on the tensile deformation and fracture behavior of $<$111$>$ BCC Fe nanowires. The simulations have been carried out at different temperatures in the range 10-1000 K employing a constant strain rate of $1\times$ $10^8$ $s^{-1}$. The results indicate that at low temperatures (10-375 K), the nanowires yield through the nucleation of a sharp crack and fails in brittle manner. On the other hand, nucleation of multiple 1/2$<$111$>$ dislocations at yielding followed by significant plastic deformation leadi…

Fracture Diodes: Directional asymmetry of fracture toughness

Toughness describes the ability of a material to resist fracture or crack propagation. It is demonstrated here that fracture toughness of a material can be asymmetric, i.e., the resistance of a medium to a crack propagating from right to left can be significantly different from that to a crack propagating from left to right. Such asymmetry is unknown in natural materials, but we show that it can be built into artificial materials through the proper control of microstructure. This paves the way for control of crack paths and direction, where fracture -- when unavoidable -- can be guided through…

体心立方-液体界面晶体各向异性的Ginzburg-Landau理论

Ginzburg-Landau theory of crystalline anisotropy for bcc-liquid interfaces

界面自由能$γ$的弱各向异性是影响具有原子级粗糙固-液界面系统中枝晶生长形态的关键参数。采用Ginzburg-Landau理论研究了体心立方（bcc）形成系统的各向异性的物理起源和定量预测，其中序参量是对应于主倒易晶格矢量的密度波的振幅。我们发现，这个理论预测正确的符号，$γ_{100}>γ_{110}$，和幅度，$(γ_{100}-γ_{110}) / (γ_{100}+γ_{110})\approx 1%$，这种各向异性的MD模拟的结果与Fe。结果表明，固体密度波进入液体的空间衰减率的方向依赖性，由晶体结构施加，是各向异性的主要决定因素。通过对$\{110\}$晶面不同倒易晶格矢量密度波剖面的MD计算，验证了这种方向依赖性。我们的结果与根据Ginzburg-Landau理论[Shih \emph{et al.}，Phys. Rev. A { \bf 35}，2611（1987）]的早期公式预测的逆序$γ_{100}<γ_{110}$进行了对比。