MD simulation.zip from Shear-induced amorphization of pure niobium during nano-cutting

The amorphization of pure metallic materials remains one of the key unresolved challenges in materials science. In this study, we investigate the amorphization mechanism in a typical pure metal with body-centred cubic (BCC) lattice—niobium (Nb)—under nano-cutting conditions. A sharp single-crystal diamond tool was used to perform the nano-cutting process. Pre-machining microstructural analysis revealed that the niobium exhibited a coarse-grained structure, with grain sizes exceeding 10 µm. Post-processing, a gradient microstructure was observed, featuring grain sizes in the order of hundreds of nanometres. Significantly, amorphous cluster structures were identified both within the bulk and on the surface of the processed material, with the amorphous fraction of niobium atoms estimated at approximately 0.25% and 0.31%, respectively. To elucidate the underlying deformation and amorphization mechanisms, molecular dynamics (MD) simulations were carried out. Theoretical results demonstrate that the nano-cutting process generates extremely high shear strain, predominantly inducing plastic deformation along the close-packed {110} crystal planes. This shear-dominated deformation ultimately leads to the formation of amorphous regions in pure niobium. Our findings present a novel experimental and computational approach to understanding shear-induced amorphization in monometallic systems, providing new insights into the structural evolution and deformation pathways of BCC metals under extreme mechanical loading.纯金属材料的非晶化始终是材料科学领域尚未攻克的核心挑战之一。本研究针对具有体心立方（body-centred cubic, BCC）晶格的典型纯金属铌（niobium, Nb），探究其在纳米切削条件下的非晶化机制。实验采用锋利的单晶金刚石刀具开展纳米切削加工。加工前的微观结构分析显示，该铌材呈现粗晶组织，晶粒尺寸超过10 µm。加工后则观测到梯度微观结构，其晶粒尺寸处于百纳米量级。值得注意的是，在加工后材料的本体与表面均识别出非晶团簇结构，铌原子的非晶占比分别约为0.25%与0.31%。为阐明潜在的变形与非晶化机制，本研究开展了分子动力学（molecular dynamics, MD）模拟。模拟结果表明，纳米切削过程会产生极高的剪切应变，主要沿密排{110}晶面引发塑性变形。这种以剪切为主导的变形最终促使纯铌中形成非晶区域。本研究的发现为理解单金属体系中剪切诱导非晶化提供了全新的实验与计算范式，同时为体心立方金属在极端机械载荷下的结构演化与变形路径提供了新的科学洞察。