Phase and morphological changes of crystalline material during internal cavity fabrication using laser ablation

doi:10.11949/j.issn.0438-1157.20170649

Abstract

Abstract:

The phase and morphological changes of crystalline material during laser internal ablation are studied using molecular dynamics simulations. The atomic images are obtained by recording the velocity and position variation of atoms,stress variation and temperature distribution contour of the materials along the ablation process are charted by statistical physics method and been used to analyze the mechanism of laser ablation. Furthermore,P-T phase diagram are used to study the phase change of the materials in the particular part of the target. The results suggest that only specific laser energy fluence in particular range can induce inside cavity in crystalline material,strong stress wave can be produced during deposition and conversion of laser energy in the target material,and the travel of strong stress wave could lead to separation and explosion of materials in the weld pool and cause structural damage in the depths. Besides,it could be found that the heat affected zone is very small during the laser ablation process by analyzing the temperature distribution contour,and most of the lattice defects caused by the laser energy can recover after the material is cooled,however,there are some scatter schistose defects remained in the crystal lattice.

Key words: pulsed laser, internal cavity, phase change, molecular simulation, microscale

摘要：

采用分子动力学方法对皮秒脉冲激光在晶体材料内部熔蚀出空穴的过程进行了模拟研究。通过记录整个烧蚀过程中粒子速度和位置的变化得到了材料形态变化的原子图像；同时，对粒子动能和受力进行统计分析得到了整个材料内部的应力传导和温度变化分布，并利用P-T相图对特定位置处的材料相态变化进行了分析。结果表明：仅处于特定能量密度范围内的皮秒脉冲激光可在晶体材料内部加工出孔穴；激光能量在烧蚀点处的累积以及转化会导致材料内部出现极强的应力波，并且应力的传递将导致烧蚀点处熔池中材料的喷溅与分离，并使材料内部产生结构缺陷；此外，在分析材料内部的温度分布时可以发现激光烧蚀过程中的热影响区极小，并且大部分在加热过程中被破坏的晶格结构在材料冷却后能得到恢复，但晶体材料中仍会存在分散的片状晶格缺陷。

关键词: 脉冲激光, 内部空穴, 相变, 分子模拟, 微尺度

CLC Number:

TQ026.7

LI Yan, YANG Chao. Phase and morphological changes of crystalline material during internal cavity fabrication using laser ablation[J]. CIESC Journal, 2017, 68(S1): 240-246.

李艳, 杨超. 激光熔蚀内部孔穴形态及相态变化[J]. 化工学报, 2017, 68(S1): 240-246.

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