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基于建立的纳秒脉冲激光与金属铝相互作用的二维轴对称模型, 仿真研究了光束整形对纳秒脉冲激光烧蚀金属铝过程中蒸发烧蚀动力学的影响. 结果表明: 等离子体屏蔽对靶材的烧蚀特性具有显著影响, 屏蔽效应主要体现在脉冲的中后期. 对于3种激光轮廓, 高斯光束的屏蔽效果最强, 随着整形后的平顶光束直径的增大, 屏蔽效果逐渐减弱. 平顶光束与高斯光束作用下, 靶材温度的二维空间分布较为不同. 高斯光束作用时, 靶材中心最先升温, 随后温度沿径向和轴向扩散. 由于平顶光束的能量分布更加均匀, 因此一定径向范围内的靶材同时升温. 光束整形对靶材的蒸发烧蚀动力学影响较大. 对于高斯光束, 靶材中心先烧蚀, 随后产生径向烧蚀. 由于整形后平顶光束的能量密度降低, 因此靶面蒸发时间较高斯光束延后, 并且一定径向范围内的靶材同时发生蒸发烧蚀. 3种激光轮廓下, 靶材的蒸发烧蚀形貌与光束的强度分布类似, 其中高斯光束的烧蚀坑呈中间深两边浅的特点, 平顶光束的烧蚀坑较为平坦.Based on the established two-dimensional asymmetric model of the interaction between a nanosecond pulse laser and metallic aluminum, the effect of beam shaping on the evaporation ablation dynamics during the ablation of metallic aluminum by a nanosecond pulse laser is simulated. The results show that plasma shielding, which has a significant influence on the ablation properties of the target, occurs mainly in the middle phase and late phase of the pulse. Among the three laser profiles, the Gaussian beam has the strongest shielding effect. As the diameter of the reshaped flat-top beam increases, the shielding effect gradually weakens. The two-dimensional spatial distribution of target temperature is relatively different between ablation by a Gaussian beam and that by a flat-top beam. For the Gaussian beam, the center of the target is first heated, and then the temperature spreads in radial direction and axial direction. For the flat-top beam, due to the uniform energy distribution, the target is heated within a certain radial range simultaneously. Beam shaping has a great influence on the evaporation ablation dynamics of the target. For the Gaussian beam, the center of the target is first ablated, followed by the radial ablation. For the flat-top beam, the evaporation time of the target surface is delayed due to the lower energy density after the beam has been shaped. In addition, the target evaporates simultaneously in a certain radial range due to the more uniform distribution of laser energy. For each of the three laser profiles, the evaporation morphology of the target resembles the intensity distribution of the laser beam. The crater produced by the Gaussian beam is deep in the center and shallow on both sides, while it becomes relatively flat by the flat-top beam.
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参数 数值 单位 密度
($\rho $)$ \rho = \left\{ {\begin{aligned} &{2700, }&&{T \leqslant {T_{\text{m}}}} \\ & {{\rho _{\text{c}}}\left[ {1 + 0.75\left( {1 - {T / {{T_{\text{c}}}}}} \right) + 3{{\left( {1 - {T / {{T_{\text{c}}}}}} \right)}^{{1/3}}}} \right], }&&{{T_{\text{m}}} < T \leqslant {0}{.8}{T_{\text{c}}}} \\ &{634, }&&{T > {0}{.8}{T_{\text{c}}}} \end{aligned}} \right. $ $ {{{\text{kg}}} \mathord{\left/ {\vphantom {{{\text{kg}}} {{{\text{m}}^{3}}}}} \right. } {{{\text{m}}^{3}}}} $ 电导率
($\sigma $)$ \sigma \left( T \right) = \left\{ {\begin{aligned} &{3.69 \times {{10}^7}, }&&{T \leqslant {T_{\text{m}}}} \\ & {{{{{10}^8}} / {\left( {0.00852 T + 15.32896} \right), }}}&&{{T_{\text{m}}} < T \leqslant {0}{.8}{T_{\text{c}}}} \qquad\qquad \quad \\ &{2.52 \times {{10}^4}, }&&{T > {0}{.8}{T_{\text{c}}}} \end{aligned}} \right. $ $ {{\text{S}} \mathord{\left/ {\vphantom {{\text{S}} {\text{m}}}} \right. } {\text{m}}} $ 热导率
($k$)$ k\left( T \right) = \left\{ {\begin{aligned}& {237, }&&{T \leqslant {T_{\text{m}}}} \\ &{2.44 \times {{10}^{ - 8}}\sigma \left( T \right)T, }&&{T > {T_{\text{m}}}} \qquad\qquad \end{aligned}} \right. $ $ \rm W/(m{\cdot}K)$ 反射率
($R$)$ R = \left\{ {\begin{aligned} &{95{\text{%}} , }&&{T \leqslant {T_{\text{m}}}} \\ &{\frac{{{{\left[ {{n_{\text{R}}}\left( T \right) - 1} \right]}^2} + n_{\text{I}}^{2}\left( T \right)}}{{{{\left[ {{n_{\text{R}}}\left( T \right) + 1} \right]}^2} + n_{\text{I}}^{2}\left( T \right)}}, }&&{{T_{\text{m}}} < T \leqslant {0}{.8}{T_{\text{c}}}} \\ &{{\text{69{\text{%}} , }}}&&{T > {0}{.8}{T_{\text{c}}}} \end{aligned}} \right. $ $1$ 吸收系数
($\alpha $)$ \alpha = \left\{ {\begin{aligned} &{1.5 \times {{10}^8}, }&&{T < {T_{\text{m}}}} \\ & {{{4{\text{π }}} }{n_{\text{I}}}\left( T \right)/{\lambda }, }&&{{T_{\text{m}}} \leqslant T \leqslant {0}{.8}{T_{\text{c}}}} \qquad\qquad\quad\\ & {8.5 \times {{10}^6}, }&&{T > {0}{.8}{T_{\text{c}}}} \end{aligned}} \right. $ ${{\text{m}}^{{{ - 1}}}}$ 注: ${n_{\text{R}}}$和${n_{\text{I}}}$分别代表折射率的实部和虚部. 
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参数 符号 数值 单位 固相线温度 ${T_{\text{s}}}$ 936.15 K 液相线温度 ${T_{\text{l}}}$ 939.15 K 熔点 ${T_{\text{m}}}$ 933 K 沸点 ${T_{\text{v}}}$ 2793 K 临界温度 ${T_{\text{c}}}$ 6700 K 临界密度 ${\rho _{\text{c}}}$ 634 ${{{\text{kg}}} / {{{\text{m}}^{3}}}}$ 固相恒压热容 ${C_{{\text{ps}}}}$ 917 $ {{\text{J}} / ( {{\text{kg}} \cdot {\text{K}}})} $ 液相恒压热容 ${C_{{\text{pl}}}}$ 1080 $ {{\text{J}} /{\left( {{\text{kg}} \cdot {\text{K}}} \right)}} $ 融化潜热 ${L_{\text{m}}}$ $ 3.69 \times {10^{5}} $ $ {{\text{J}} /{{\text{kg}}}} $ 蒸发潜热 ${L_{\text{v}}}$ $ {1}{.05} \times {10^{7}} $ $ {{\text{J}} /{{\text{kg}}}} $ 下载:
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