Energy feedthrough and microstructure evolution during direct laser peening of aluminum in femtosecond and picosecond regimes
Energy feedthrough and microstructure evolution during direct laser peening of aluminum in femtosecond and picosecond regimes
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DOI：
10.1063/5.0052510
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发表时间：
2021-07-07
影响因子：
3.2
通讯作者：
Kermouche, G.
中科院分区：
文献类型：
--
作者：
Nakhoul, A.;Rudenko, A.;Kermouche, G.
最近，超快激光被用于在处理之前不使用牺牲层的情况下对铝基合金2024-T351的表面完整性进行改性和表面区域进行喷丸。我们表明，可控的激光参数，如能量密度和脉冲持续时间有显着的影响，喷丸质量，如压缩残余应力，硬度和表面粗糙度的喷丸零件。通过X射线衍射分析了残余应力分布。通过控制激光能量密度和脉冲持续时间，有可能获得200 MPa的压缩残余应力接近表面和100 MPa的压缩残余应力在50 μ m的深度。此外，在近表面区域的显微硬度从2.1增加到2.5 GPa。此外，位错密度从高分辨率的X射线衍射峰进行了评估。位错密度的增加表明发生了塑性变形，产生了残余压应力和硬度的提高。塑性变形被认为是由超快激光诱导的压力波。激光参数和改性表面性能之间的相关性解释的激光激发，材料松弛，和压力波之间的复杂的相互作用。皮秒范围内的脉冲持续时间和相对低的能量密度可能是具有小表面粗糙度的最佳喷丸质量的最佳条件，这可能用于减少增材制造部件的表面开裂和相关故障。
Ultrafast laser was recently used to modify the surface integrity and peen the surface region of aluminum based alloy 2024-T351 without a sacrificial layer prior to the process. We show that controllable laser parameters such as fluence and pulse duration have a significant influence on peening qualities, such as the compressive residual stress, hardness, and surface roughness of peened parts. The residual stress profile was analyzed by x-ray diffraction. By controlling the laser fluence and pulse duration, it was possible to obtain 200 MPa of compressive residual stresses close to the surface and 100 MPa of compressive residual stresses at 50 mu m depth. Moreover, micro-hardness was increased from 2.1 to 2.5 GPa in the near-surface region. In addition, the dislocation densities were evaluated from high-resolution x-ray diffraction peaks. The increase of the dislocation density indicates that plastic deformation occurred, which generated compressive residual stresses and hardness enhancement. Plastic deformation is considered to be created by an ultrafast laser-induced pressure wave. The correlation between laser parameters and modified surface properties is interpreted by the complex interplay between laser excitation, material relaxation, and pressure waves. A pulse duration in the picosecond range and a relatively low fluence is possibly the optimal condition for a best peening quality with small surface roughness, which could potentially be used to reduce surface cracking and associated failures of additively manufactured parts.