LIBS对钛合金焊缝中成分的原位统计分布分析表征

钛合金凭借其强度高、耐蚀性好、耐热性高等特点已经被广泛应用于航天、海洋、生物医药等诸多领域，其中Ti-6Al-4V（TC4）合金的耐热性、强度、塑性、韧性、成形性、可焊性、耐蚀性和生物相容性均较好，已成为钛合金工业中的王牌合金。钛合金在激光焊接时，加入表面活性剂可以增加焊缝熔深、提高焊接效率、改善焊缝微观组织的不均匀性，但是可能会改变熔合区和焊缝区中元素含量及其分布状态，从而可能会对材料的性能产生一定的影响。运用LIBS分析技术对TC4钛合金焊接试样表面进行面扫描同步获得多元素成分信息，同时结合原位统计分布分析方法（OPA），实现了对钛合金母材、熔合区、焊缝成分及其分布状态的快速表征，为活性剂的选择和焊接后钛合金的材料性能提供一种新的评价手段。选取了两个使用不同活性剂进行焊接的TC4钛合金薄板试样，选取焊缝纵切面方向作为分析面，采用320目的氧化铝砂纸进行表面处理，利用LIBSOPA系统进行成分分布统计表征。首先，对激发光斑和剥蚀条件进行条件优化，最终选择200 μm的激发光斑、10个预剥蚀脉冲10个剥蚀脉冲进行实验，并建立了钛合金中C，Al，V，Fe，Si和Ti六个元素的校准曲线（其中Si元素主要来自活性剂）；然后对钛合金焊接样品进行了区域扫描，并对元素含量和分布状态进行了统计表征。同时，在钛合金焊接样品的不同部位进行分区取样，采用高频红外法分析C元素含量，并与LIBSOPA结果进行比对，两种测试方法结果吻合。元素Al，V，Fe，Si和Ti分布结果与微束X荧光光谱法对应性较好。运用LIBSOPA 技术实现了对钛合金母材、熔合区、焊缝中多元素的成分分布表征，为快速判定钛合金焊缝中成分及分布状态提供了全新的评价表征手段。

Original Position Statistic Distribution Analysis （OPA） and Characterization of Components in Titanium Alloy Welding Sample by Laser Induced Breakdown Spectroscopy （LIBS）

Titanium alloys have been used in many fields such as aerospace, marine, biomedicine, etc. due to their high strength, good corrosion resistance, and high heat resistance. Due to the heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biological phase of Ti-6Al-4V (TC4) alloy. It has become the best alloy in the titanium alloy industry. When titanium alloy is welded by laser, when a surfactant is added, weld penetration can be increased, welding efficiency is improved, and the unevenness of the weld microstructure is improved, but the content and distribution of elements in the fusion zone and weld zone may be changed. So the performance of the material may be affected. In this paper, laser-induced breakdown spectroscopy (LIBS) analysis technology is used to scan the surface of TC4 titanium alloy welding specimens to obtain multi-element composition information simultaneously. At the same time, combined with the original position statistic distribution analysis method (OPA), the composition and its distribution state of base material, fusion zone, weld composition of titanium alloy can be quickly characterized, and a new evaluation method will be provided for the selection of the active agent and the material properties of titanium alloy after welding. In this paper, two different active agents are selected to weld the TC4 titanium alloy sheet. The longitudinal section of the weld is used as the analysis surface, 320 mesh alumina sandpaper is used for surface treatment LIBSOPA system is used for composition distribution analysis. Firstly, the condition optimization experiment was carried out on the excitation spot and ablation conditions. Finally, the 200 μm excitation spot, 10 pre-ablation pulses and 10 ablation pulses were selected for the experiment; secondly, the calibration curves of C,Al, V, Fe, Si, Ti six elements were established (Si element mainly comes from the active agent), and then the area scanning of the titanium alloy welding samples was finished, and the element content and distribution state were characterized. Samples were taken from different parts of the titanium alloy welding samples, and the high-frequency infrared method was used to analyze the C element content, which verified the correctness of the LIBSOPA technology analysis C results. The distribution results of the elements Al, V, Fe, Si and Ti correspond to the microbeam X-ray fluorescence spectrometry. In this paper, LIBSOPA technology is used to characterize the composition distribution of multiple elements in the titanium alloy base metal, fusion zone and weld, which provides a new evaluation and characterization method for quickly determining the composition and distribution status titanium alloy weld.