激光诱导击穿光谱对焊缝熔合区的元素成分分布分析

激光诱导击穿光谱(LIBS)是近十几年来快速发展的一种新的表面分析工具，由于具有分析速度快、灵敏度高等优点，故在材料科学领域引起广泛的关注。文中采用LIBS、扫描电子显微镜／能谱仪(SEM/EDS)和电子探针显微分析(EPMA)三种分析方法，对两类不同焊缝的熔合线区域进行线扫描分析，研究了Ni，Mn，C，Si等元素在熔合线区域含量的变化情况。结果表明，对于含量较高且焊缝和母材成分差别较大的Ni和Mn元素，三种方法获得了一致的分析结果，两试样焊缝内的Ni和Mn含量均高于母材，在熔合线区域明显体现出浓度梯度分布。三种方法根据Ni和Mn的浓度分布测得的熔合线区宽度值比较接近。对于含量较低且焊缝和母材成分差别较小的C和Si元素，采用SEM/EDS和EPMA时，焊缝与母材之间的成分差异没有分析出来;而采用LIBS时，两区域的成分差异则可以清晰的展现出来，在熔合区域能够清楚观察到浓度梯度分布曲线。LIBS的分析灵敏度明显高于SEM/EDS和EPMA，在分析低含量元素时更具优势。

Element Distribution Analysis of Welded Fusion Zone by Laser-Induced Breakdown Spectroscopy

Over the past decade there has been intense activity in the study and development of laser-induced breakdown spectroscopy (LIBS). As a new tool for surface microanalysis, it caused widespread in materials science because of the advantage of rapid and high sensitivity. In the present paper, the distribution of Ni, Mn, C and Si near weld fusion line was analyzed on two kinds of weld sample. Line scanning mode analysis was carried out by three different kinds of methods, namely laser-induced breakdown spectroscopy (LIBS), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and electron probe X-ray microanalyser (EPMA). The concentration variation trend of Ni and Mn acquired by LIBS is coincident with SEM/EDS and EPMA. The result shows that the content of Ni and Mn was significantly different between weld seam and base metal on both the samples. The content of Ni and Mn was much higher in weld seam than in base metal, and a sharp concentration gradient was analyzed in the fusion zone. According to the distribution of Ni and Mn, all the three methods got a similar value of welded fusion zone width. The concentration variation trend of C and Si acquired by LIBS is not coincident with SEM/EDS and EPMA. The concentration difference between weld seam and base metal was analyzed by LIBS, but had not by SEM/EDS and EPMA, because of the low concentration and slight difference. The concentration gradient of C and Si in fusion zone was shows clearly by LIBS. For higher sensitivity performance, LIBS is much more adapted to analyze low content element than SEM/EDS and EPMA.