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为研究合金在连续激光辐照过程中反射率变化机理,建立了积分球反射率测量装置,测量了1.06μm连续激光辐照过程中45号钢反射率变化。实验结果表明,激光辐照过程中反射率先快速下降,然后产生周期波动。随着激光功率增大,反射率开始下降点和最小值点对应温度逐渐升高,极大值个数增多。建立了多层氧化膜影响模型,结合氧化膜生长规律,分析了不同结构、不同厚度变化规律氧化膜层的反射率特征,实验结果验证了理论模型的合理性。结果表明,反射率变化主要原因是氧化膜生长引起的多光束干涉与吸收效应。由FeO-Fe3O4-Fe2O3组成的三层氧化膜中,中间吸收型Fe3O4膜是反射率变化的主要影响因素,最外层Fe2O3膜引起的干涉效应影响反射率的稳定值,最内层FeO膜的贡献可以忽略。
In order to study the mechanism of reflectivity changes during continuous laser irradiation, an integrating sphere reflectance measuring device was set up to measure the reflectivity of No.4 steel during 1.06μm continuous laser irradiation. The experimental results show that the reflectivity decreases sharply during the laser irradiation and then produces periodic fluctuations. With the increase of the laser power, the temperature at which the reflectance starts to decrease and the minimum corresponds to a gradual increase in temperature and the number of maximums increase. The multi-layer oxide film influence model was established. Combined with the growth law of oxide film, the reflectivity characteristics of oxide film with different structure and thickness were analyzed. The experimental results verify the rationality of the theoretical model. The results show that the main reason for the change of reflectance is the multi-beam interference and absorption effect caused by oxide film growth. Of the three oxide films composed of FeO-Fe3O4-Fe2O3, the middle absorption type Fe3O4 film is the main factor affecting the reflectivity. The interference effect caused by the outermost Fe2O3 film affects the stability of the reflectivity. The innermost FeO film Contributions can be ignored.