锌铝镁镀层汽车板镀层相的X射线衍射分析

为了对锌铝镁镀层汽车板镀层相进行表征,进而指导生产现场工艺调整及优化,首先采用X射线衍射仪(XRD)对测试参数进行了优化,然后根据最优测试参数,对7种不同镀层质量的锌铝镁镀层汽车板镀层相组成进行了定性定量分析。结果表明,优化后的锌铝镁镀层XRD相分析的最佳测试参数为小角掠射模式,窄狭缝,步长0.02°~0.04°,扫描速度不大于2°/min,扫描角度范围40°~51.5°。对7种不同镀层质量的锌铝镁镀层试样进行分析,发现物相组成相同,均由Zn、MgZn₂和AlMg₄Zn₁₁组成;镀层质量在50g/m²以下时,随着镀层质量的增加,镀层相中MgZn₂和AlMg₄Zn₁₁的质量分数先增大后减小,但差别不大;镀层质量从50g/m²增加到70g/m²时,镀层相中Zn的质量分数降低,MgZn₂和AlMg₄Zn₁₁的质量分数均增加,且MgZn₂的增长速率大于AlMg₄Zn₁₁。常规的XRD只能进行初步的半定量分析,而实验通过优化仪器参数提高了XRD半定量精度,进而取代了传统的化学法进行定量分析,及时了解了镀层物相组成,实验结果将为生产现场进行镀层工艺优化提供理论指导。

X-ray diffraction analysis of coating phase for zinc-aluminum-magnesium coating automobile sheet

In order to characterize the coating phase for zinc-aluminum-magnesium coating automobile sheet, and further guide the process adjustment and optimization in production field, the testing parameters were firstly optimized by X-ray diffractometer (XRD). Then the composition of the coating phase in zinc-aluminum-magnesium coating automobile sheet with seven different coating mass was qualitatively and quantitatively analyzed based on the obtained optimum testing parameters. The results showed that the optimum testing parameters for XRD phase analysis of zinc-aluminum-magnesium coating were as follows: small angle glancing incidence mode, narrow slit, step length of 0.02°-0.04°; the scanning speed was not higher than 2°/min, and the scanning angle was in range of 40°-51.5°. From the analysis of the zinc-aluminum-magnesium coating samples with seven different coating mass, it was found that the phase composition was the same and composed of Zn, MgZn₂ and AlMg₄Zn₁₁. When the coating mass was less than 50g/m², the mass fraction of both MgZn₂ and AlMg₄Zn₁₁ in coating phase increased firstly and then decreased with the increasing coating mass, but the difference was not significant. When the coating mass increased from 50g/m² to 70g/m², the mass fraction of Zn in coating phase decreased, while the mass fraction of both MgZn₂ and AlMg₄Zn₁₁ increased; meanwhile, the increasing rate of MgZn₂ was higher than that of AlMg₄Zn₁₁. Traditional XRD could be only used for the preliminary semiquantitative analysis. The optimization of instrumental parameters in experiments could enhance the semiquantitative precision of XRD, thus it could replace the conventional chemical method for quantitative analysis. The in-time understanding of composition in coating phase could provide the theoretical guidance for the optimization of coating process in production field.