Quantitative CF-LIBS analysis of alloys via comprehensive calibration of plasma temperature and spectral intensity

Abstract

The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of each element in alloys plays a key role in metallurgy quality control and material classification processes. A quantitative calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method, which carries out comprehensive calibration of plasma temperature and spectral intensity by using a second-order iterative algorithm and a similar matrix standard sample, is proposed to compare the standard errors that correspond to various plasma temperatures and calibration coefficients. Once the minimal standard error is found, we can optimize both the plasma temperature and the calibration coefficient of the minor element emission line, and establish the quantitative analysis model to realize accurate elemental composition measurements. In our experiments, the ZBY910 copper-lead alloy is selected to be the standard sample. Here, 6 Cu I lines and 5 Pb I lines are utilized to draw the Boltzmann plots, and the plasma temperature is predicted to be in the range of 5000–10000 K. Experimental results show that, the optimal plasma temperature and correction coefficient are found to be 7710 K and 0.61, respectively, as the standard error reaches its minimum of 0.06. Compared to conventional CF-LIBS analysis, the relative errors for major elements Cu and Zn and minor element Pb in the samples have been reduced from 13%, 20%, and 74% to 4.4%, 6.2%, and 17.7%, respectively, which are much superior to those of the conventional CF-LIBS method. This new method has greatly improved the quantitative analysis accuracy of CF-LIBS and realized more accurate measurement of both major and minor elements in alloy samples. It is expected to promote the application of CF-LIBS technology in fields such as metallurgical quality monitoring, material identification, classification, etc.