Determination of plasma temperature and electron density of AZ31 magnesium alloy utilizing laser-induced breakdown spectroscopy

In this study, optical emission spectra (OES) of AZ31 Magnesium alloys plasma have been analyzed using laser-induced breakdown spectroscopy (LIBS) system. For this purpose, the measurements have been performed using nanosecond Q-switch Nd: YAG laser with wavelengths (355, 532 and 1064 nm) and various laser energies ranging from 50 to 200 mJ in air at atmospheric pressure. Electron number density (Ne) was measured based on the Stark broadened line profile of Mg I corresponding to a wavelength 285.21 nm and to a transition (3s3p, 1p0 → 2p63s2, 1s0). Boltzmann plot method was used to measure electron temperature (Te) via resolved magnesium neutral spectral lines of 277.66 nm, 333.21 nm, 382, 93nm and 383.23 nm. A regular increase in the spectral line intensities and the plasma parameters, Te from 9567 to 23683 K and Ne from 1.22*1018 to 3.9*1018 cm−3, was observed with the increase of laser energy. In addition, the validity of the postulation of local thermodynamic equilibrium (LTE) was discussed giving consideration of the results obtained. It is worth mentioning that the intensity of the emission lines is remarkably higher for UV at 355 nm compared to IR at 1064 nm of laser wavelengths, which can be explained in terms of enhancing the mass-ablated at shorter wavelength.