Determination of Species Concentrations of Ti-6Al-4V Titanium Alloys using Calibration Free Laser Induced Breakdown Spectroscopy

Abstract

In this study, Calibration-free Laser-induced breakdown spectroscopy (CF-LIBS) was applied to quantitatively analyze the elemental composition of Ti-6Al-4V titanium based alloy samples with no need for matrix-matched calibration procedure. Nd:YAG pulsed laser operating at a wavelength of 1064 nm was focused onto the sample to generate plasma. The spectrum of plasma was recorded using spectrophotometer then compared to NIST spectral lines to determine characteristic wavelengths, energy levels and other spectroscopic parameters. The values of plasma temperature obtained using Boltzmann plot for four examined samples ranged from 7439 to 6826 K while the electron density for each element was determined using Boltzmann-Saha equation. The concentration of Ti, Al, V and Fe has been determined and were within the samples nominal concentrations obtained from XRF analysis.  The calculated average relative errors of Ti, Al, V and Fe were 0.39%, 4.38%, 4.94 % and 8.2 %, respectively. Finally, there was a direct proportionality relation between the ratio of ionic to neutral emission lines of Ti for four samples and the surface hardness values measured mechanically using Vickers hardness test. The ratio at   had the best linear regression value (R2=0.95) which indicates the best correlation with surface hardness.