Spectroscopic Analysis of Plasma Induced in Laser Welding of Aluminum Alloys

Abstract

This paper describes the features and characteristics of plasma induced in the pulsed YAG laser welding of Al-Mg alloys in air and argon atmospheres. In the air environment, the identified spectra are atomic lines of Al, Mg, Cr, Mn, Fe and Zn, and singly ionized Mg line, as well as strong molecular spectrum of AlO, MgO and AlH. It has been confirmed that the resonant lines of Al and Mg were strongly self-absorbed. These facts have shown that the laser-induced plasma is relatively a low temperature and high density metallic vapor. The intensities of molecular spectra of AlO and MgO are different each other depending on the power density of laser beam. Under the low power density irradiation condition, the MgO band spectrum is predominant in intensity, while the AlO spectrum became much stronger with the increase in high power density. This was attributed by the great difference in boiling point and vaporization energy of Al and Mg. In argon atmosphere the band spectra of MgO and AlO completely vanished, but AlH molecular spectra is detected clearly. The hydrogen source is presumably the hydrogen solved in the base metal, absorbed water on the surface oxide layer, or H2 and H2O in the shielding gas.

Low Speed Laser Welding of Aluminium Alloys Using Single-Mode Fiber Lasers

“…10 13 cm -3 . Kim et al (2004) did a similar study and found similar results for even higher irradiations (~ 32 MW/ cm 2 ), namely the vapor/plasma temperature was very close to the boiling point of aluminium. Fig.…”

Inherent instability investigation for low speed laser welding of aluminum using a single-mode fiber laser

“…To confirm the above finding, we reviewed available literature on the vapor/plasma temperature for Nd:YAG (similar wavelength as fiber laser) laser welding of aluminum alloys. Kim and Matsunawa (1996) used a pulse shapeable YAG laser with irradiations of up to 1 MW/cm 2 on 5000 series aluminum alloys and determined that the vapor/plasma plume was very weakly ionized, with approximate temperatures around 3280 K (barely above the vaporization temperature of aluminum) and electron densities of approximately 1.85 × 10 13 cm −3 . Kim et al (2004) did a similar study and found similar results for even higher irradiations (∼32 MW/cm 2 ), namely the vapor/plasma temperature was very close to the boiling point of aluminum.…”

Vapor plume and melted zone behavior during dissimilar laser welding of titanium to aluminum alloy

“…This difference in luminosity can be explained by a lower plume temperature of Al compared to Ti, determined by a lower absorptivity of the laser radiation (Table 1) and higher energy necessary to excite Al atoms, according to NIST database. 15 Kim and Matsunawa 17 reported the plume temperature barely above the boiling point for 5000 series aluminum alloys welded with Nd:YAG laser having an energy density of 1 MW/cm 2 . Kim et al 18 obtained the same result for an even higher energy density of 32 MW/cm 2 .…”

“…15 Kim and Matsunawa 17 reported the plume temperature barely above the boiling point for 5000 series aluminum alloys welded with Nd:YAG laser having an energy density of 1 MW/cm 2 . Kim et al 18 obtained the same result for an even higher energy density of 32 MW/cm 2 . In the present experiments, the energy density was 9.5 MW/cm 2 , and taking into account close wavelengths of Yb:YAG and Nd:YAG laser, it can be supposed that the plume temperature should also near the boiling point of aluminum.…”