Laser welding of aluminium alloy 5083

Abstract

There are two laser welding mechanisms, keyhole mode and conduction mode. Keyhole welding is widely used because it produces welds with high aspect ratios and narrow heat affected zones. However keyhole welding can be unstable, as the keyhole oscillates and closes intermittently. This intermittent closure causes porosity due to gas entrapment. Conduction welding, on the other hand, is more stable since vaporisation is minimal and hence there is no further absorption below the surface of the material. Conduction welds are usually produced using low-power focused laser beams. This results in shallow welds with a low aspect ratio. In this work, high-power CO 2 and YAG lasers have been used to produce laser conduction welds on 2mm and 3mm gauge AA5083 respectively by means of defocused beams. Full penetration butt-welds of 2mm and 3mm gauge AA5083 using this process have been produced. It has been observed that in this regime the penetration depth increases initially up to a maximum and then decreases with increasing spot size (corresponding to increase in distance of focus above the workpiece). Results of comparison of tensile strength tests for keyhole and conduction welds are shown. This process offers an alternative method of welding aluminium alloys, which have a high thermal conductivity.

Conduction laser welding

“…The problems in using keyhole mode in laser welding of aluminium alloys can be overcome by using conduction laser welding. Some examples of the application of conduction laser welding © Woodhead Publishing Limited, 2013 in aluminium are the work done by Morgan and Williams, 9 by Okon et al 37 and by Sanchez-Amaya et al 16,55 The results showed that by using conduction mode laser welding, it is possible to obtain welds free of pores and of cracks, two defects normally associated with laser welding of aluminium. In terms of the penetration achieved, Okon et al were able to obtain full penetration in 3 mm thick AA5083, 37 Sanchez-Amaya et al were also able to obtain full penetration on 3 mm thick AA5083 and 2.3 mm penetration on AA6082 (Fig.…”

“…14 Conduction welding can be a viable alternative to keyhole welding mainly because it is a very stable process and easier to obtain high quality welds free of pores and spatter. 37 This mode takes place when the vaporisation of the material is insignificant, in other words, when the thermal power density is not high enough to cause boiling. 38 Another advantage of conduction laser welding is that it can be made with a significantly low laser cost, because it does not require a high beam quality or very high power.…”

Laser Beam Welding of Titanium Additive Manufactured Parts

“…As keyhole welding occurs at high laser intensities, causing the material to evaporate locally [6], it forms a capillary filled with hot metal gas or plasma that can extend over the complete depth of the workpiece. This property allows high welding speeds with a small Heat Affected Zone (HAZ) and better mechanical properties.…”

An automated inverse method to calibrate thermal finite element models for numerical welding applications

“…For the current study, the procedure was implemented for LBW. As the energy density available was higher than conventional arc welding (10 10 W/m 2 compared to 10 8 W/m 2 [31]), the laser beam can operate in both the conductive and keyhole regime [31];therefore, the geometry of the melt pool can range from a shallow elliptical shape with a low penetration depth in the conductive regime [32] to a narrow, parallel sided geometry, with a deep penetration depth in the keyhole regime [33]- [35]. This is often referred to as the nail head geometry.…”