Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam

Abstract

Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility.

Laser Powder Bed Fusion of Metal Coated Copper Powders

“…This is supported by the decreased crack density in the lower part of the sample fabricated from Coated Ni2.4, which is presumably due to the higher temperature close to the preheated stainless steel base plate resulting in lower residual stresses. Possible techniques to reduce cracking include preheating [38], wobbling of the laser scan head [39] and other methods of controlling the residual stress. A systematic study of these approaches was not in the scope of this publication and will be part of future work.…”

A review: Suppression of the solidification cracks in the laser welding process by controlling the grain structure and chemical compositions

“…However, the suppression of cracks by an infinite-shape pattern at 100 HZ and 3.5 m/min is feasible. The equiaxed grains at the center of the welding by this oscillation fluctuate and have different proportions (Kang et al, 2018).…”

Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction

“…Several technological and metallurgical approaches have been proposed to prevent solidification cracks in laser welding of 6xxx aluminium alloys. These include: (i) modification of chemical composition through the use of filler wires [25,26]; (ii) refinement of grain structure by means of magnetic stirring, laser beam oscillation and addition of alloying elements [19,24]; and, (iii) temporal modulation of thermal history provided by beam shaping and beam oscillation [27].…”