Laser line patterning for improving bond joining strength of Al-Mg alloy

Abstract

Aluminium-Magnesium alloy has an excellent corrosion resistant property and is used in several aeronautical and maritime applications. Adhesive bonded joints made with adhesives have been evolved as a reliable and environment friendly solution for joining different materials including metals, composites and polymers. There has been tremendous improvement in the quality and bond strength of adhesive based joints due to improvement in adhesive properties. Adhesive joining are specially useful in intricate places were traditional joining methods can’t be applied. Surface preparation prior to adhesive application is an important step to have a reliable joint strength. In this research work, nanosecond fiber laser was utilized for pre-treatment of surfaces which will then be adhesively bonded. Simple line patterning type of design was created on Al-Mg alloy (AA5754) surfaces. Texturing was done in three types of processing environment which is open air processing, underwater processing, and under flowing water conditions. Experiments were designed to evaluate the impact of working environment on adhesive joint strength. Also, the effect of texture density and depth were investigated by changing scanning speed and line distances of the fabricated design. Contact angle of surface textures were determined to find surface wettability. Tensile strength of adhesive bonded surfaces were assessed by performing shear strength test. Flowing water condition produced texture depths up to 390 µm and surface roughness up to 84 µm. Surfaces patterned with flowing water environment were observed to have 2.36 times higher adhesive bonding strength compared to untextured plain samples. Similarly, open air texturing resulted in 201.3% and static water texturing in 193.5% higher adhesive strength compared to plain untextured samples.