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In the present study, laser periodic structuring of titanium-based alloy (Ti-6Al-4V) has been carried out using Ti:Sapphire laser with the wavelength of 800 nm and pulse duration of 3 ps and 100 fs with varying peak fluence and scan speed. After laser irradiation, the topography of the surface has been recorded using 3D surface profilometer. Laser surface processing leads to the formation of a periodically patterned surface with the average ablation depth of 37.25 µm-42.13 and average surface roughness of 0.991-1.862 µm as compared to 0.169 µm average roughness of as-received Ti-6Al-4V. In the microstructure, there is presence of fine periodic ripples with an average ripple width of 0.48 µm to 0.54 µm when processed with 3 ps laser and the average ripple width of 0.17 μm in addition to the presence of very fine pits, deposited particle, and oxide dispersed surface when processed with 100 fs laser. The microhardness of the surface is improved (395 VHN-373 VHN ) as compared to 282 VHN of as-received Ti-6Al-4V. There is a significant improvement in the corrosion resistance in terms of a decrease in corrosion rate (0.0037 to 0.0008 mm/year) in laser surface processed sample as compared to as-received Ti-6Al-4V (0.0932 mm/year) in Hank’s solution and also increase in pitting corrosion resistance in terms of increase in critical potential for pit formation (Epit) under a few employed parameters with both 3 ps laser (at a laser fluence of 0.063 J/cm2 and a scan speed of 20 mm/sec) and 100 fs laser (at a laser fluence of 0.63 J/cm2 and at a scan speed of 60 mm/sec).

In the present study, a galvanized steel and a AA6082 aluminum alloy sheet of 2 mm thick were weld-brazed by applying laser and using 2-mm-diameter solid Al-12% Si filler wire at 2.5 m/min wire feed rate and 2 m/min laser scan speed at varying laser power (4.0, 3.5, 3.0 kW) in flange configuration. The microstructural investigation of the laser weld-brazed joints revealed the presence of two-layered intermetallic compound at steel/braze seam interface. The corresponding x-ray diffraction analysis of the steel/braze seam interface showed the presence of Al-Fe-Si-based ternary intermetallic phases. SEM and EDS analysis of the braze seam revealed the presence of α-Al grains surrounded by Mg2Si phase in the grain boundary region. Fine intermetallic layer was observed at lower heat-input condition. The corrosion performance of the brazed joints was studied with the help of immersion, salt spray, and electrochemical polarization tests in different electrolytes containing NaCl salt. Brazed joints experienced galvanic corrosion during immersed in corrosive media. From the salt spray test, it was revealed that galvanized steel was highly susceptible to corrosion compared to Al-rich phase. The polarization results showed a substantial change in corrosion resistance from steel interface to the brazed region due to the variation in microstructure. The samples brazed with low heat-input showed better corrosion resistance as compared to the joints made with high heat-input. Post-corrosion microstructure revealed intergranular corrosion at the brazed joint along with pit formation.

Partial replacement of steel by Aluminium (Al) alloys is a promising approach adopted by automotive sector to improve fuel efficiency without compromising on the strength. However, this results in the generation of dissimilar welds of Al alloys and steel. Understanding the corrosion behavior of Al alloys–steel welds as a function of welding parameters is critical in the successful application of such alloys. The present study reports the intergranular corrosion behavior of T6 heat-treated AA6061 Al alloy-galvanized mild steel lap joints, welded by metal inert gas welding–brazing technique as a function of different welding parameters, viz. weld speed (4-6 m/min) and wire feed rate (0.8-0.9 m/min), following ASTM G 67-04. Weld characterization was performed by field emission scanning electron microscopy (FESEM), x-ray diffraction and nano-hardness measurement. Results indicate heavy dissolution and metal loss at the interface. A high volume fraction of Al-Fe intermetallics was precipitated at the weld interfaces, resulting in high hardness and higher localized corrosion. The thickness of Al-Fe intermetallic layer increased with increasing wire feed rate and lower weld speed which enhanced the severity of galvanic and intergranular corrosion.

In the present study, laser-brazed AA6082 to DX56-galvanized steel joints were investigated to understand the influence of process parameters on joint strength in terms of intermetallic layer formation. 1.5-mm-thick sheet of aluminum alloy (AA6082-T6) and galvanized steel (DX56) sheet of 0.7 mm thickness were laser-brazed with 1.5-mm-diameter Al-12% Si solid filler wire. During laser brazing, laser power (4.6 kW) and wire feed rate (3.4 m/min) were kept constant with a varying laser scan speed of 3.5, 3, 2.5, 2, 1.5, and 1 m/min. Microstructure of brazed joint reveals epitaxial growth at the aluminum side and intermetallic layer formation at steel interface. Intermetallic layer formation was confirmed by EDS analysis and XRD study. Hardness profile showed hardness drop in filler region, and failure during tensile testing was initiated through the filler region near the steel interface. As per both experimental study and numerical analysis, it was observed that intermetallic layer thickness decreases with increasing brazing speed. Zn vaporization from galvanized steel interface also affected the joint strength. It was found that high laser scan speed or faster cooling rate can be chosen for suppressing intermetallic layer formation or at least decreasing the layer thickness which results in improved mechanical properties.