Towards enhanced mechanical performance of Al/steel welded-brazed joints via laser surface texturing modification

Abstract

Laser texturing is a promising technology with wide-ranging applications in surface processing. In this study, a nanosecond laser was used to ablate the surface of Q355 steel, creating grooves of varying depths by different processing times. Satisfactory Al/Steel joints were obtained under different groove depths (0 μm, 6 μm, 26 μm and 56 μm). Interfacial microstructure evolutions were investigated and the observed results indicated that introduction of texture would enhance interfacial specific surface area, promote degree of atomic diffusion, thicken interfacial IMCs (intermetallic metallic compounds) while maintain interfacial reaction (η-Fe2(Al,Si)5 + θ-Fe(Al,Si)3). Numerical simulations results illustrated that existence of texture would reduce interfacial peak residual stress, homogenize residual stress distribution and induce compressive stress in the groove. Highest strength of 111 MPa with the fracture mode of tough-brittle compound fracture was produced in the joint when laser texturing processing times were 20, which was nearly 40 % higher compared to the untreated joint (80 MPa). This study provides a novel method to improve joints mechanical properties for laser welding-brazing of Al/Steel system, which may also provide a theoretical reference for the application of other dissimilar metal systems.

Keywords

• Laser welding-brazing al/steel
• Laser texturing
• Interfacial microstructure
• Residual stress
• Joint strength