Improving Fatigue Performance of Laser-Welded 2024-T3 Aluminum Alloy Using Dry Laser Peening

• Main Authors: Tomokazu Sano, Takayuki Eimura, Akio Hirose, Yosuke Kawahito, Seiji Katayama, Kazuto Arakawa, Kiyotaka Masaki, Ayumi Shiro, Takahisa Shobu, Yuji Sano
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Metals
• Subjects: dry laser peening; femtosecond laser; shock wave; laser welding; 2024 aluminum alloy
• Online Access: https://www.mdpi.com/2075-4701/9/11/1192

The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance of laser-welded 2024 aluminum alloy containing welding defects such as undercuts and blowholes. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. As a result, DryLP treatment improved the fatigue performances of welded specimens with and without the weld reinforcement almost equally. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes, as stress concentration at the defects did not significantly influence the fatigue performance.