Surface mechanical properties of 2024-T351 aluminum alloy strengthened by cryogenic laser peening

In order to investigate the effects of cryogenic laser peening(CLP) on the surface mechanical properties of 2024-T351 aluminum alloy, the Nd:YAG nanosecond pulsed laser was used to carry out the laser peening on 2024-T351 aluminum alloy at room temperature(25℃) and cryogenic temperature(-100℃), respectively. The micro-hardness, residual stress and microstructure of the samples were tested and analyzed, and the strengthening mechanism of CLP was discussed by the laser induced microstructure at room temperature and cryogenic temperature. The results show that, the dislocation density of CLP-treated samples is higher and the grain size on the surface is smaller than that of LPed after dynamic recrystallization due to the effect of cryogenic temperature on the sliding and annihilation of the dislocation. The surface micro-hardness and residual compressive stress of CLP-treated samples are respectively increased by about 20.3% and 21.6%, compared with LP samples, and the surface mechanical properties of 2024-T351 aluminum alloy are improved.