Abstract
Laser peening without coating (LPwC) using a palmtop-sized microchip laser has improved the residual stresses (RSs) and fatigue properties of A7075 aluminum alloy. Laser pulses with a wavelength of 1.06 μm and duration of 1.3 ns from a Q-switched Nd:YAG microchip laser were focused onto A7075 aluminum alloy samples covered with water. X-ray diffraction revealed compressive RSs on the surface after irradiation using laser pulses with an energy of 1.7 mJ, spot diameter of 0.3 mm, and density of 100–1600 pulse/mm2. The effects were evident to depths of a few hundred micrometers and the maximum compressive RS was close to the yield strength. Rotation-bending fatigue experiments revealed that LPwC with a pulse energy of 1.7 mJ significantly prolonged the fatigue life and increased the fatigue strength by about 100 MPa with 107 fatigue cycles. The microchip laser used in this study is small enough to fit in the hand or be mounted on a robot arm. The results may lead to the development of tools that extend the service life of various metal parts and structures, especially outdoors where conventional lasers are difficult to apply.
Highlights
The standard deviation of the residual stresses (RSs) was about ±10 MPa
The RSs afforded by both Laser peening without coating (LPwC) modes did not differ
X-ray diffraction (XRD) revealed that significant compressive RSs were generated on A7075-T73, and the affected depth was about
Summary
In the early stage of LSP development, high-power lasers such as 100 J-class Nd:glass lasers were used [1]; recently, 10 J-class Nd:YAG or Nd:YLF lasers have been commercially employed [10,11]. When using such high-power lasers, a surface coating (an adherent metal tape, polymer tape, or paint) is necessary to prevent surface melting and damage [12,13]
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