Microstructure and tensile properties of the sub-micro and nano-structured Al produced by laser surface melting

Experiments were conducted to study the microstructure and tensile properties of the sub-micro and nano-structured Al produced by the Nd:YAG pulsed laser surface melting (LSM). The surface and longitudinal section microstructures of the Al samples after LSM were analyzed. The solidification microstructures in the LSM region were very fine which was beneficial to improve the properties of the Al sample. The tensile behavior and the relevant fracture mechanism of the LSM layer on the Al surface were investigated based on the analyses of the tensile test results. The fracture morphologies in the LSM region were small and shallow dimples with the size of 0.4–1 μm. It indicated that the Al sample showed the ductile behavior because the grains were refined effectively after LSM. Furthermore, the typical amorphous fracture morphology with the fish scale structure was also obtained at the strain rate of 1.0 × 10−4 s−1 after LSM with the laser power density of 3.65 × 109 W/m2.