Effect of ultra-high-speed laser melting deposition process on performance of Al-Mg-Sc high-strength aluminum alloy

In order to clarify the microstructure of Al-Mg-Sc high-strength aluminum alloy prepared by ultra-high speed laser melting deposition，and study the relationship between structure and properties，Al-Mg-Sc high-strength aluminum alloy was prepared by using 7075 aluminum alloy as matrix and self-developed equipment（LDF3000-40 laser melting deposition machine）. The effect of laser scanning rate on the microstructure and tensile properties of the materials was investigated. The results show that there are no obvious defects such as pores and cracks in the samples deposited by ultra-high speed laser melting，but contain a few small keyholes. The samples are composed of fine α-Al equiaxial crystals and dispersed Al3（Sc，Zr）particles. The effect of scanning rate on mechanical properties is further studied by numerical simulation. It is found that the faster scanning rate of laser in the range of 0.1-1 m/s can reduce the accumulation of powder materials and porosity of the surface of the deposition layer，thus the mechanical properties can be improved. The maximum tensile strength is 303 MPa and elongation at break is 22.5%.