This Master’s Thesis, entitled Laser Surface Remelting of Magnesium Alloy AZ80, presents basic information about the effect of laser surface remelting using Nd:YAG laser on: surface roughness, microstructure, microhardness, corrosion rate, and residual stresses of magnesium alloy AZ80 with approximately 8 mas. % Al and 0.7 mas. % Zn. Due to low absorption of magnesium of laser light, graphite absorber was used. One of the goals of the thesis was finding optimal laser process parameters for maximum process efficiency (i.e. biggest laser beam diameter and laser scanning speed) and 50 % laser path overlapping while using laser power with minimum negative influence on surface roughness. Based on measurements, optimal laser process parameters were selected, i.e. P = 40 W, dB ≈ 1.9 mm, t = 10 ms, v = 0.5 mm/s, and ν = 1 Hz. Surface roughness of laser remelted surface was Sa = 20.15 um. After fine grinding Sa = 5.31 um was achieved. Depth of laser remelted zone was 330 um. Microhardness of laser remelted zone was approximately 140 HV0.05, which is almost 40 % improvement compared to core. Tensile residual stresses of 100MPa to 150MPa were introduced by laser surface remelting. Corrosion rate of laser remelted surface was approximately 3 times slower compared to non–remelted surface, using Tafel extrapolation method.
|
