Limitations of linear energy density for laser powder bed fusion of Mg-15Gd-1Zn-0.4Zr alloy

Abstract

Linear energy density is often used as a design parameter to select laser power and scanning speed for the laser powder bed fusion (LPBF) of alloys. In the present study, the effects of laser power and scanning speed on the depth and width of remelted track and porosity of the as-built Mg-15Gd-1Zn-0.4Zr (GZ151K, wt%) alloy were systematically studied. The experimental results present that the depth and width of remelted track and porosity vary significantly despite using the same linear energy density value but different combinations of laser power and scanning speed values, indicating the limitations of linear energy density when changing laser power and scanning speed simultaneously. Furthermore, sensitivity level analysis was conducted to assess the relative importance of laser power and scanning speed to the depth and width of remelted track and porosity. It was found that scanning speed is more important to the depth and width of remelted track than laser power, while laser power is more important to the porosity than scanning speed. Therefore, using the linear energy density as a design parameter for LPBF is not always reliable, and the present study can provide some guidance for selecting process parameters for the LPBF of alloys. • The depth and width of remelted track and porosity vary significantly despite using the same linear energy density. • Linear energy density is not always reliable especially when changing laser power and scanning speed simultaneously. • Scanning speed is more important to the depth and width of remelted track than laser power. • Laser power is more important to the porosity than scanning speed.