Defining a new process window for LPBF of Ti-6Al-4V based on micro-warping phenomena

Despite the many advantages that additive technologies have over subtractive ones, low porosity levels, good mechanical properties, and low residual stresses remain the most pressing issues that need further research. In particular, the latter can cause a mismatch between the desired geometry and the geometry that can be achieved. In this work, a process window for the Laser Powder Bed Fusion (LPBF) process of Ti-6Al-4V alloys, has been identified. The micro-warping phenomenon, which causes the deformation of the printed part during the printing job and the failure of the process, was taken into account together with the parts' strength, ductility, and porosity. The occurrence of micro-warping phenomena was assessed by the new Warping Alert (WA) parameter, which depends on the parameters P and v. It was found that, before balling, micro-warping limits the process window in the laser power (P) – laser velocity (v) plane. However, optimal mechanical performances can be found in the proximity of the micro-warping zone, thus making it extremely important to determine the WA threshold value to the process design.