The Effect of Building Direction on Microstructure and Microhardness during Selective Laser Melting of Ti6Al4V Titanium Alloy

During the last few years, additive manufacturing has been more and more extensively used in several industries, especially in the aerospace and medical device fields, to produce Ti6Al4V titanium alloy parts. During the Selective Laser Melting (SLM) process, the heterogeneity of finished product is strictly connected to the scan strategies and the building direction. An optimal managing of the latter parameters allows to better control and defines the final mechanical and metallurgical properties of parts. Acting on the building direction it is also possible to optimize the critical support structure. In particular, more support structures are needed for the sample at 0 degrees, while very low support are required for the sample at 90 degrees. To study the effects of build direction on microstructure heterogeneity evolution and mechanical performances of selective laser melted Ti6Al4V parts, two build direction samples (0 degrees, 90 degrees) were manufactured and analyzed using optical metallographic microscope (OM) and scanning electron microscopy (SEM). Isometric microstructure reconstruction and microhardness tests were carried out in order to analyze the specimens. The obtained results indicate that the build direction has to be considered a key geometrical parameter affecting the overall quality of the obtained products.