Analyzing the Mechanical Behavior of Additive Manufactured Ti-6Al-4V Using Digital Image Correlation

Abstract

Demands from the market to produce high performance products with low lead times and more customized production are continuously increasing. This has resulted in a growing market for additively manufactured components. Two printing techniques, selective laser melting (SLM) and electron beam melting (EBM), were compared by investigating their resulting mechanical performance. Samples manufactured from Ti-6Al-4V powder were provided from Arcam AB and Lasertech LSH AB. Both companies made two different build layer orientations, one set was built parallel to the tensile direction (X) and another perpendicular to the tensile direction (Z). Half of the samples produced with SLM were heat treated. Samples were tested under quasi-static tensile loading in combination with Digital Image Correlation (DIC) to determine the localized strains. From each tensile test, Young’s modulus, yield strength (Rp0.2), ultimate tensile strength (UTS) and elongation at break were obtained. A Vickers hardness test (HV2) was performed on polished surfaces. Optical microscope was used in order to analyze the microstructure of the samples. For all samples it was seen that the grains have grown in an epitaxial manner in the same direction as the building direction. An explanation for this was the re-melting of layers. Results from the DIC analysis indicate that the X-built EBM and SLM samples contain localized strains elongated perpendicular to the tensile direction and potentially connect to the areas of the prior β-grains. The Z-built EBM and SLM samples seem to have localized strains elongated in the tensile direction. By comparing the strain fields of the SLM samples it can generally be noted that the strain fields are more homogeneous in the Z-built samples. From the mechanical tests it was shown that different mechanical properties are obtained in samples from the different manufacturing processes.