Abstract
By means of additive manufacturing, the production of components with nearly unlimited geometrical design complexity is feasible. Especially, powder bed fusion techniques such as electron beam powder bed fusion (PBF-EB) are currently focused. However, equal material properties are mandatory to be able to transfer this technique to a wide scope of industrial applications. Within the scope of this work, the mechanical properties of the PBF-EB-manufactured Ti6Al4V alloy are investigated as a function of the position on the building platform. It can be stated that as-built surface roughness changes within building platform whereby highest surface roughness detected by computed tomography (Ra = 46.0 ± 5.3 µm) was found for specimens located in the front of the building platform. In contrast, no significant differences in relative density could be determined and specimens can be assumed as nearly fully dense (> 99.9%). Furthermore, all specimens are affected by an undersized effective diameter compared to the CAD data. Fatigue tests revealed that specimens in the front of the building platform show slightly lower performance at higher stress amplitudes as compared to specimens in the back of the building platform. However, process-induced notch-like defects based on the surface roughness were found to be the preferred location for early crack initiation.
Highlights
As one of the most common used titanium alloys, Ti6Al4V is known for its good strength-to-weight and stiffness-toweight ratio as well as other advantageous characteristics
The average surface roughness value for all investigated specimens which were tested with tactile surface roughness tester was found to be Ra = 20.9 ± 1.3 μm whereby Fig. 2a shows the arrangement of all specimens on the building platform (BP) with their associated Ra value
To transfer the Powder bed fusion (PBF)-EB process towards industrial applications, the process–structure–property relationships have to be understood in detail
Summary
As one of the most common used titanium alloys, Ti6Al4V is known for its good strength-to-weight and stiffness-toweight ratio as well as other advantageous characteristics. Powder bed fusion (PBF) is an AM technique (cf ASTM F42 Committee [4]) based on a 3D-CAD model. Powder layers are deposited on a building plate and a high-energy source (laser or electron beam) fuses the powder bed by creating small melt pools. Laser powder bed fusion (PBFLB/M) manufactures parts in a chamber filled with inert gas [2]. Electron beam powder bed fusion (PBF-EB) applies a high vacuum in the process chamber at increased processing temperatures (> 700 °C) [6, 7]. According to the possible process parameters, the PBF-EB process is advantageous as it can result in reduced residual stresses [8] and minor contamination of other elements such as oxygen [2]
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