Influence of the Scanning Strategy on the Microstructure and Mechanical Properties in Selective Electron Beam Melting of Ti-6Al-4V

• Published in: Advanced engineering materials 2015-11, Vol.17 (11), p.1573-1578
• Main Authors: Scharowsky, Thorsten, Juechter, Vera, Singer, Robert F., Körner, Carolin
• Format: Article
• Language: English
• Subjects: Adjustment; Construction; Density; Electron beam melting; Mechanical properties; Microstructure; Scanning; Titanium base alloys
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201400542

Selective electron beam melting (SEBM) is perhaps the fastest production process for additive manufacturing techniques from powder beds. In the present investigation, scan speeds of 10 m s−1 have been used successfully for the melting. Nevertheless, the beam power has to be adjusted to guarantee a density of more than 99.5% for the build samples. The aim of this paper is to investigate the effect of the scan speed and beam power on the microstructure and the mechanical properties of Ti‐6Al‐4V. Therefore, a process map with a window for samples with a density higher than 99.5% and a good geometrical accuracy was developed. But, there are strong differences in microstructure and the resulting mechanical properties. These differences result from changes in the total energy input. In the presented work, strength is found to increase somewhat with decreasing volume energy (60–30 J mm−3) at a scan speed of 4 m s−1 as the cooling rate increases. This causes a change in microstructure, as the α platelet size varies in the range between 400 nm and 1.3 μm. Thus, an increase in ultimate tensile strength of 5% could be realized by adjusted energy input. A parameter field for the scan speed and beam power was observed regarding the influence of the scanning parameters on the microstructure. It can be shown, that the α platelet thickness can be directly influenced. The results correspond very well to the Hall–Petch relation.