Influence of defects on mechanical properties of Ti–6Al–4V components produced by selective laser melting and electron beam melting

• Published in: Materials & design 2015-12, Vol.86, p.545-554
• Main Authors: Gong, Haijun, Rafi, Khalid, Gu, Hengfeng, Janaki Ram, G.D., Starr, Thomas, Stucker, Brent
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Defects; Electron beam melting; Energy density; Laser beam melting; Mechanical properties; Optimization; Porosity; Selective laser melting; Titanium base alloys; Ti–6Al–4 V
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2015.07.147

This study evaluates the mechanical properties of Ti–6Al–4V samples produced by selective laser melting (SLM) and electron beam melting (EBM). Different combinations of process parameters with varying energy density levels were utilized to produce samples, which were analyzed for defects and subjected to hardness, tensile, and fatigue tests. In SLM samples, small pores in amounts up to 1vol.% resulting from an increase in energy density beyond the optimum level were found to have no major detrimental effect on the mechanical properties. However, further increase in the energy density increased the amount of porosity to 5vol.%, leading to considerable drop in tensile properties. Samples produced using lower-than-optimum energy density exhibited unmelted powder defects, which, even at 1vol.% level, strongly affected both tensile and fatigue properties. In EBM, insufficient energy input was found to result in large, macroscopic voids, causing serious degradation in all mechanical properties. These findings are helpful in process optimization and standardization of SLM and EBM processes. [Display omitted] •Quality of SLM or EBM parts can't be assessed by density measurements alone.•Any unmelted powder inside defects contributes to density but not to strength.•Small pores (up to 1vol.%) caused by excessive energy input are harmless.•SLM process is more tolerant to a little excess energy than insufficient energy.•In EBM, insufficient energy input results in large defects and poor properties.