Processing of a metastable titanium alloy (Ti-5553) by selective laser melting

Abstract

The metastable beta titanium alloy Ti-5Al-5V-5Mo-3Cr is characterised by multifaceted mechanical properties (high - strength, hardened, ductile) depending on applied heat treatment. Compared to α-β titanium alloy Ti-6Al-4V, a higher tensile strength up to 1400 MPa as well as a yield strength of 1250 MPa can be achieved. As a result, Ti-5553 is used for special aerospace applications e.g. landing gear components or helicopter rotors. Aim of this paper is to study the processibility of Ti-5553 by using selective laser melting. First, a suitable and stable process parameter set for a reference grain fraction (10–63 μm) have been developed. Second, variations of grain size distribution will be taken into account, so that a high material density as well as high surface quality can be achieved. Furthermore, an identical process window was applied on fine and coarse grain fractions to show effects regarding material porosity. Material densities above 99.93% were achieved by optimisation of energy input during selective laser melting process. However, the use of reference fraction (10–63 μm) allowed the highest material density. Regarding to surface quality, an impact of coarse grain (53–63 μm) was identified and an optimised grain size distribution derived. An optimum averaged surface roughness could be calculated, using a grain size between 25–32 μm.

Keywords

• Additive manufacturing
• Selective laser melting
• Ti-5553
• Process parameter
• Grain fraction