β-titanium (Ti) alloys combined with high strength and good ductility have attracted extensive research interest for use in many advanced industrial applications. In this study, laser powder bed fusion (LPBF) parameters were firstly optimised to fabricate highly dense metastable β Ti–12wt% Mo alloy with largely homogeneous structure from low-cost elemental powders. When the laser area energy density (AED) increased to 4 J/mm2 using the simple scan mode, the refractory Mo powder melted and dissolved into the Ti matrix due to the increased melting pool temperature and increased cycles of remelting. However, when the same high AED was used in the chess scanning mode, keyhole-induced defects emerged along the island boundaries. The laser beam delay (LBD) and island spacing (IS) settings were then optimised to eliminate keyhole defects. Additionally, it is found that using low and high AED (e.g. 1.6 and 4 J/mm2 respectively), the builds show significantly different microstructure and mechanical properties. In view of this, a Ti–Mo functional gradient composite (FGC) was fabricated via alternating AEDs of 1.6 and 4 J/mm2 layer-wise. A gradient distribution of α” phase with varied size and quantities across the designed layer boundaries was produced. The Ti–Mo FGC possessed a high compressive yield strength of 1173 (±15) MPa and improved strain hardening capacity. The developed approach demonstrated the potential for the fabrication of FGCs using an in situ alloying based LPBF.
Bibliographical noteFunding Information:
This work was financially supported by the Fundamental Research Program of Shenzhen (Grant No. JCYJ20170412153039309 ), and Guangdong Innovative & Entrepreneurial Research Team Program (No. 2016ZT06C279 ), China. This work was also supported by the Pico Center at SUSTech that receives support from Presidential fund and Development and Reform Commission of Shenzhen Municipality, China . B.C. acknowledges the funding support from the Royal Society, UK (No. RGS\R2\202122 and IEC\NSFC\191319 ).
© 2021 Elsevier Ltd
- Functional gradient composite
- In situ alloying
- Laser powder bed fusion
- Layered structures
- β-Titanium alloys
ASJC Scopus subject areas
- Ceramics and Composites
- Mechanics of Materials
- Mechanical Engineering
- Industrial and Manufacturing Engineering