A yttrium-containing high-temperature titanium alloy additively manufactured by selective electron beam melting

LU Sheng-lu(逯圣路)^{1, 2, 3}, TANG Hui-ping(汤慧萍)², M. Qian(马前)^{2, 4}, HONG Quan(洪权)², ZENG Li-ying(曾立英)², D. H. StJohn³

(1. School of Materials and Metallurgy, Northeastern University, Shenyang 110819, China;
2. State Key Laboratory of Porous Metal Materials (Northwest Institute for Nonferrous Metal Research),
Xi’an 710016, China;
3. Centre for Advanced Materials Processing and Manufacturing,
School of Mechanical and Mining Engineering, The University of Queensland, Qld 4072, Australia;
4. Centre for Additive Manufacturing, School of Aerospace, Mechanical and Manufacturing Engineering,
RMIT University, Melbourne, VIC 3001, Australia)

Abstract:A yttrium-containing high-temperature titanium alloy (Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting (SEBM). The resulting microstructure and textures were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron backscattered diffraction (EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y₂O₃ dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen (7×10^-4, mass fraction) and yttrium (10^-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y₂O₃ precipitates, including cracked or debonded Y₂O₃ particles.

Key words:titanium alloys; additive manufacturing; rare earth elements; yttrium; selective electron beam melting