Metallurgical Abstracts on Light Metals and Alloys vol.54
Lattice distortion in selective laser melting (SLM)-manufactured unstable β-type Ti-15Mo-5Zr-3Al alloy analyzed by high-precision X-ray diffractometry
Aya Takase*, Takuya Ishimoto*, Ryoya Suganuma* and Takayoshi Nakano*
*Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University
[Published in Scripta Materialia, Vol. 201 (2021), 113953]
https://doi.org/10.1016/j.scriptamat.2021.113953
E-mail: ishimoto[at]mat.eng.osaka-u.ac.jp
Key Words：Selective laser melting, β-type titanium alloys, Crystal structure, Residual stressesX-ray diffraction
A peculiar lattice distortion in a selective laser melting (SLM)-manufactured unstable β-type Ti-15Mo-5Zr-3Al was observed for the first time, through high-precision X-ray diffraction (XRD) analyses. After SLM, Ti-15Mo-5Zr-3Al exhibited a body-centered-tetragonal structure instead of a body-centered-cubic structure; the c-axis was 0.63% shorter than the a-axis. The XRD analyses also revealed tensile residual stresses of 210 ± 12 MPa at the specimen surface. A numerical simulation indicated rapid cooling during the SLM, which could have caused the residual stresses. A comparison of the partially stress-released SLM specimen and an electron beam melting-manufactured specimen with negligible residual stress suggested that the residual stress caused by the rapid cooling in SLM induced the lattice distortion. This finding is not consistent with the previous understanding that residual stress changes the lattice parameter without lattice distortion. This study provides new insight into lattice distortion generated by a combination of SLM-specific ultrarapid cooling and unstable phases.
