TY - JOUR
T1 - Effects of post-processing on cyclic fatigue response of a titanium alloy additively manufactured by electron beam melting
AU - Shui, Xiaoli
AU - Yamanaka, Kenta
AU - Mori, Manami
AU - Nagata, Yoshihiko
AU - Kurita, Kenya
AU - Chiba, Akihiko
PY - 2017/1/5
Y1 - 2017/1/5
N2 - To establish the benefits of electron beam melting (EBM) for the fabrication of Ti–6Al–4V alloy components, it is necessary to properly understand the fatigue performance of the alloy. In the present study, we investigated the high-cycle fatigue behaviors of EBM-fabricated Ti–6Al–4V alloy component samples and systematically assessed their correlation with the microstructure, porosity, and (quasistatic) tensile properties of the material. The associated texture evolution and elemental distributions of the components were also examined. The employed samples were post-processed by hot isostatic pressing (HIP) and heat treatment (HT) at 920 °C for 2 h with and without the application of 100-MPa gas pressure, respectively. The as-built samples consisted of fine acicular α (hcp) microstructures, attributable to the β (bcc) → α' (hcp) martensitic transformation during the EBM process, and these microstructures were coarsened by the HIP and HT processes. However, the fatigue properties of the HIP samples were found to be superior to those of the other samples despite the coarsened microstructure and reduced tensile strength. Notably, a small amount of porosity was observed in the as-built and HT samples, although all the samples were almost fully dense, having relative densities of ~100%. The pores were found to act as crack initiation sites, with the defects having a greater effect on the fatigue properties of the samples than the microstructures. Optimization of the parameters of both the EBM process and the raw powder production process is required to enhance the performance of EBM-fabricated Ti–6Al–4V alloy components.
AB - To establish the benefits of electron beam melting (EBM) for the fabrication of Ti–6Al–4V alloy components, it is necessary to properly understand the fatigue performance of the alloy. In the present study, we investigated the high-cycle fatigue behaviors of EBM-fabricated Ti–6Al–4V alloy component samples and systematically assessed their correlation with the microstructure, porosity, and (quasistatic) tensile properties of the material. The associated texture evolution and elemental distributions of the components were also examined. The employed samples were post-processed by hot isostatic pressing (HIP) and heat treatment (HT) at 920 °C for 2 h with and without the application of 100-MPa gas pressure, respectively. The as-built samples consisted of fine acicular α (hcp) microstructures, attributable to the β (bcc) → α' (hcp) martensitic transformation during the EBM process, and these microstructures were coarsened by the HIP and HT processes. However, the fatigue properties of the HIP samples were found to be superior to those of the other samples despite the coarsened microstructure and reduced tensile strength. Notably, a small amount of porosity was observed in the as-built and HT samples, although all the samples were almost fully dense, having relative densities of ~100%. The pores were found to act as crack initiation sites, with the defects having a greater effect on the fatigue properties of the samples than the microstructures. Optimization of the parameters of both the EBM process and the raw powder production process is required to enhance the performance of EBM-fabricated Ti–6Al–4V alloy components.
KW - Electron beam melting
KW - Fatigue
KW - Microstructure
KW - Porosity
KW - Titanium alloy
UR - http://www.scopus.com/inward/record.url?scp=84999025149&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84999025149&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2016.10.059
DO - 10.1016/j.msea.2016.10.059
M3 - Article
AN - SCOPUS:84999025149
VL - 680
SP - 239
EP - 248
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
ER -