TY - JOUR
T1 - Build direction dependence of microstructure and high-temperature tensile property of Co-Cr-Mo alloy fabricated by electron beam melting
AU - Sun, Shi Hai
AU - Koizumi, Yuichiro
AU - Kurosu, Shingo
AU - Li, Yun Ping
AU - Matsumoto, Hiroaki
AU - Chiba, Akihiko
N1 - Funding Information:
This research was supported by the Regional Innovation Cluster Program 2010, a Grant-in-Aid for Scientific Research Development, the Cooperation of Innovative Technology and Advanced Research in Evolving Area from Ministry of Education, Culture, Sports, Science and Technology of Japan. It is also supported by a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS), the inter-university cooperative research program and the Integrated Materials Research Center for a Low-Carbon Society (LC-IMR) of the Institute for Materials Research (IMR), Tohoku University, Sendai, Japan.
PY - 2014/2
Y1 - 2014/2
N2 - The microstructures and high-temperature tensile properties of a Co-28Cr-6Mo-0.23C-0.17N alloy fabricated by electron beam melting (EBM) with cylindrical axes deviating from the build direction by 0, 45, 55 and 90 were investigated. The preferred crystal orientations of the γ phase in the as-EBM-built samples with angles of 0, 45, 55 and 90 were near [0 0 1], [1 1 0], [1 1 1] and [1 0 0], respectively. M23C6 precipitates (M = Cr, Mo or Si) were observed to align along the build direction with intervals of around 3 μm. The phase was completely transformed into a single ε-hexagonal close-packed (hcp) phase after aging treatment at 800 C for 24 h, when lamellar colonies of M2N precipitates and the ε-hcp phase appeared in the matrix. Among the samples, the one built with 55 deviation had the highest ultimate tensile strength of 806 MPa at 700 C. The relationship between the microstructure and the build direction dependence of mechanical properties suggested that the conditions of heat treatment to homogenize the microstructure throughout the height of the EBM-built object should be determined by taking into account the thermal history during the post-melt period of the EBM process, especially when the solid-solid transformation is sluggish.
AB - The microstructures and high-temperature tensile properties of a Co-28Cr-6Mo-0.23C-0.17N alloy fabricated by electron beam melting (EBM) with cylindrical axes deviating from the build direction by 0, 45, 55 and 90 were investigated. The preferred crystal orientations of the γ phase in the as-EBM-built samples with angles of 0, 45, 55 and 90 were near [0 0 1], [1 1 0], [1 1 1] and [1 0 0], respectively. M23C6 precipitates (M = Cr, Mo or Si) were observed to align along the build direction with intervals of around 3 μm. The phase was completely transformed into a single ε-hexagonal close-packed (hcp) phase after aging treatment at 800 C for 24 h, when lamellar colonies of M2N precipitates and the ε-hcp phase appeared in the matrix. Among the samples, the one built with 55 deviation had the highest ultimate tensile strength of 806 MPa at 700 C. The relationship between the microstructure and the build direction dependence of mechanical properties suggested that the conditions of heat treatment to homogenize the microstructure throughout the height of the EBM-built object should be determined by taking into account the thermal history during the post-melt period of the EBM process, especially when the solid-solid transformation is sluggish.
KW - Cobalt chromium alloys
KW - Phase transformation
KW - Powder processing
KW - Tensile behavior
KW - Texture
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U2 - 10.1016/j.actamat.2013.10.017
DO - 10.1016/j.actamat.2013.10.017
M3 - Article
AN - SCOPUS:84892372342
VL - 64
SP - 154
EP - 168
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -