Isothermal γ →ε phase transformation behavior in a Co-Cr-Mo alloy depending on thermal history during electron beam powder-bed additive manufacturing
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2020年第15期
论文作者：Yufan Zhao Yuichiro Koizumi Kenta Aoyagi Kenta Yamanaka Akihiko Chiba
文章页码：162 - 170
摘 要：Powder bed fusion with electron beam（PBF-EB）,allows Co-Cr-Mo（CCM） implants with patientcustomization to be fabricated with high quality and complex geometry.However,the variability in the properties of PBF-EB-built CCM alloy,mainly due to the lack of understanding of the mechanisms that govern microstructural heterogeneity,brings limitations in extensive application.In this study,the microstructural heterogeneity regarding the γ-fcc→ε-hcp phase transformation was characterized.The phase transformation during PBF-EB was analyzed depending on the thermal history that was elucidated by the numerical simulation.It revealed that isothermal γ→ε transformation occurred during the fabrication.Importantly,the difference in γ/ε phase distribution was a result of the thermal history determining which method phase transformation was taking place,which can be influenced by the PBF-EB process parameters.In the sample with a low energy input(Earea=2.6 J/mm2),the martensitic transformation was dominant.As the building height increased from the bottom,the e phase fraction decreased.On the other hand,in the sample with a higher energy input(Earea=4.4 J/mm2),the ε phase fo rmed via diffusional-massive transformation and only appea red in a short range of the lower part away from the bottom.
Yufan Zhao1，Yuichiro Koizumi2，Kenta Aoyagi2，Kenta Yamanaka2，Akihiko Chiba2
1. Department of Materials Processing, Graduate School of Engineering, Tohoku University2. Institute for Materials Research, Tohoku University
摘 要：Powder bed fusion with electron beam（PBF-EB）,allows Co-Cr-Mo（CCM） implants with patientcustomization to be fabricated with high quality and complex geometry.However,the variability in the properties of PBF-EB-built CCM alloy,mainly due to the lack of understanding of the mechanisms that govern microstructural heterogeneity,brings limitations in extensive application.In this study,the microstructural heterogeneity regarding the γ-fcc→ε-hcp phase transformation was characterized.The phase transformation during PBF-EB was analyzed depending on the thermal history that was elucidated by the numerical simulation.It revealed that isothermal γ→ε transformation occurred during the fabrication.Importantly,the difference in γ/ε phase distribution was a result of the thermal history determining which method phase transformation was taking place,which can be influenced by the PBF-EB process parameters.In the sample with a low energy input(Earea=2.6 J/mm2),the martensitic transformation was dominant.As the building height increased from the bottom,the e phase fraction decreased.On the other hand,in the sample with a higher energy input(Earea=4.4 J/mm2),the ε phase fo rmed via diffusional-massive transformation and only appea red in a short range of the lower part away from the bottom.
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