Effect of networked Cu-rich ferrite phase on proof stress and ultimate tensile strength of sintered bodies of Fe–Cu hybrid-alloyed steel powder with graphite

ABSTRACT

To improve the yield strength of powder metallurgy steel, this work investigated the effect of a Cu-rich networked phase. Mixtures of 0.7% graphite and Fe–3% Cu hybrid-alloyed steel powders, composed of pre-alloyed Fe–3 x % Cu particles with diffusion-bonded 3(1 − x) % Cu (0 ≤ x ≤ 1), were processed by high-density compaction and conventional sintering. The maximum values of 0.2% proof stress (YS) and ultimate tensile strength (UTS) were obtained at x = 0.68, where high-density compact with well-networked Cu-rich ferrite phase was developed without Cu growth. Moreover, nanosized ϵ-Cu precipitates were observed in the Cu-rich ferrite. These high YS and UTS were achieved not only by decreases in porosity but also by precipitation strengthening caused by the nanosized ϵ-Cu in the Cu-rich ferrite network.

KEYWORDS:

• Cu hybrid-alloyed steel powder
• proof stress
• tensile strength
• Cu-rich ferrite network
• precipitation strengthening
• nanosized ϵ-Cu precipitates

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Y. Shigeta

Y. Shigeta is a student of the Department of Materials Physics and Chemistry, the Graduate School of Engineering, Kyushu University. He joined the group of Professor Ozaki, who has investigated the microstructures of sintered steels. He won the best presentation prize at the annual meeting of the Japanese Society of Powder and Powder Metallurgy (2020).

M. Aramaki

M. Aramaki is an Assistant Professor in the Department of Materials Science and Engineering at Kyushu University Japan. He received his Ph.D. from the Faculty of Engineering at Kyushu University focusing attention on aspects of superplastic phenomenon in steels. He studies a variety of areas pertinent to the strength and ductility of metallic materials. He also conducts research in the field of plastic working such as automotive parts. He was an editorial board member for the Journal of the Japan Society for Technology of Plasticity.

K. Ashizuka

K. Ashizuka obtained the D. Eng. degree in 2013 from the Department of Material Science and Engineering, Kyushu University, Japan. He is currently a senior researcher for Steel Research Laboratory, JFE Steel Corporation.His research focuses on the study of development of alloyed steel powders for high strength sintered machine parts.

Y. Ikoma

Y. Ikoma is an Assistant Professor in the Department of Materials Science and Engineering at Kyushu University, Japan. He received his Dr. Eng. degree from the Faculty of Engineering at Kyushu University, in 1999. His main research area is formation of nanostructured semiconductor materials obtained by various methods, such as chemical vapor deposition and severe plastic deformation. He is also involved in microstructure characterization of semiconductor and metallic materials using transmission electron microscopy.

Y. Ozaki

Y. Ozaki received the D.Sc. degrees from Hokkaido University, Sapporo, Japan, in 1987. She joined Kawasaki Steel Corporation (JFE Steel Corporation), Tokyo, Japan, in 1988. Since 2016, she has been with the Department of Material Science and Engineering, Kyushu University, where she is currently a Professor. Her main areas of research interest are consolidation mechanisms of metallic powder including metallic glasses, and microstructural control of sintered alloy steels.Dr. Ozaki is a member of several societies such as the Japanese Institute of Metals and Materials (JIM), the Iron and Steel Institute of Japan (ISIJ), and European Powder Metallurgy Association. She is also a member of the Science Council of Japan since 2014.