Microstructural analysis of multilayered titanium aluminide sheets fabricated by hot rolling and heat treatment |
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Authors: | Jinkeun Oh W C Lee Sung Gyu Pyo Woojin Park Sunghak Lee Nack J Kim |
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Affiliation: | (1) Present address: Center for Advanced Aerospace Materials, Pohang University of Science and Technology, 790-784 Pohang, Korea;(2) Sheet Products & Process Research Group, Technical Research Laboratories, Kwangyang Works, Pohang Iron and Steel Co., Ltd., 790-785 Pohang, Korea;(3) the Hynix Semiconductor Inc., 467-860 Ichon, Korea;(4) the Advanced Materials Division, Research Institute of Industrial Science and Technology, 790-600 Pohang, Korea;(5) the Center for Advanced Aerospace Materials and the Department of Materials Science and Engineering, Pohang University of Science and Technology, 790-784 Pohang, Korea |
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Abstract: | This study is concerned with the microstructural analysis of multilayered or bulk Ti aluminide sheets fabricated by the self-propagating
high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. Multilayered Ti/Al sheets were prepared by
stacking thin Ti and Al sheets alternately, and a good Ti/Al interfacial bonding was achieved after rolling at 500 °C. When
these sheets were held at 1000 °C, spheroidal TiAl3 phases were formed by the SHS reaction at Ti/Al interfaces and inside Al layers. Microstructural analysis on the hot-rolled,
multilayered Ti/TiAl3 sheets revealed that intermetallic phases such as TiAl2, TiAl, and Ti3Al were formed at Ti/TiAl3 interfaces due to interaction between Ti and TiAl3 and that pores formed in the TiAl3 layer were significantly reduced during hot rolling. When multilayered Ti/Ti aluminide sheets were heat treated at 1000 °C,
Ti3Al, TiAl, and TiAl2 were grown as Ti and TiAl3 were consumed. As the heat treatment proceeded, TiAl grew further, eventually leading to the fabrication of multilayered
sheets composed of Ti3Al and TiAl. Bulk Ti aluminide sheets, having a lamellar structure of Ti3Al and TiAl, instead of multilayered sheets, were also fabricated successfully by heat treatment at 1400 °C. This fabrication
method of the bulk sheets had several advantages over the method by hot forging or rolling of conventional cast Ti aluminides.
From these findings, an idea to fabricate multilayered or bulk Ti aluminide sheets by hot rolling and heat treatment is suggested
as an economical and continuous fabrication method, and the formation and growth mechanisms of interfacial phases are elucidated
in this study. |
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