Self-formed pencil-like bulk composite materials consisting of copper alloy and stainless steel
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I. Ohnuma, R. Kainuma, and K. Ishida Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan (Received 5 September 2007; accepted 27 November 2007)
On the basis of the CALPHAD (Calculation of Phase Diagrams) method, the compositional range of stable miscibility gap and volume fractions of the two liquid phases in the Cu–Fe–Cr–Ni system were predicted, which can provide the guidance for design of self-formed composite materials. Based on such information, the self-formed pencil-like bulk composite materials consisting of copper alloy and two kinds of stainless steels were prepared by controlling the compositions of Cu-rich and Fe-rich phases in immiscible liquid system by the conventional casting process. The experimental results are in good agreement with the ones predicted by calculation. This study indicates that it is possible to develop the pencil-like bulk composite materials consisting of copper alloy and stainless steels by the conventional casting process.
I. INTRODUCTION
Cu/Fe composite materials are widely used in many fields because of their optimal combination of the high electrical and thermal conductivities of Cu and lower thermal expansivity and higher strength of Fe. For example, the bonding between stainless steel and copper is applied in heat exchangers and safes, where the heat conductivity of copper and corrosion resistance of the stainless steel are required.1–4 However, it is difficult to fabricate the Cu/Fe composite materials by the conventional composite process because of the poor wetting between Cu and Fe.5 Recently, the present authors developed the core-type composite powders and bulk ingots in the Cu–Fe base alloys by means of the conventional gas atomization6 and solidification method,7 respectively, which indicate that the core-type powders and bulk ingots in the Cu–Fe base alloy system can be obtained by the Marangoni effect8 if the temperature gradient is large enough even under the conventional casting process, and the sequence of the phases in the core and periphery parts can be controlled by changing the volume fractions of two liquid phases. Results showed that it is a simple process for developing
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0137 J. Mater. Res., Vol. 23, No. 4, Apr 2008
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the practical composite materials with the combination of different properties. The Calculation of Phase Diagrams (CALPHAD) method has been recognized to be an important tool in the design of materials.9 Recently, the present authors developed a thermodynamic database for Cu-based alloys in the framework of the CALPHAD method,10,11 which can provide much information for the design of such composite materials. The purpose of the present study is to design the compositions of self-formed composite materials consisting of copper alloy and the stainless steels with the aid of calculation of phase diagrams and then to fabricate the pencil-like
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