Effect of Mg Content on the Thermodynamics of Interface Reaction in C f /Al Composite
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CONTINUOUS carbon-fiber-reinforced aluminum matrix composites (Cf/Al) have received considerable attention because of their high specific strength and modulus for application in the aerospace industry.[1] The carbon–aluminum (C-Al) interface plays a crucial role in the properties of the Cf/Al composite.[2] Unfortunately, the interfacial reaction between carbon fiber and Al matrix is severe above 773 K (500 C).[3] Yang et al.[4] observed that the growth mechanism of Al4C3 at the carbon–aluminum (C-Al) interface was vertical at a low temperature (981 K [708 C]) and lateral at higher temperature (1021 K [748 C]). It is evident that this large and excessive interfacial reactant, aluminum carbide (Al4C3), is detrimental to their mechanical properties.[5,6]
CHENCHONG WANG, Postgraduate Student, GUOQIN CHEN, Associate Professor, and GAOHUI WU, Professer, are with the School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, P.R. China. Contact e-mail: [email protected] XU WANG, Researcher, is with the School of Mechanical Engineering, Liaoning Shihua University, Fushun 113001, P.R. China. YUNHE ZHANG, Associate Professor, is with the School of Electromechanical Engineering, Northeast Forestry University, Harbin 150040, P.R. China. WENSHU YANG, Postgraduate Student, is with the School of Materials Science and Engineering, Harbin Institute of Technology and with the Department of Materials Science and Chemical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy. Manuscript submitted August 25, 2011. Article published online February 22, 2012 2514—VOLUME 43A, JULY 2012
Many methods have been developed to control the unfavorable interfacial reaction, such as the modification of C fiber (selection of fiber types[7,8] and fiber surface modification[9,10]) and Al matrix (addition of alloying element[11,12]). Zhang et al.[7] compared T700 carbon fiber and M40 graphite fiber and found that less and smaller Al4C3 was observed in the M40f/Al composite as a result of the higher graphitization of M40 fiber. Although the strength of the M40 fiber (4.4 GPa) was slightly lower than that of the T700 fiber (4.9 GPa), the tensile strength of M40f/Al composite (750 MPa) was twice than that of the T700f/Al composite (380 MPa).[7] Daoud[9] used Ni-coated fibers to reinforce the 2014Al alloy and no significant Al4C3 was detected. However, the coating treatment makes the preparation of a Cf/Al composite more complex and expensive.[13] The alloying treatment seems to be a simple and cheap method to modify the interfacial structure and improve the properties of the matrix alloy.[14] It has been observed that the addition of Mg could improve the infiltration process[11] and mechanical properties.[12] The critical value of the Mg content for undetectable formation of Al4C3 phase was 8.5 wt pct.[12] It is supposed that the formation of b phase (Al3Mg2) at the C-Al interface inhibits the growth of Al4C3. However, the theoretic mechanism of Mg effect has not been explained. The componen
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