Effect of silicon additions on characteristics of carbon fiber reinforced aluminum composites during thermal exposure
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Effect of silicon additions on characteristics of carbon fiber reinforced aluminum composites during thermal exposure Hui-Ming Chenga) and Ben-Lian Zhou International Center for Materials Physics, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110015, China
Akira Kitahara and Shigeru Akiyama Government Industrial Research Institute-Kyushu, AIST, MITI, Saga 841, Japan
Kazuo Kobayashi Department of Materials Science and Engineering, Nagasaki University, Nagasaki 852, Japan (Received 24 February 1995; accepted 15 January 1996)
The effects of Si additions on the behavior of high modulus carbon fiber reinforced aluminum matrix (CFyAl) composites during thermal exposure at 773 K for different times have been investigated. The composites were fabricated via hybridization with a small volume fraction of SiC particles using a pressure-casting process. The change of longitudinal tensile strength, the strength degradation of carbon fibers, and the microstructural observations on the interfaces of CFypure Al composites and CFyAl–Si composites after thermal exposure undoubtedly indicate that the alloying element Si in an aluminum matrix can effectively prohibit the interfacial reactions at the fiber/aluminum interface and has positive effects on the characteristics of CFyAl composites.
I. INTRODUCTION
Carbon fiber reinforced aluminum (CFyAl) composite materials have been developed to offer promising properties, including high tensile strength and stiffness, improved fatigue life, high-temperature mechanical properties, and excellent thermophysical properties. However, most of these properties, particularly the strength properties, strongly depend on the interfacial properties of CFyAl composites, such as interfacial bonding and interfacial chemical interactions between carbon fibers and aluminum matrices. It is known that, though the properties of CFyAl composites may be excellent at ambient temperatures, in most cases, they are disappointing at elevated temperatures.1 Therefore, it is most important to understand the characteristics and behavior of CFyAl composites during and after thermal exposure at elevated temperatures. Only little research work has been presented on the fiber degradation of CFyAl composites and the strength change of CFyAl composites after thermal exposure.2–6 The present authors have reported the changes in strength and fracture mode of carbon fiber reinforced aluminumsilicon matrix (CFyAl –Si) composites during thermal exposure at 773 K.2 It was found that the longitudinal tensile strength of the composites increased, though the degree was small, up to the thermal exposure time of 216 h, then decreased as the thermal exposure time was prolonged. These results suggested that CFyAl–Si a)
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J. Mater. Res., Vol. 11, No. 5, May 1996
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composites could have a relatively long lifetime when they were to be used b
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