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Powder metallurgy (PM) Al3Zr reinforced aluminum (Al) composites were fabricated by in-situ reaction during spark plasma sintering (SPS) using the pre-mixed Al and zirconium hydride (ZrH2) powders. The diffusion behavior of Al and zirconium (Zr) elements in Al matrix were studied. It was clarified that ZrH2 decomposed at around 773 K and dissolved Zr elements reacted with Al matrix to form Al3Zr layers around ZrH2 particle. Al3Zr compounds grew toward the center of ZrH2 particle due to a faster diffusion rate of Al compared to Zr element. The tribological behavior of the composite material was investigated by using pin-on-disk wear test under lubricated condition. Friction coefficient and wear volume of Al-Al3Zr composite were much lower than those of pure Al. SEM observation and SEM-EDS analysis on wear track of pin and disk specimens were investigated. The sliding surface of SUS304 stainless steel counterpart after wear test showed very slight damages and no seizure phenomenon with the pin specimen. It is concluded that PM Al-Al3Zr composite had a good tribological property and wear resistance due to hard Al3Zr particles dispersed in Al matrix preferentially contacting the counterpart material to prevent the soft Al matrix in direct contact with SUS steel surface. [ABSTRACT FROM AUTHOR]

The constant increase in power and heat flux densities encountered in electronic devices fuels a rising demand for lightweight heat sink materials with suitable thermal properties. In this article, I introduce the thermal conductivity and thermal expansion coefficient (TEC) of discontinuous pitch-based carbon fiber or graphite flake reinforced aluminum (Al) matrix composites with aluminum-silicon alloy (Al-Si) alloy fabricated through hot pressing. The small amount of Al-Si alloy contributed to enhance the sintering process in order to achieve fully-dense composites. Carbon fiber provides the reducing of TEC while the conservation of thermal conductivity and weight of Al. On the other hand, graphite flake enhanced thermal conductivity Al although TEC of Al was constant despite graphite flake addition. It seems that these results were attributed to the graphite sheet bridging close to Al/Graphite flake interface. This simple process using small quantity of Al-Si alloy allows the low-cost fabrication of Al based lightweight heat sink material. [ABSTRACT FROM AUTHOR]