Sung-Kil Hong, Jung-Chul Choi, De-Zhung Lin,Hiroyasu Tezuka, Tatuo Sato and Akihiko Kamio
Department of Metallurgical Engineering, Tokyo Institute of Technology, Tokyo
Precipitation sequences of the age hardenable aluminum alloy composites are strongly affected by the dislocations generated during quenching from the solution treatment temperature. In this study, age hardening behavior of Al-4 mass%Cu and Al-4 mass%Cu-1.5 mass%Mg base composites reinforced with SiC whisker (SiCw) was investigated with micro-Vickers hardness measurement, differential scanning calorimetry and transmission electron microscopy. SiCw/Al-Cu and SiCw/Al-Cu-Mg composites indicate a remarkable age hardening in spite of the suppression of the G.P. zone or G.P.B. zone formation rate, and the age hardening rate is accelerated. In particular, age hardening of the SiCw/Al-Cu-Mg composite is larger than that of the unreinforced alloy. The precipitation process of the SiCw/Al-Cu composite is different from that of the unreinforced alloy. Many metastable θ′ phases (Al2Cu) precipitate preferentially on dislocations in the matrix prior to G.P. zone and contribute for the age hardening of the composite, but the posteriorly formed G.P. zone still plays the most important role in the hardness increase. In the case of the SiCw/Al-Cu-Mg composite, the age hardness steeply increases with the formation of the G.P.B. zone at the initial stage and decreases temporarily and then increases again due to the precipitation of a fine and high dense S′ (Al2CuMg) phase.
(Received September 13, 1995)
precipitation sequence, SiC whisker/aluminum-copper, SiC whisker/aluminum-copper-magnesium, age hardening behavior, differential scanning calorimetry, transmission electron microscopy
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