Aging behavior of 6061Al matrix composite reinforced with high content SiC nanowires

The aging behavior of Al matrix composites reinforced with high content nano-reinforcements has been rarely reported. In the present work, the aging behavior of 15 vol.% SiCnw/6061Al composite prepared by pressure infiltration method has been investigated. GP zones, β″ (Mg5Si6) and B′ (MgSi>1) were observed as the main precipitates in under-aged, peak-aged and over-aged SiCnw/6061Al composite, respectively. After addition of high content SiC nanowires, the precipitation sequence of 6061Al has changed from “GP zones → β″ (Mg5Si6) → β′ (Mg1.8Si) → β (Mg2Si)” to “GP zones → β″ (Mg5Si6) → B′ (MgSi>1)”. Due to their higher surface energy and larger surface areas of SiC nanowires, the segregation of Mg element is very serious, leading to insufficient Mg amount to form high Mg precipitates. Moreover, the hardness of SiCnw/6061Al composite was decreased much faster than that of 6061Al alloy in the over-aging period, which might be due to the inferior strengthening effect and/or low dispersivity of B′ phase. [Display omitted] •Aging behavior of 15 vol.% SiCnw/6061Al composite was investigated.•Aging sequence of SiCnw/6061Al composite was “GP zones → β″ (Mg5Si6) → B′ (MgSi>1)”.•Segregation of Mg at interface leads to insufficient Mg to form high Mg precipitates.