Abstract:Microyield behavior of a silicon carbide particles reinforced 2024 aluminum alloy (SiC_p/2024Al composite) was investigated. The results showed that the composites exhibited some types of notable strain relaxation before microyielding when subjected to an applied stress far lower than conventional yield stress. The microyield mechanism was not conformed to the classical linear relation between the applied stress (σ) and square root of plastic strain(ε^1/2p), proposed by Brown N and Lukens K F. Microyield strength could be strongly affected by heat treatment routes. An appropriate aging treatment would significantly increase microyield strength of the SiC_p/2024Al composite, whereas thermal cycling with large upper-lower cyclic temperature interval would lead to deterioration of microyield strength. Finally the effects of microstructures on microyield behavior of the composite were discussed.

Key words: microyield behavior　strain relaxation　SiC_p/2024Al composite