Abstract
An interfacial CNT-(Mg-6Zn) layer was introduced between SiC particle and Mg-6Zn matrix by a novel method in aim to reduce the excessive thermal residual stresses between SiC particles and matrix. The CNTs were synthesized via CVD on the SiC surfaces, and CNTs kept on the surfaces of SiC particles in the composite during fabrication process. The influence of the interfacial CNT-(Mg-6Zn) layer on the microstructure, the mechanical properties and the Type II thermal residual stresses of composite were investigated with neutron diffraction method. Compared with mono-SiCp reinforced Mg-6Zn composite, the CNTs@SiCp/Mg-6Zn composite presents superior mechanical properties. The E, YTS, UTS and elongation are increased by 9.6%, 14%, 20%, 18.2% respectively. The residual stress of Mg in CNTs@SiCp/Mg-6Zn (35 MPa) is less than half of that (74 MPa) in SiCp/Mg-6Zn composite. Digital image correlation (DIC) investigation indicates that the additional CNTs enhances the bonding strength between SiCp and Mg matrix. The interface layer could release the thermal residual stresses in the composite in two ways: firstly, the gap of the coefficient of thermal expansion (CTE) between the SiCp and the Mg matrix is reduced; secondly, the thermal diffusivity of the composite is declined, leading to lower cooling rate of the as-cast composite in which a portion of residual stresses are released. This work highlights the influence of the interfacial CNT-(Mg-6Zn) layer on the Type II residual stresses and the mechanical properties of the CNTs@SiCp/Mg-6Zn composite.
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