| NiO was coated onto the surface of magnesium borate whisker by chemical coating technique. Magnesium whisker reinforced aluminum matrix composite was fabricated by a squeeze casting technique (denoted as NiO-MBOw/Al), and the volume fraction of the reinforcement was 20%, the matrix was 2024Al alloy. The microstructure of the NiO coatings and composites, and the interfacial reaction were studied by use of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction patterns (SADP), and X-ray diffraction (XRD). Mechanical properties of the composites were also studied by tensile tests and hardness tests. Thermal expansion behaviors of the composites were studied using a dilatometer. The relationship between thermal expansion coefficient and thermal mismatch stress was discussed.The NiO coating changed the interfacial state of the composite and the solution treatment has great effects on the interface state of NiO-MBOw/Al composite. The investigation shows that a kind of chemical reaction exits between NiO coating and aluminum during solution treatment, and one type of orientation relationship was found between theγ-Al2O3, the reaction product, and aluminum. The interfacial state of composite is best after solution treatment 0.5 hour. The interfacial reaction between whisker and matrix did not take place during solution treatment in the composite.Solution treatment has great influence upon the tensile strength of composite. The tensile strength of NiO-MBOw/Al composite increases then decreases with the interfacial reaction increasing. The result of tensile strength indicates that the ultimate tensile strength (UTS) of the NiO-MBOw/Al composite is highest among the composites studied after solution treatment 0.5 hour.The studies of thermal expansion behaviors of the composites show that the residual stress relaxation affects greatly the coefficient of thermal expansion (CTE) of the composite.
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