The Al-Si-Cu alloy matrix composite reinforced by aluminum borate whisker with NiO coating was fabricated by squeeze casting. The effects of T4 treatment on the microstructure, tensile strength, and hot rolling behavior of the composite were investigated. During T4 treatment, the NiO coating on whisker surface can react with aluminum matrix in the composite. The ultimate tensile strength of unrolled composite can be enhanced through T4 treatment at 490 degrees C, which is considered as the results of interfacial reaction. The hot-rolled composite without pre-T4 treatment exhibits much higher ultimate tensile strength than the hot-rolled composite with pre-T4 treatment, and the ultimate tensile strength of hot-rolled composite without pre-T4 treatment can be enhanced through subsequent T4 treatment after hot rolling. The effect mechanism of T4 treatment on the tensile strength of the composite was discussed in the study. (c) 2005 Elsevier B.V. All rights reserved.