Three Cu-TiB2 alloys (0.45, 1.6, 2.5 wt.% TiB2) have been prepared by a combination of in situ reaction and rapid solidification under optimized conditions. The relationship between microstructure, properties and in situ reaction condition for these Cu-TiB2 alloys was investigated and analyzed by modeling. It is shown that the distribution and size of TiB2 particles are strongly dependent on the choice of in situ reaction conditions and solute concentration; specifically, the size and aggregation level of TiB2 particles tend to increase as the volume per cent of TiB2 in the three Cu-TiB2 alloys increases when the same in situ reaction conditions are used. The forming, coarsening and aggregation models of TiB2 particles are established. The mechanical properties of three Cu-TiB2 alloys are directly related to the distribution and size of TiB2 particles, the change in the grain size and the residual solute concentration. A composite model reveals the separate contributions of these parameters to the mechanical properties. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.