A Cu-ZrW2O8 metal matrix composite was cooled from 573 K to room temperature while being subjected to X-ray diffraction in transmission using high-intensity synchrotron radiation. During cooling from high temperature, the thermal expansion mismatch between the copper matrix and the ceramic particles was investigated. The stress development due to the thermal mismatch was followed by lattice strain variation of copper matrix. The lattice strain of copper matrix determined from the measured diffracted ring radiuses, and the thermal expansion behavior of the metal matrix. The phase pressures (average hydrostatic stresses in the constituent phases of metal matrix composite) were predicted. The magnitude of hydrostatic pressure on ceramic particles was found to be sufficient enough to produce the pressure-induced phase transformation in ZrW2O8 phase. (C) 2002 Elsevier Science Ltd. All rights reserved.