Grain growth in the nanocrystalline W-Cu and Cu-Pb composite powders prepared by mechanical alloying

The thermal behavior of the nanocrystalline W-Cu and Cu-Pb powders was inve stigated in order to gain thermal stability information for further applica tion and also to elucidate the grain growth kinetics in an immiscible alloy system. The nanocrystalline alloy powders were prepared by mechanical allo ying (MA) and characterized. Thermal behavior of this nanocrystalline alloy was analysed by DSC, XRD, SEM, TEM and EXAFS. The time exponent n and the activation energy for grain growth were determined from the grain size data . The nanocrystalline W, Cu and Pb have revealed lower n values than the po lycrystalline ones. The activation energy of the nanocrystalline W, Cu, and Pb grain growth in MAW-Cu and Cu-Pb powders is 186.5 +/- 1.0, 55.6 +/- 10. 5 and 42.0 +/- 3.9 kJ/mol, respectively. The melting point suppression of P b crystalline embedded in Cu matrix in MA Cu-Pb powders can be estimated. O n the basis of the grain growth parameter obtained in this study and availa ble data in the literature, the grain growth features and kinetics in the n onequilibrium state of the immiscible alloy system are discussed.