Evolution of dislocation structure in the heat affected zone of a nickel-based single crystal

Using polychromatic microbeam synchrotron diffraction together with electron and optical microscopy, we studied dislocation structure changes of Ni-based single crystal superalloy during impulse heating up to the melting temperature. It is shown that the distribution of the thermal gradient is not monotonic. The maximum value of the thermal gradient is observed in the heat affected zone near the fusion line. Depending on the temperature, the formation of dislocation is accompanied by the partial or complete dissolution of gamma' particles in the matrix. Dislocations form and multiply due to thermal gradients, and their arrangement correlates with temperature gradient field and with the dissolution and reprecipitation of gamma' particles. (C) 2004 American Institute of Physics.