Recrystallisation of single crystal superalloy CMSX-4

A series of experiments investigating the recrystallisation of single crystal superalloy CMSX-4 have been carried out. Indentation at room temperature has been used to study the effects of annealing time and temperature, and it has been found that a very strong dependence upon temperature is evident. Annealing above the gamma' solvus temperature results in very rapid growth of recrystallised grains whereas annealing below the gamma' solvus greatly suppresses the advancing grain boundaries. Additionally experiments have been carried out using an electrothermal mechanical test (ETMT) machine, to study the effects of degree of plastic strain and the temperature at which the strain is introduced. The strain threshold for recrystallisation under various annealing conditions has been determined and it has been found that recrystallisation occurs more readily if strain is introduced above 950degreesC. Finally, apparent activation energies for recrystallisation have been determined by measuring the change in resistivity that occurs during recrystallisation.