In situ straining deformation of superalloys and intermetallics

Abstract
In situ straining experiments provide the unique advantage of revealing the dynamic behaviour of crystalline defects under the combined effect of stress and temperature. These observations, in real time, allow the understanding and the quantitative analysis of deformation mechanisms. The examples of nickel base superalloys and lamellar TiAl alloys are developed. In these multiphase materials the stresses corresponding to the interface crossing are reached through the formation of pile ups of dislocations which produce at their tip a stress approximately equal to the applied stress multiplied by the number of dislocations involved. When comparing the yield stress of the constituent single phase alloys and the two phase material important differences exist which can be explained in terms of dislocation mobilities.