REAL TIME IN SITU X-RAY DIFFRACTION STUDY OF THE HIGH TEMPERATURE MECHANICAL BEHAVIOR OF A RAFTED SINGLE CRYSTAL SUPERALLOY

摘要

During high temperature creep or more complicated tests requires data on the actual volume fraction of Gamma Prime phase, as well as the internal stress state and plastic strain of each phase, mobile dislocation densities... This can be obtained at a few minutes intervals by a combination of high resolution synchrotron XRD at the high energy beamlines of the ESRF or DESY and in situ HT mechanical testing. We present here experimental results obtained during tests between 950°C and 1160°C involving either stress jumps or temperature excursions. In both cases, the Gamma corridors exhibit a threshold behaviour related to the Orowan stress. The strain rate of the Gamma Prime rafts does not only depend on the applied load, but even more on the actual value of the stress component perpendicular to the tensile axis.