Local stress modification during in situ transmission electron microscopy straining experiments

The stress distribution in a foil strained in situ in a transmission electron microscope is strongly affected by the polished depression and the hole. In the present study, this effect has been investigated in detail on a Fe–Si foil plastically deformed under uniaxial straining in transmission electron microscopy. The slip-trace direction varied considerably around the hole, indicating local changes of the macroscopic slip plane. Since non-crystallographic slip occurs in Fe–Si under conditions used in the experiment and the crystallographic relation between the macroscopic slip plane and the tensile stress direction is known, the local tensile axes could be established. It was found that the deviations of the local tensile stress axis from the external stress axis may be as large as ±60°. The stress distribution determined experimentally is compared with an analytical solution as well as a finite element analysis of the problem.