Effect of HIP Temperature and Post-HIP Heat Treatments on Coincidence Site Lattices and Twin Boundaries in IN718

摘要

Electron back scattered diffraction has been used to determine the effect of HIPping (Hot Isostatically Pressing) at different temperatures on grain size and on the fraction of Σ3 twin boundaries in as-HIPped IN718 powder and in HIPped samples which have been subsequently heat treated. Tensile tests have been carried out on these samples. It has been found that the highest fraction of Σ3 boundaries was present in the coarser grained samples and this increase in the fraction of Σ3 boundaries is associated with higher ductility at both room temperature and at 650 ℃. Transmission electron microscopy (TEM) has been used to assess changes in precipitate sizes caused by these heat treatments, which also influence tensile properties.