On the coherency of Y2Ti2O7 particles with austenitic matrix of oxide dispersion strengthened steel

Coherency and orientation relationship of nano-sized Y2Ti2O7 particles with an austenitic matrix of oxide dispersion strengthened steel was investigated using selected area diffraction contrast techniques and high resolution transmission electron microscopy. It was revealed that over 95% of the Y2Ti2O7 particles (3-10 nm in diameter) are semi-coherent with the austenitic matrix. Perfectly matched planes, which produce no-contrast lines under proper two-beam conditions in transmission electron microscopy (TEM), were obtained across the oxide/matrix interface between parallel planes of 2‾20Y2Ti2O7//200Matrix, and 3‾3‾1Y2Ti2O7//02‾2Matrix. A single no-contrast line and multiple no-contrast lines under different active g-vectors were observed and discussed. The lattice distortion in the matrix around the Y2Ti2O7 particles was determined using the diffraction contrast method under TEM and through X-ray diffraction analyses, which revealed good agreement. A decrease in the inter-planar spacing of up to 7.5% was detected in 02‾2Matrix planes owing to the misfit strain at the oxide/matrix interface.