The effect of different oxide particles on the microstructure and the high temperature creep behavior of ODS ternary L12-(Al,Cr)3Ti intermetallic compounds, which were prepared by high energy ball milling, was analyzed. Particular attention was paid to the development of the dispersoid size and distribution after the milling process, the consolidation and the heat treatment.
X-ray diffraction (XRD) and transmission electron microscopy (TEM) of the as-milled powders indicate that the ordered matrix can nearly be amorphizied during milling. Moreover, independent of the type of oxide the dispersoids with a mean diameter ≤ 20 nm are homogeneously distributed in the metallic matrix. Using hot pressing under protective atmosphere the powders were compacted to nearly full density, followed by heat treatment. This results in grain sizes varying between 200 nanometers and several micrometers. However, due to the nature of the dispersoids used different particle diameters were found after consolidation and annealing. Although known to be the thermodynamically most stable oxide the initial Y2O3 powder has formed a mixed yttrium-aluminum oxide during manufacturing and, hence, significant particle growth has been observed. While CeO2 shows a similar behavior, the line compound A12O3 remains stable, but the average particle size of this oxide also increases during the heat treatment. First preliminary mechanical tests supported by TEM observations show the significant influence of the grain size on the creep resistance at high temperatures.