Crystallographic relationship of YTaO4 particles with matrix in Ta-containing 12Cr ODS steel

The crystallography of monoclinic YTaO4 particles and the atomic structure at the particle/ferrite matrix interface in Ta-containing 12Cr ODS steel have been examined by means of SAD and HRTEM. Three different peaks in size distribution of oxide particles were detected by SANS, with the peak positions at 1.5 nm, 9 nm, and 100 nm in size. The results show that many YTaO4 particles are semi-coherent with the matrix, and the habit plane determined in most cases is {051}O//{011}M. Orientation relationships of (051)O//(1¯1¯0)M, [715¯]O//[1¯11]M; (121)O//(110)M, [2¯10]O//[001]M; (051)O//(011)M, [715¯]O//[01¯1]M and (05¯1)O//(1¯1¯0)M, [3¯15]O//[1¯13]M were found. These orientation relationships provide a very small misorientation between the specific planes of YTaO4 particles and {1 1 0} close packed planes of ferrite. Fine particles of around 4 nm in size exhibited incoherent relationship with the misfit angle of around 10° with the matrix. Observation on particles ranging from 7 to 50 nm in size revealed that the crystallographic relationship is semi-coherent between oxide particles and the matrix.