Strain-induced symmetry breakdown in HOLZ lines from L1(2) titanium tri-aluminides

Energy filtered CBED patterns of the Cr-stabilized Lit phase of a titanium tri-aluminide alloy reveal deficit higher order Laue zone (HOLZ) lines in t he zeroth order diffraction disk, for which the expected 4-mm symmetry is s ignificantly broken in the < 001 > projection. This apparent break of symme try may be explained by the presence of lattice strains of order 10(-3). Ef fects of strain-induced lattice distortions on HOLZ line symmetries are cal culated by an introduction of rhombohedral, tetragonal or monoclinic distor tions to the cubic unit cell. It is shown how tensile and shear components of strain affect the overall HOLZ line symmetries in different ways.