STUDY OF THE BRITTLE-TO-DUCTILE TRANSITION IN NIAL BY TEXTURE ANALYSIS

Polycrystalline NiAl displays a brittle-to-ductile transition temperat ure (BDTT) at the relatively low temperature of 0.3 T-m. Explanations of the low BDTT generally suffer from uncertainties in measuring bulk deformation mechanisms in post-deformation thin foils. Therefore, the present study emphasizes the bulk measurement of deformation mechanism s by interpretation of experimental and computer simulated textures. W hile NiAl develops a {110} fiber texture during elevated temperature e xtrusion, subsequent uniaxial deformation of NiAl below the recrystall ization temperature results in no texture evolution. This can only occ ur if the active deformation mechanisms produce no crystal rotation, c onsistent with the reported [100]{011} slip system. Activation of any secondary slip system must cause lattice rotation, manifest by a chang e in texture. These results suggest that no additional slip systems ar e activated at the BDTT in polycrystalline NiAl and that diffusional p rocesses are responsible for the increased plasticity.