Texture evolution in NiAl

We have investigated texture evolution in stoichiometric NiAl and Ni-49at.%Al–1at.%Ti using orientation imaging microscopy (OIM) and X-ray diffraction. Grain size and orientation were studied after extrusion and after heat treatment, leading to the following model of texture evolution. During extrusion, dynamic recrystallization occurs with a continuing cycle of deformation to produce a 〈110〉 fiber texture, nucleation of nearly randomly-oriented grains, and preferential growth of 〈111〉 grains. Upon cooling from the extrusion temperature, nucleation continues until the temperature drops below the recrystallization temperature. A 〈110〉 fiber texture observed after extrusion suggests the specimen did not fully recrystallize during cooling and the deformation texture is retained. A 〈111〉 fiber texture indicates a fully recrystallized microstructure in which significant grain growth has occurred. It has been found that titanium addition increases the recrystallization temperature of NiAl and retards grain growth resulting in the retention of the 〈110〉 fiber texture.