Thermal residual stresses in NiAl–AlN–Al2O3 composites measured by neutron diffraction

Thermal residual stresses in NiAl–(AlN)Particle–(Al2O3)Fiber composites were measured at room temperature for two Al2O3 fiber volume fractions (5 and 30%) using neutron powder diffraction. Lattice parameters in each phase were obtained by refining diffraction patterns using Rietveld analysis and lattice strains were calculated from changes in their values. By assuming a volume averaged hydrostatic situation, in conjunction with an FE model that was used to infer the initial stresses between NiAl and AlN, the strains were converted into stresses. The tensile residual stresses in the NiAl matrix were 0.2 and 0.6 GPa for the 5 and 30% Al2O3 composites respectively. The compressive residual stress in the AlN dispersion particles decreased from −1.5 to −1.1 GPa as the fiber volume fraction increased from 5 to 30%. The compressive residual stresses in the Al2O3 fibers were −1.7 and −1.3 GPa for the 5 and 30% Al2O3 composites respectively.