RESIDUAL-STRESSES IN SCS-6 TI-24AL-11NB COMPOSITE .1. EXPERIMENTAL

Residual stress analysis of an as-received and thermally cycled SCS-6/ Ti-24Al-11Nb (at.%) [0]8 metal matrix composite (MMC) was performed us ing the X-ray diffraction (sin2psi) technique. Residual stresses were measured in the alpha2 phase of the matrix in orientations parallel, t ransverse, and 45-degrees to the fiber direction. Stress profiles were determined by successive removal of the matrix from the composite sur face by electropolishing. Within 10 to 30 mum of the first fiber plane , the stress levels were found to be lower than those far from the fib er plane. Residual stress measurements performed on the matrix between the first two fiber rows revealed lower stress levels than those in t he outermost matrix layers. The presence of stress gradients normal to the surface of the composite was also revealed. Measurement of residu al stress levels in the composite subjected to thermal cycling from 15 0-degrees-C to 815-degrees-C in an inert atmosphere revealed almost co mplete stress relaxation after 500 cycles.