The influence of thermal-mechanical processing on residual stresses in titanium matrix composites

The effects of three distinct thermo-mechanical processes on the residual stress state in a uni-directionally reinforced SCS-6/Ti-6-2-4-2[0]6 titanium-alloy matrix composite were predicted using a finite element model. For comparison the residual stresses were measured using X-ray and neutron diffraction. Reductions in stress were predicted by the models and both experimental techniques recorded a reduction compared to the as-fabricated material. While the numerically predicted trends qualitatively agreed with the neutron measurements quantitative agreement was not achieved. In the longitudinal direction the neutron results showed closer agreement to the calcualtion whereas in the transverse direction the X-ray results did. Nevertheless the changes did correlate with improvement in fatigue lifetimes.