The recrystallization behavior of surface deformation layer of (TiB+TiC)/Ti-6Al-4V composite during isothermal annealing

The recrystallization behavior of surface deformation layer of (TiB. +. TiC)/Ti-6Al-4V and Ti-6Al-4V were both investigated during isothermal annealing using X-ray diffraction line profile analysis. The surface deformation layer was introduced by shot peening treatment. The results revealed that with increasing the time of isothermal annealing, the microstructure variations at shot peened layer were obvious. Based on the results of line profile analysis, the recrystallization activation energies were calculated by computer regression analysis, and it showed that the recrystallization activation energy of (TiB. +. TiC)/Ti-6Al-4V was larger than that of Ti-6Al-4V, which was ascribed to the effect of reinforcements hindering the movements of dislocations, grain and subgrain boundaries in the process of recrystallization. The hindrance effect of reinforcements as sink sources of dislocations gliding resulted that the decrease rate of dislocation density of the composite was slower than that of the matrix. In addition, the relaxation activation energies were obtained according to the analysis of microstrain relaxation, and after isothermal annealing, the depth distribution of domain sizes from the top surface was investigated and discussed in detail. According to above analysis, the results showed that the thermostability of the composite was higher than that of the matrix because of the effect of reinforcements. © 2011 Elsevier B.V.