EBSD study on dual heat treatment and microstructure evolution of TA15 titanium alloy

The study of dual heat treatment with different parameters has been performed on TA15 titanium alloy, which is a typical near α ?titanium and widely used in aerospace. The Electronic backscatter diffraction (EBSD) technique has been employed to characterize the microstructure and analyze the crystal orientation distribution of those samples subjected to different heat treatment. The effect of the heat holding time on microstructure morphology and orientation distribution was investigated. The formation and evolution of equiaxed primary α_p, lamellar second? α_s and transformed? β_T during the process of dual heat treatment has been revealed. The crystal orientation relationship between the α_p and adjacent α_s has been analyzed. The results indicate that the holding time of stage I has an obvious influence on the morphology and distribution of α_p. The equiaxed α_p comes from heat treatment stage I as a result of retained primary α_p. The holding time of stage II has a significant effect on the size and morphology of α_s. The mode of first lengthening and then thickening has been observed during the α_s coarsening process. A certain degree of match has been found between the crystal orientation of α_p and adjacent α_s.