新型高强韧Ti-Al-Fe-B系钛合金组织和性能研究

Effect of Al element addition (1wt%~3wt%) and heat treatment on microstructure evolution and mechanical property of a new alloy Ti-xAl-3.5Fe-0.1B was studied. Results indicate that Ti-xAl-3.5Fe-0.1B is α+β two-phase titanium alloy. Yield strength of the alloy increased from 590 MPa to 900 MPa and tensile strength increased from 808 MPa to 1074 MPa with the variation of Al element from 1% to 3% due to solid solution strengthening effect; at the same time, the elongation decreased to 15.4%. Microstructure observation reveals that the thickness of the lamellar primary α phase was reduced and the grain size was remarkably refined with the increasing Al element content. Meanwhile, it is found that yield strength continuously increased to 1000 MPa, tensile strength increased to 1144 MPa and the elongation increased to 17.5% after double annealing, which indicates unique mechanical property. The metastable β phase formed in the microstructure was decomposed to secondary α phase with fine grain size during the double annealing in the alloy, which blocked the movement of dislocation and induced enhancement of strength. At the same time, the dispersion of secondary α phase on β substrate was also beneficial to the strength. On the other hand, the presence of equiaxed α phase was considered favorable to the improvement of elongation.