Effect of Microstructure and Precipitate on Tensile Properties of V-5Cr-5Ti Alloy

After homogenization, forging, cold rolling, and recrystallization of V-5Cr-5Ti alloy, universal testing machine, scanning electron microscopy, and transmission electron microscopy were used to study the effect of precipitates on the mechanical properties of the alloy and to estimate the strengthening effect. Results show that as-cast V-5Cr-5Ti alloy has a dendritic structure characterized by lamellar phase. After homogenization, the precipitates are transformed from a lamellar to a needle-like dendritic structure. The precipitates are broken into a short-bar or spherical phase during forging and cold rolling. The average tensile strength, yield strength, and elongation of the as-cast alloy are 505.0 MPa, 415.0 MPa, and 8.2%, respectively, with the brittle cleavage fracture as the dominant fracture mechanism. The fracture mechanism is transformed into a mixed fracturing mode of intergranular and quasidissociative fractures after homogenization. After 80% cold rolling and 1000 degrees C/1 h annealing, the average tensile strength, yield strength, and elongation of the alloy are 487.3 MPa, 382.7 MPa, and 26.2%. The alloy plasticity is greatly improved due to the refinement of the grain and precipitates. The fracture mechanism of the alloy after cold rolling and annealing is microporosity fracture. The precipitates enhance V-5Cr-5Ti alloy by Orowan strengthening mechanism. Taking the alloy after 80% cold rolling and annealing at 1000 degrees C/1 h as an example, the yield strength increment obtained by precipitate strengthening is about 50.1 MPa.