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研究了Ti-55钛合金板材在应变速率为8.3×10-4~1.32×10-2 s-1、变形温度885~935℃条件下的超塑性拉伸变形行为和显微组织演化。结果表明:细晶Ti-55钛合金板材表现出良好的超塑性,在温度925℃和应变速率为6.64×10-3 s-1条件下,最大延伸率可达987%,即使在1.32×10-2 s-1的高应变速率条件下也获得了872%的断裂延伸率。在应变速率不变的条件下,变形温度的升高,动态再结晶程度增大,有利于细小等轴的α相晶粒发生相转变。变形速率的不断降低,α相晶粒容易聚集并长大,α相含量减少,β相含量增加,材料塑性反而有所下降。此外,在超塑性变形的过程中,变形区域晶粒长大速度要大于夹头区域,随着变形程度的增大,α相的含量也随之减少,Ti-55材料的变形能够促使晶粒的聚合长大和α相的相转变。
The superplastic tensile deformation behavior and microstructure evolution of Ti-55 titanium alloy sheet under the condition of strain rate of 8.3 × 10-4 ~ 1.32 × 10-2 s-1 and deformation temperature of 885 ~ 935 ℃ were studied. The results show that the fine-grained Ti-55 titanium alloy sheet exhibits good superplasticity. Under the condition of temperature 925 ℃ and strain rate 6.64 × 10-3 s-1, the maximum elongation reaches 987%. Even at 1.32 × 10 An elongation at break of 872% was also obtained at a high strain rate of -2 s-1. Under the condition of constant strain rate, the deformation temperature increases and the degree of dynamic recrystallization increases, which is in favor of phase transformation of the fine equiaxed α-phase grains. Deformation rate continues to decrease, α-phase grains tend to aggregate and grow, α-phase content decreased, β-phase content increased, but the plasticity of the material declined. In addition, in the process of superplastic deformation, the grain growth rate in the deformed zone is larger than that in the chuck zone. As the degree of deformation increases, the content of α phase also decreases. The deformation of the Ti-55 material can promote the grain growth Of the polymerization and α phase growth and phase transition.