【摘要】 研究了Ti-6 Al-4 V合金的拉伸塑性（ψ）和显微组织对其断裂韧性(K_lc)及裂纹扩展速率（da/dN）的影响。结果表明,魏氏组织合金的β原始晶粒度D_β与ψ呈反比关系。D_β<440μm,α片厚度b=-2.5～3.5μm时,K_lc最高。K_lc及da/dN与ψ的关系与组织类型有关,随ψ增大,K_lc升高,达到一定数值后,对于魏氏组织,K_lc不再变化,对于等轴组织,则K_lc下降。魏氏组织及等轴组织的da/dN-ψ关系曲线上均有极小值。与空冷退火相比,淬火时效能显著降低合金的da/dN。进行990℃,1h,W.O.+950℃,20h-A.C.处理,能获得最佳K_lc及da/dN。更多还原

【Abstract】 In this paper we researched the influence of tensile ductility （ψ） and microstructure of Ti-6 Al-4 V alloy on its fracture toughness (K_lc) and crack propagation（da/dN）. The results show that ψ of Ti-6 Al-4 V alloy is an inverse measure of prior β grain size D_s. when thickness of a platelets （b） is in the range of 2.5～3.5μm and D_β<440μm, the K_lc of the alloy possesses maximum value. The relations of K_lc and da/dN with ψ are dependent on the microstructure type of alloy, K_lc increases with increase of ψ, and then becomes invariable for Widmanstuten structure, but for equiaxed structure it increases at first with increase of ψ, and then decreases. Relative to da/dN, with increase of ψ it changes along a curve with miuimum both for Widmanstutten and equiaxial structure. The da/dN of Widmanstutten structure are controlled by b. The da/dN of alloy heattreated by water quenching + aging are obviously slower than that heattreated by air cooling annealing. Optimum K_lc and da/dN ca be obtained by the following heat treatment. 990℃, 1h W. Q. + 950℃, 20h A. C.更多还原