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。
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.
出处
《机械工程材料》
CAS
CSCD
1990年第6期5-8,33,57,共6页
Materials For Mechanical Engineering
