Ti-8Al-1Mo-1V 合金の破壊靱性

概要

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Effect of microstructure on fracture toughness of a near α Ti-8Al-1Mo-1V alloy was systematically examined. At 0℃, β-processed specimens with acicular microstructure had higher fracture toughness at a given strength than those with equiaxed microstructure, because the former had a greater crack extension resistance than the latter. The embrittling phase, α_2 phase, which precipitated during furnace cooling after annealed at 650∿950℃, reduced fracture toughness by more than 20 percent although that increased tensile strength. Precipitation of α_2 phase had a great influence on crack initiation and reduced CTOD value at crack initiation, δ_i, by 50 percent. At -196℃, the specimens with acicular microstructure had higher fracture toughness than those with equiaxed microstructure similar to those tested at 0℃. The latter had lower fracture toughness than that of Ti-6Al-4V with equiaxed microstructure at a given strength, because the crack initiation of Ti-8Al-1Mo-1V were lower than that of Ti-6Al-4V. It is concluded that the relationship between microstructure and crack initiation or crack extension resistance properties of microcracks preceding unstable fracture accounted for the changes in fracture toughness of Ti-8Al-Mo-1V.
社団法人日本鉄鋼協会の論文
1990-04-01