Abstract:The anisotropy of tensile properties and fracture toughness of Ti-6Al-4V (Ti64) alloy fabricated by β forging was investigated. In order to evaluate anisotropic mechanical properties, the microstructure and crystallographic texture of billets with different orientations were characterized, and the influence of sampling direction on tensile properties and fracture toughness was studied. The results reveal that the prior β grains of Ti64 billet display pan-cake-type characteristics. At room temperature, the alloy is mainly composed of α phase, and several α phase variants produced by β→α phase transformation decrease the α texture intensity. The anisotropy of mechanical properties is affected by prior β grain morphology and the slip activation related to α texture. The initiation toughness was obtained by the J-integral resistance curve method. The initiation toughness was divided into intrinsic and extrinsic toughness by calculation. The anisotropy of intrinsic toughness is mainly attributed to the size of crack tip plastic zone, which is affected by prior β grain morphology. In contrast, the extrinsic toughness is affected by zigzag degree of crack, which is mainly influenced by α lamellae and colonies.

Key words: titanium alloy; β forging; texture; J-integral; fracture mechanism; anisotropy