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采用激光立体成形(LSF)技术制备了Ti-6Al-4V平面应变断裂韧度(KIC)试样。沿沉积高度方向,沉积态组织呈现典型的β晶粒外延生长特性,β晶粒的平均宽度约为100~400μm,长度可达若干厘米,β晶粒内由细密的针状α及α+β板条组成。Ti-6Al-4V激光立体成形沉积态试样的KIC≥52.6 MPa.m1/2,达到锻件标准要求,不过,由于沉积态的组织特征,KIC具有典型的各向异性,与拉伸性能所表现的各向异性一致。β晶内细密α+β编织的魏氏组织的抗裂纹扩展能力较强,使得裂纹扩展对β晶界非常敏感。当裂纹扩展面垂直于β晶界时,KIC最高;在裂纹沿β晶界扩展的情况下,单位面积内的晶界长度越长越曲折,则KIC越高。裂纹扩展方向与β晶界的夹角(0~90°)越大,β晶粒越细小,裂纹扩展越困难。
Ti-6Al-4V plane strain fracture toughness (KIC) samples were prepared by laser solid state forming (LSF) technique. Along the depositional height, the deposited microstructure presents the typical β-grain growth characteristics. The average grain size of β grains is about 100-400μm and the length is up to a few centimeters. The fine grains of a-grains are composed of fine acicular α and α + β Lath composition. The KIC of the as-deposited Ti-6Al-4V laser is more than or equal to 52.6 MPa.m1 / 2, which meets the standard requirements of the forgings. However, due to the characteristics of the as-deposited structure, the KIC exhibits typical anisotropy and tensile properties The anisotropy is consistent. The β-crystal fine α + β braided Wistar structure is more resistant to crack propagation, so that the crack propagation is very sensitive to the β grain boundary. When the crack propagation plane is perpendicular to the β grain boundary, KIC is the highest. In the case of crack propagation along the β grain boundary, the longer the grain boundary length per unit area, the more tortuous the grain boundary, the higher the KIC. The larger the included angle (0 ~ 90 °) between crack growth direction and β grain boundaries, the finer the β grains and the more difficult the crack growth.