INFLUENCE OF CRYSTALLOGRAPHIC ORIENTATION ON TENSILE BEHAVIOR IN STRONGLY TEXTURED TI-6AL-4V

Differently shaped tensile test pieces cut from six orientations in a strongly textured 57 mm thick rolled and annealed Ti6Al4V bar have been tested, and the resulting properties and deformation behaviour have been related to crystallographic orientation. The expected deformation modes - {1010} 〈1120〉 slip and {1121} or {1012} twinning - were observed but, more importantly, direct evidence was also found for extensive 〈1123〉 slip, probably on {1122} planes; the apparently critical crystal orientation for this deformation mode is described. Considerable variations in deformation homogeneity were also observed and it was found that a parameter reflecting both the crystallographic behaviour and deformation homogeneity (the ratio of plane strain yield strength to uniaxial yield strength) showed an inverse hyperbolic-type relation with fracture toughness. The implications and possible use of this ratio are discussed. © 1979.