In Situ Electron Backscatter Diffraction Study of Deformation Inhomogeneity under Uniaxial Tension of Laser Melting Deposited TA15 Alloy

The discourse of the anisotropic mechanical properties of a unit-built additively manufactured component depends on its microstructural features and inhomogeneous distribution. This work explores the microstructure distribution and deformation inhomogeneity during uniaxial tension of a laser melting deposited TA15 near-alpha titanium alloy via advanced in situ secondary electron microscopy and electron backscattered diffraction characterization. Microscopically, two major regions can be distinguished in the overall microstructure, including a Widmanst & auml;tten (alpha w) region along the prior beta-grain boundary (GB) and a basketweave-alpha region within the columnar grains. These two different microstructural regions responded differently under the same tensile load conditions. In the early deformation stage, only conventional slip occurred in the basketweave-alpha region, whereas microscale shear bandings developed in both the basketweave-alpha and alpha w regions. As the deformation progressed, the strain was optimally accommodated by the basketweave-alpha region. Nevertheless, the largest strain accumulation occurred along the prior beta-GB because of a high misorientation angle, which resulted in the formation of cracks. Subsequently, the growth and propagation of the cracks along the prior beta-GB were relatively fast due to the weak obstruction caused by the low angle of misorientation in the alpha w region, resulting in early fracture of the sample.