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Wedge-shaped samples were manufactured by four different Additive Manufacturing (AM) processes, namely selective laser melting (SLM), electron beam melting (EBM), direct metal deposition (DMD), and wire and arc additive manufacturing (WAAM), using Ti-6Al-4V as the feed material. A high-resolution powder diffractometer was used to measure the diffraction patterns of the samples whilst rotated about two axes to collect detected neutrons from all possible lattice planes. The diffraction pattern of a LaB6 standard powder sample was also measured to characterize the instrumental broadening and peak shapes necessary for the Diffraction Line Profile Analysis. The line profile analysis was conducted using the extended Convolution Multiple Whole Profile (eCMWP) procedure. Once analyzed, it was found that there was significant variation in the dislocation densities between the SLMed and the EBMed samples, although having a similar manufacturing technique. While the samples fabricated via WAAM and the DMD processes showed almost similar dislocation densities, they were, however, different in comparison to the other two AM processes, as expected. The hexagonal (HCP) crystal structure of the predominant α-Ti phase allowed a breakdown of the percentage of the Burgers’ vectors possible for this crystal structure. All four techniques exhibited different combinations of the three possible Burgers’ vectors, and these differences were attributed to the variation in the cooling rates experienced by the parts fabricated using these AM processes.

The evolution of dislocation density and microstructure of a hot rolled Zr–2.5Nb alloy under compressive plastic strain, at room temperature, was analysed using neutron diffraction and transmission electron microscopy (TEM). The dislocation densities of type 〈a〉, 〈c + a〉 and 〈c〉 dislocations at different plastic strains in the elastic–plastic transition regime and plastic regime have been measured by diffraction line profile analysis (DLPA). TEM microstructure characterization revealed the operation of different slip systems. It has been found that slip of type 〈a〉 dislocations contributed to most of the plastic strain at the early stage of deformation, and strong pyramidal 〈c + a〉 slip did not occur until the deformation was fully plastic. Unambiguous evidence of basal slip occurring at room temperature in Zr is provided. Loading along a plate direction with more basal poles favoured the operation of basal and pyramidal slip. Dislocation features including relative edge:screw character of 〈c + a〉 dislocations are shown to be different under tension and compression loading, providing a mechanistic driver for the previously observed asymmetry in critical resolved shear stress for 〈c + a〉 slip. [ABSTRACT FROM PUBLISHER]

Wedge-shaped samples were manufactured by four different Additive Manufacturing (AM) processes, namely selective laser melting (SLM), electron beam melting (EBM), direct metal deposition (DMD), and wire and arc additive manufacturing (WAAM), using Ti-6Al-4V as the feed material. A high-resolution powder diffractometer was used to measure the diffraction patterns of the samples whilst rotated about two axes to collect detected neutrons from all possible lattice planes. The diffraction pattern of a LaB6 standard powder sample was also measured to characterize the instrumental broadening and peak shapes necessary for the Diffraction Line Profile Analysis. The line profile analysis was conducted using the extended Convolution Multiple Whole Profile (eCMWP) procedure. Once analyzed, it was found that there was significant variation in the dislocation densities between the SLMed and the EBMed samples, although having a similar manufacturing technique. While the samples fabricated via WAAM and the DMD processes showed almost similar dislocation densities, they were, however, different in comparison to the other two AM processes, as expected. The hexagonal (HCP) crystal structure of the predominant α-Ti phase allowed a breakdown of the percentage of the Burgers' vectors possible for this crystal structure. All four techniques exhibited different combinations of the three possible Burgers' vectors, and these differences were attributed to the variation in the cooling rates experienced by the parts fabricated using these AM processes. [ABSTRACT FROM AUTHOR]