The Effect of γ″ and δ Phase Precipitation on the Mechanical Properties of Inconel 718 Manufactured by Selective Laser Melting: An In Situ Neutron Diffraction and Acoustic Emission Study

Abstract

The deformation behavior of additively manufactured Alloy 718 in as-built condition and after annealing was studied in situ under tensile loading along the build direction. Pre-characterization by synchrotron X-ray diffraction and electron microscopy revealed a significant amount of γ″ precipitates in the as-built samples, whereas the γ″ phase was entirely consumed and needle-like δ precipitates appeared in the annealed sample. In situ neutron diffraction (ND) and acoustic emission (AE) enabled indirect observation of the role of the precipitates on the mechanical behavior. ND provided information on the load accommodation in the matrix, while AE detected a strong signal from the interaction of dislocations with the δ-phase precipitates during deformation of the annealed samples. The results imply that in the annealed samples the matrix sheds the load to the precipitates, while in the as-built material the matrix bares a significant load.

Diffraction-Based Residual Stress Characterization in Laser Additive Manufacturing of Metals

“…• DA: <200> texture along BD max. 3 m.r.d (corresponds to loading direction) [39] • 311 only slightly non-linear upon loading [39] • As built: 311 remains linear upon loading (<220> textured along BD) [186] • Heat-treated: 311 shows increased non-linearity (untextured) [186] • 311, 111 linear upon loading in as built condition, with increased non-linearity of (311) in heat-treated condition (possibly γ shedding load to δ) [187] • Low texture (max. 1.5 m.r.d) [143] • 311, 111 remain linear upon loading [143] • 220 displays non-linearity at larger strains [143] • 222 and 311 accumulate low intergranular strain [143] • Heat-treatments affect the micromechanical behavior upon loading • 311 appears suitable for as built samples • Texture up to 3 m.r.d has little influence on the choice of the lattice plane 316L (fcc)…”

Effect of ZrH2 particles on the microstructure and mechanical properties of IN718 manufactured by selective laser melting

“…6). Zr is known to promote the formation of carbides in conventional Ni-based superalloys [29][30][31] and it is assumed that ZrH2 particles were decomposed due to the high temperatures achieved during laser melting. The Zr was dissolved in the g Ni-matrix and the majority of Zr precipitated upon cooling, leading to a fine dispersion of small carbide particles within the cells (Fig.…”

“…These differences may be attributed to the evolution of the microstructure during deformation, namely deformation-induced precipitation of Nb in the form of carbides that can be promoted by Zr [29][30][31].…”

Bragg edge tomography characterization of additively manufactured 316L steel

“…Many applications of neutron characterization with diffraction [12][13][14][15][16][17][18] as well as white beam attenuation contrast neutron imaging [19,20] and neutron grating interferometry [21][22][23] can be found in the field of additive manufacturing (AM). These different techniques cover different aspects and complement each other, and can be integrated simultaneously as shown in [24] where the setup allows for an in situ combination of multimodal neutron imaging with neutron diffraction.…”