Residual stress mapping in Inconel 625 fabricated through additive manufacturing: Method for neutron diffraction measurements to validate thermomechanical model predictions

作者：Wang Zhuqing; Denlinger Erik; Michaleris Panagiotis; Stoica Alexandru D; Ma Dong; Beese Allison M^*

来源：Materials and Design, 2017, 113: 169-177.

DOI：10.1016/j.matdes.2016.10.003

• Additive manufacturing
• Inconel 625
• Residual stress
• Neutron diffraction
• Thermomechanical modeling

The rapid solidification and subsequent thermal cycles that material is subjected to during additive manufacturing (AM) of a component result in a buildup of residual stresses, which lead to part distortion, and negatively impact the component's mechanical properties. We present a method for using neutron diffraction to validate thermomechanical models developed to predict the residual stresses in Inconel 625 walls fabricated by laserbased directed energy deposition. Residual stress calculations from neutron diffraction measurements depend strongly on the determination of stress-free lattice spacings. After measurement of stressed lattice spacings in Inconel 625 walls, reference samples were obtained by extracting thin slices from the walls and cutting combtype slits into these slices. Reference lattice spacings were measured in these slices, as well as equivalent slices that were also subjected to stress-relieving heat treatment. These heat treatments changed the reference lattice spacings, and therefore affected residual strain measurements. Further, this study shows the importance of using location-dependent reference lattice spacing, as during AM, the thermal history, and therefore elemental composition and stress-free lattice spacing, vary with position. Residual stresses measured by neutron diffraction along the build direction using comb-type reference samples without heat treatment were in good agreement with thermomechanical modeling predictions.

• 出版日期2017-1-5