Properties are spatially varied in 3D printing parts due to the local microstructural inhomogeneity. Understanding the microstructural evolution is crucial for the production of quality 3D printing parts. To this end, a comprehensive clarification is presented on the microstructural heterogeneity of 3D printing parts fabricated from aluminium alloys and Inconel 625.

The additive layers of aluminium alloys (7475-T761, 5083-O, and 6061-T6) are fabricated by using the friction stir additive manufacturing technique, while Inconel additive layers are fabricated using the arc-direct energy deposition technique.

The low and high melting point reinforcement particles (Zn and Al₂O₃) are also added within the additive layers of the aluminium alloys to study the effect of reinforcement particles on the microstructural gradation.

The microstructural characterization was carried out using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and transmission electron microscopy techniques. The local mechanical properties were studied by using the miniature tensile specimens, hardness, and nano-indentation techniques.

Interestingly, it has been observed that the microstructural gradation is significantly high in the case of Al₂O₃ particles reinforced additive layers when compared with the Zn particles reinforced additive layers. On the contrary, the microstructural heterogeneity in the case of Inconel 625 additive layers is due to the re-melting and solidification of the previously deposited layers and repetitive heating and cooling thermal cycles.

It has been observed that the dendritic morphology of grain structure along with the detrimental intermetallic phases such as Laves phases and MC carbides are present. Understanding the physics related to these microstructural evolutions and their impact on property gradation are clarified in this work.

This article is shared by Md Murshid Imam, Kishor Kumar Jha and Rajnish Mishra.