Quantifying microstructural contribution to yield stress and strain hardening of Ni20Cr alloy manufactured by laser powder bed fusion with different volumetric energy densities

• Published in: Journal of alloys and compounds 2023-12, Vol.968
• Main Authors: Joshi, Shubham Sanjay, Keller, Clément, Hug, Eric, Lefebvre, Williams
• Format: Article
• Language: English
• Subjects: Physics
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2023.172241

Laser powder bed fusion (LPBF) process is an additive manufacturing technique that focuses on intricate metalfabrication using laser processing of metallic powder. Various processing parameters like laser power, scanningspeed, and hatch spacing giving out unique applied volumetric energies are involved in such fabrication. Thosevaried energies bring about microstructural changes leading to modifications in mechanical response such asyield stress and strain hardening behaviour. In this work, we investigated the influence of volumetric energydensity on the aforementioned mechanical properties of a Ni-20 wt%Cr alloy manufactured via LPBF. First, ananalytical model was employed to study the contribution of each microstructural feature on yield stress of LPBFsamples. Dendritic cellular structures (and their sizes) are found to be the most important feature to govern thisparameter. The Kocks-Mecking model was further extended to associate the different strain hardening mecha-nisms with dislocation production and interaction mechanisms via different channels like dendritic cellularstructures, grains and forest dislocations. The production of dislocation via dendritic cellular structures is also themost significant mechanism for unique hardening behaviour in LPBF alloys. A modified equation of dislocationproduction mechanisms is finally proposed to simplify the application of this model for modelling the mechanicalbehaviour in tension of LPBF Ni20Cr.