# Design and Assessment of an Austenitic Stainless Alloy for Laser Powder Bed Additive Manufacturing
## 4 Conclusions  
In this study, a genetic algorithm was used to optimize a single-phased, iron-rich austenitic alloy for additive manufacturing. The Hull diagram provided feasibility constraints and the Scheil model addressed solidification conditions. The Labusch model was used to evaluate and to increase solid solution strengthening, to promote improved mechanical resistance. Minimizing the coefficient of thermal expansion (\(\alpha_{\text{CTE}}\)), vaporization fluxes and reducing surface tension were key objectives to reduce porosity or distortions. The risk of cracking was also minimized via several criteria. These objectives and constraints were integrated into a multi-objective genetic algorithm, resulting in the identification and selection of a new optimized composition with improved printability. The optimized alloy powder was produced by gas atomization and then used in the LPBF process to produce specimens for microstructural and mechanical characterization.  
The study leads to the following conclusions:  
* The overall optimization method efficiently converges on a promising set of optimized alloys with expected attractive properties as predicted by the models.
* The selection of a single alloy proves to be challenging and requires the introduction of an additional criterion regarding the stability range of austenite to aid in the decision-making process.
* The selected alloy produced crack-free parts with a low porosity rate, even when printed using standard processing parameters. This confirms the effectiveness of the design process in eliminating critical defects and ensuring high ductility.
* The LPBF material consists of a single FCC phase. As predicted, its coefficient of thermal expansion is slightly higher than that of 316L stainless steel. Tensile tests showed good ductility, with strength values comparable to other LPBF-printed austenitic steels such as 316L. These experimental results confirm the accuracy of the CALPHAD model and other analytical models, and increase confidence in the alloy property predictions made during the optimization stage.
* The overall performance of the alloy was found to be quite comparable to 316L. Expansion coefficient measurements showed only a 3% difference from 316L. Mechanical properties were also comparable, with similar levels of hardness and elongation. However, the yield strength and UTS of the optimized alloy were 17% lower. Therefore, further improvements should be considered in the optimization process to surpass existing austenitic alloys such as 316L.  
Future steps could consider additional criteria such as material cost, density, and spatter formation. New criteria could also focus on reducing sensibility of the powder to oxidation; however, these criteria relate more to the powder itself than to the alloy composition alone, making it difficult to address from an alloy-only perspective. While the study demonstrates feasibility, targeting specific applications has promising industrial potential.  
Conceptualization, F.T., A.F. and J.F.; methodology, M.A., J.F., F.T. and A.F.; formal analysis, M.A., J.F., A.F. and F.T.; investigation, M.A. and M.B.; resources, A.F. and F.T.; writing--original draft preparation, M.A. and J.F.; writing--review and editing, J.F., F.T. and A.F.; supervision, J.F., F.T. and A.F.; funding acquisition: J.F. and A.F. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
All the authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.