**5. Conclusions**

Novel high-throughput assays have been proposed and demonstrated to rapidly explore large material spaces reflecting the many combinatorial selections in material compositions and AM process parameters such as post-build aging treatments. More specifically, this study successfully conducted such an evaluation using Ti–Mn alloy systems processed by LENS, which allowed for the generation of samples with controlled composition gradients. Combining this strategy with spherical indentation stress–strain protocols allowed for a rapid exploration of the mechanical properties of the produced samples in small material volumes. Most importantly, this rapid exploration revealed that a Mn content of about 12% with a post-build heat treatment of 500 ◦C produced an unusually hard material with an expected tensile yield strength of 1864 MPa. The dataset generated in this study was analyzed rigorously using GPR models. The use of these statistical approaches revealed that the use of the Mn content and the post-build aging treatment as inputs does lead to reliable correlations with microstructure measures such as the β volume fraction and the averaged CLs of the α and β regions, as well as their mechanical properties such as the Young's modulus, indentation yield strength and indentation hardening rate. These correlations revealed the relative sensitivities of the different outputs to the selected inputs as well as the high levels of inherent noise in the estimation of the averaged CLs of β regions. The GPR models built with the limited data obtained in this work showed reasonable accuracy in leave-one-out cross-validation. This study established the feasibility and value of employing GPR approaches in the rigorous statistical analyses of the datasets produced in the proposed high-throughput assays for material exploration.

**Author Contributions:** Conceptualization, X.G., Y.C.Y., P.C.C. and S.R.K.; methodology, X.G., Y.C.Y., P.C.C. and S.R.K.; software, X.G. and Y.C.Y.; validation, X.G. and Y.C.Y.; formal analysis, X.G., Y.C.Y. and S.R.K.; investigation, X.G., Y.C.Y. and S.R.K.; resources, P.C.C. and S.R.K.; data curation, X.G. and Y.C.Y.; writing of the original draft preparation, X.G., Y.C.Y., P.C.C. and S.R.K.; writing of review and editing, X.G., Y.C.Y., P.C.C. and S.R.K.; visualization, X.G., Y.C.Y., P.C.C. and S.R.K.; supervision, P.C.C. and S.R.K.; project administration, P.C.C. and S.R.K.; funding acquisition, P.C.C. and S.R.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** X.G., P.C.C. and S.R.K. wish to acknowledge support provided by the National Science Foundation awards 1435237 and 1606567 ("DMREF/Collaborative Research: Collaboration to Accelerate the Discovery of New Alloys for Additive Manufacturing") with gratitude. Y.C.Y. gratefully acknowledges funding from N00014-18-1-2879. P.C.C. would also like to gratefully acknowledge the facilities at the University of North Texas, as well as Chandana Avasarala and Peyman Samimi for their contributions in the deposition of this Ti–xMn specimen.

**Conflicts of Interest:** The authors declare no conflict of interest.
