Friction stir processing (FSP) is a technique for altering the microstructure of a material via concentrated plastic deformation and typically leads to improved mechanical, fatigue, and wear performance. The deformation is created by forcibly inserting a non-consumable tool into the workpiece and rotating it while pushing it laterally. To enhance performance attributes such as hardness, and yield strength, the relationship between process parameters and microstructural features are being researched. Numerous process variables are known to influence the microstructure and properties of the FSP material; however, the exact relationships between process variables, and microstructure and performance properties have yet to be completely studied. Using response surface approaches, we create explainable polynomial models for describing process-microstructure-property relationships in this effort that are corroborated as necessary by high fidelity physics models. In addition, parametric and non-parametric techniques are employed to quantify uncertainty, and subsequent experiments are designed using quasi-Monte Carlo Spacefilling techniques.