METAL ADDITIVE MANUFACTURING (AM) OFFERS NEW OPPORTUNITIES TO ENHANCE COMPONENT PERFORMANCE BY CUSTOMIZING PARTS FOR THEIR RELEVANT USE CASES. WITH LAYER-BY-LAYER PRINTING OF COMPLEX PARTS, AM CAN CREATE FUNCTIONALLY GRADED MATERIALS (FGMS) THAT CONTINUOUSLY TRANSFORM FROM ONE ELEMENT TO ANOTHER – GENERATING REGIONALLY-VARIED PROPERTIES FIT TO THE FUNCTIONAL REQUIREMENTS. DESPITE ITS IMMENSE OPPORTUNITY, METAL AM’S IMPLEMENTATION IS LIMITED BY THE SIGNIFICANT PERFORMANCE VARIABILITY DUE TO THE RAPIDLY EVOLVING HARSH ENVIRONMENTS THAT TRANSFORM AND DEGRADE MATERIALS IN WAYS THAT WE STRUGGLE TO CONTROL. FUNDAMENTAL STUDIES REVEAL COMPLEX MULTI-PHYSICS TRENDS THAT ARE DIFFICULT TO RECONCILE, BUT FOR THE FULL VERSATILITY OF LPBF TO BE EXPLOITED, WE REQUIRE NEW OPERANDO X-RAY DIAGNOSTICS. THIS SSAA PROJECT IS DEVELOPING A NEW CLASS OF OPERANDO MULTISCALE X-RAY MICROSCOPES TO DIRECTLY MAP CRITICAL SCIENCE REQUIRED FOR RELIABLE METAL-AM – FOCUSING ON LASER POWDER BED FUSION (LPBF). THE PREVIOUS SSAA AWARD DEVELOPED THE FIRST NANOSCALE OPERANDO IMAGING OF LPBF AND DIRECTLY REVEALED DEFECT FORMATION MECHANISMS NOT PREVIOUSLY UNDERSTOOD. THE OBJECTIVE OF THE PRESENT PROPOSAL IS TO USE AND DEVELOP THE NOVEL MICROSCOPES TO STUDY THE ALLOY MIXING BEHAVIORS OF IN-SITU ALLOYING REQUIRED FOR FGMS. THE NOVEL NANO- AND MICROSCALE MICROSCOPES WILL QUANTIFY THE INITIAL DRIVING FORCES FOR AL-CU MIXING DYNAMICS ORIGINATING FROM A MIXTURE OF PURE ELEMENTAL POWDERS. THEY WILL THEN DIRECTLY MEASURE THE 3D FLOW DYNAMICS IN-SITU FOR THE FIRST TIME BY DEVELOPING THE OPERANDO LIMITED VIEW TOMOGRAPHY (LVT) OF LPBF. BY ESTABLISHING A SUITE OF TIME-RESOLVED 2D AND 3D X-RAY MICROSCOPES WITH ANALYSIS METHODS TO TRACK STATISTICAL DYNAMICS, THE NEW EXPERIMENTAL “TOOLBOX” WILL CONNECT THE COMPLEX MULTI-PHASE DYNAMICS NATIVE TO THE EXTREME CONDITIONS OF LPBF TO SOLVE OPEN CHALLENGES FOR FGMS.