Precision castings requiring a fine finish and having complex internal geometries can be produced by casting a semi-solid thixotropic metal alloy within or about a melt-away metal component in the form of a core and/or a die insert that has a lower melting point than the solid-to-semi-solid transition temperature of the thixotropic alloy The thixotropic alloy may be cast, e.g., by thixocasting, rheocasting, sub liquidus casting. Then, after the alloy solidifies to form a casting with a captured melt-away component, the component is melted from the casting, preferably using a liquid bath. Process robustness, speed, and versatility can be enhanced by coating the component with a thin, uniform, abrasion-resistant, and thermally resistant coating that prevents excessive heat from being transferred to the component from the alloy and that prevents the component from alloying with the casting.