| Popis: |
Mass loss due to vaporization induced by the high energy heat source during powder-bed fusion additive manufacturing (AM) is one of central issues which concerns the compositional variations across the AM build. Potentially, defects can be initiated where local chemistry in the AM build is not homogeneous. In this work, the evaporation effect of powder-bed fusion AM has been first developed in a binary alloy Nitinol (NiTi) and then applied to nickel-based superalloys via physics-based integrated modelling framework and experimental investigation. Volatile species which depart from the nominal composition result in significant mass lost up to 2 at% of Ni in the binary alloy system Nitinol, consistent with energy-dispersive X-ray analysis. As for the multicomponent alloy system of nickel-based superalloys, inductively coupled plasma optical emission spectroscopy (ICP-OES) results reveal further that Al, Co, and Cr are preferable to vaporize first with the loss up to 1.2 at%; this affects the thermal fluid behaviour given that the thermophysical property is altered by composition variations. Hierarchical microstructures have been characterized to rationalize the process-structure-property relationship. The mathematical tool validated with targeted experimentation can be further developed for AM materials design, particularly for taking care of vapourization. |
