The Role of Ti and B Additions in Grain Refinement of Al–Mn Alloy During Laser Additive Manufacturing

In the present work, we investigated the governing mechanism of grain refinementGrain refinement in AA3104 Al–Mn alloyAl-Mn alloys made by laserLaser direct energy deposition (DED) additive manufacturingAdditive manufacturing (AM). The microstructureMicrostructure development and phase transformationPhase transformation of DED AM AA3104 were studied by adding different concentrations of Ti, B, Ti–B mixture, and TiB2 particles as grain refinersGrain refiner. The transition from large columnar grains to fine equiaxed grains was achieved by Ti or Ti–B addition, but not by B or TiB2 addition. The study demonstrated that reactive additive manufacturingAdditive manufacturing may be a more effective way to refine grains than directly adding ceramic particles. The formation of Al3Ti plays the most critical role in grain nucleation during DED AM.