Physical properties and microstructures of nanocrystals reinforced ice laser 3D print layer

• Ice addition decreases maximum temperature of molten pool during the LRP process.
• Ice addition promoted the formations of nanocrystals in LRP layer.
• Growth of nanocrystals was retarded by surrounded amorphous in a certain extent.
• Surrounded amorphous promoted the formations of ultrafine nanoparticles.
• Twin crystals and the high-angle grain boundary were obtained in such LRP layer.

Rapid prototyping based on laser alloying by the pre-placed mixed powders has been used to produce the nanocrystals reinforced three-dimensional layer in this study. Such a layer was fabricated on a TC17 titanium alloy by laser rapid prototyping (LRP) of the Co–Sb–TiB2 mixed powders in ice. Scanning electron microscope (SEM) and high resolution transmission electron microscopy (HRTEM) test results indicated that the ice addition was able to decrease the maximum temperature of molten pool during the LRP process, favoring the formation of nanocrystals; growth of such nanocrystals was retarded by the surrounded amorphous in a certain extent, favoring the formations of ultrafine nanoparticles (UN), and the twin crystals and the high-angle grain boundaries were also observed; differential thermal analysis (DTA) test was used to explain the physical properties and formation mechanism of amorphous–nanocrystals, and also the relationship between the amorphous and nanocrystalline phases in such a LRP layer.

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