Physical properties and formation mechanism of carbon nanotubes–ultrafine nanocrystals reinforced laser 3D print microlaminates

• LRP of Stellite SF12-CNTs/Stellite 12-CNTs-Cu laminate mixed powders can form the microlaminates.
• When laser power was not high enough, a portion of CNTs can be retained in bottom of LRP microlaminates.
• Cu was able to refine microstructure, favoring formations of UN (ultrafine nanocrystals).
• Surrounded amorphous promoted the formations of ultrafine nanoparticles.
• Twin crystals and high-angle grain boundary were obtained in such LRP microlaminates.

Rapid prototyping based on laser alloying by the pre-placed mixed powders has been used to produce the nanocrystals reinforced three-dimensional microlaminates in this study. Such microlaminates were fabricated on a TA7 titanium alloy by laser rapid prototyping (LRP) of the Stellite SF12-CNTs (carbon nanotubes)–Cu/Stellite SF12-CNTs laminate pre-placed powders. Through experimental work, it was confirmed that when laser power was not high enough, a portion of CNTs can be retained in bottom-layer of such LRP microlaminates; the Cu addition was able to refine the microstructures, also favoring the formations of ultrafine nanocrystals (UN). When laser power increased to a certain value, the boundary of such microlaminates became indistinguishable, and a great number of the coarse precipitates were also produced.