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.