The solidification morphology analysis of fine Cu powder melted by a raster
scanned energy beam from a focused Nd:YAG laser is presented here. The powder was
processed inside of sealed chamber where it was subjected to a high vacuum cycle. The
laser fusion process consisted raster scanning a narrow rectangular pattern with a high
density of scanning lines, the chamber was purged with inert gas during the process. Up
to a 3.3 mm/s laser travel speed and maximum laser power level of 240 W were used to
melt a 2 mm thick bed of loose powder. The resulting solidified ingots were separated
into categories based on their shape integrity. Metallographic analysis by means of
optical microscopy and scanning electron microscopy was performed on the cross section
and longitudinal section of the ingots with homogeneous surface and complete shape
integrity. Characterization revealed an elongated columnar grain structure with a grain
orientation along the direction of the laser travel direction, some degree of porosity was
observed too in some of the specimens. It was observed that grains diameter ranged from
10 to 100 µm and contained a two phase eutectic microstructure of copper and it oxides.
Oxygen content was accounted from a 5.5 up to 8.1 atomic percent, a small percentage of
chlorine was present, too. A 2 to 8 percent variation in the Vickers microhardness values
were found between the different specimens when measured along the longitudinal
section. These HV values corresponded to approximate 20-25% cold rolled oxygen free
copper (80-90 HV). The ingots thus produced suggest that a multilayer structure from Cu
powder could be build by the SLM process having sufficiently adequate compositional,
microstructure and mechanical properties for functional applications.Mechanical Engineerin
