Microstructural control in a Ti-based alloy by changing laser processing mode and power during direct laser deposition

• Continuous wave plus pulsed wave laser mode promotes formation of equiaxed grains.
• Increased laser power leads to coarser microstructure.
• Laser power shows more influence than laser mode on the size of grains and phases.

Ti-6Al-4V samples have been fabricated by direct laser deposition using different laser powers and two different laser processing modes, continuous wave (CW) mode and CW+PW (pulsed wave) mode. The as-fabricated microstructure was investigated using photography, optical microscopy and secondary electron microscopy. It was found that both laser mode and laser power show significant influence on grain structure. The CW mode generally leads to well-developed large columnar grains whereas the CW+PW mode tends to give rise to much finer equiaxed grains. Higher laser power was found to result in larger grains and coarser microstructure.