From the representative longitudinal and widthwise cross sections in Figures 5a and b,
the meltback can be observed to vary at the outer edges of the plate, with the trend being that as the scan progresses further into the plate the amount of meltback decreases. This phenomena is
attributed to the fact that melt pool is diffusing heat at a greater rate as it moves into the middle
of the plate; the increasing thermal mass causes the temperature of the melt pool to decrease at a
greater rate. It is this observation, which is evident throughout all the samples processed without
thermal control, that shows that precise thermal control will be required in order to achieve the
proper microstructure across a large deposit.