The effect of laser beam operation mode on transition of grain morphology was studied during surface modification of alumina ceramic. A 4 kW HL 4006D continuous wave Nd:yttrium-aluminum-garnet (YAG) laser and a JK 701 pulsed Nd:YAG laser were employed to conduct surface modification of alumina. The laser beam operated in continuous wave mode generated faceted grain structure on the surface of the ceramic while the beam operated in pulsed mode produced nonfaceted grain structure. Such transition in grain morphology is mainly attributed to different levels of undercooling which is a function of cooling rates encountered in two different modes of laser operation.
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