The detailed laser surface remelting experiments of Cu-31.4 wt pct Mn and Cu-26.6 wt pct Mn alloys on a 5 kW CO2laser were carried out to study the effects of processing parameters (scanning velocity, output power of laser) on the growthdirection of microstructure in the molten pool and cellular spacing selection under the condition of ultra-high temperaturegradient and rapid directional solidification. The experimental results show that the growth direction of microstructure isstrongly affected by laser processing parameters. The ultra-high temperature gradient directional solidification can be realizedon the surface of samples during laser surface remelting by controlling laser processing parameters, the temperature gradientand growth velocity can reach 106 K/m and 24.1 mm/s, respectively, and the solidification microstructure in the center ofthe molten pool grows along the laser beam scanning direction. There exists a distribution range of cellular spacings underthe laser rapid solidification conditions, and the average spacing decreases with increasing of growth rate. The maximum,λ minimum, λmin, and average primary spacing,λ, as functions of growth rate, Vb, can be given by, λ =12.54V b-0.61,λmin=4.47 Vb-0.52, λ=9.09Vb-0.62, respectively. The experimental results are compared with the current Hunt-Lu model forrapid cellular/dendritic growth, and a good agreement is found.
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