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Abstract

The paper presents the study results of laser modification of Vanadis-6 steel after diffusion boronized. The influence of laser beam fluence on selected properties was investigated. Diffusion boronizing lead to formation the FeB and Fe2B iron borides. After laser modification the layers were consisted of: remelted zone, heat affected zone and substrate. It was found that increase of laser beam fluence have influence on increase in dimensions of laser tracks. In the thicker remelting zone, the primary dendrites and boron eutectics were detected. In the thinner remelting zone the primary carbo-borides and eutectics were observed. In obtained layers the FeB, Fe2B, Fe3B0.7C0.3 and Cr2B phases were detected. Laser remelting process caused obtained the mild microhardness gradient from the surface to the substrate. In the remelted zone was in the range from 1800 HV0.1 to 1000 HV0.1. It was found that the laser beam fluence equal to 12.7 J/mm2 was most favorable. Using this value, microhardness was relatively high and homogeneous.
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Abstract

Micro-channel heat sinks are used in a wide variety of applications, including microelectronic devices, computers and high-energy-laser mirrors. Due to the high power density that is encountered in these devices (the density of delivered electrical power up to a few kW/cm2) they require efficient cooling as their temperatures must generally not exceed 100 ◦C. In the paper a new design for micro-channel heat sink (MCHS) to be used for cooling laser diode arrays (LDA) is considered. It is made from copper and consisting of 37 micro-channels with length of 9.78 mm, width of 190 μm and depth of 180 μm with the deionized water as a cooling medium. Mathematical and numerical models of the proposed design of the heat sink were developed. A series of thermofluid numerical simulations were performed for various volumetric flow rates of the cooling medium, its inlet temperature and different thermal power released in the laser diode. The results show that the LDA temperature could be decreased from 14 to 17% in comparison with earlier proposed design of the heat sink with the further drop in temperature obtained by applying indium instead of gallium arsenide as the soldering material between the LDA and MCHS interface. Moreover, it was found that the maximum temperature, and therefore the thermal resistance of the considered heat sink, could be decreased by increasing the coolant flow rate.
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