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In this study, the effect of laser source(CO 2 and Nd:YAG) on the microstructure and tensile properties of laser welded Al-Si coated boron steel(1.2mmt) was investigated with before and after hot-stamping. In case of as welds condition, fracture occurred in base metal unrelated to the laser source. It could be explained that tensile strength of fusion zone composed of martensite and bainite is higher than that of base metal that contains a lot of ferrite despite dilution of Al and Si from coating layer to fusion zone. In case of hot-stamping condition, the fracture occurred in fusion zone irrelevant to laser source and the tensile strength was lower than hot stamped base metal. In the CO 2 laser welds, Fe 3 (Al,Si) formed near the bond line was transformed into ferrite during hot-stamping. Therefore tensile strength of bond line is lower than that of base metal and center of fusion zone and the fracture occurred in the bond line. On the other hand, in the Nd:YAG laser welds, the higher concentration of Al formed the ferrite in the fusion zone during hot-stamping treatment. Also, the thickness of centerline was thinner than that of base metal. Therefore, it is considered that fracture occurred in centerline of fusion zone due to effect of concentration stress, and it leaded to a lower tensile strength and elongation.

In the current study, high performance liquid chromatography was used to validate and establish a method for identification of quisqualic acid (QA) in Quisqualis indica extract powder (HU033), which is widely used in health functional foods. Sample preparation was achieved by applying o-phthalaldehyde derivatization and protein hydrolysis. Analysis was performed on a C18 column with a gradient elution containing a mixture of sodium acetate (0.01 M, pH 4.6) and acetic acid (0.2 M) in water, and a flow rate of 1.0 mL/min methanol, detected at 338 nm. Method validation was achieved by measuring the specificity, linearity, accuracy and precision. Calibration curve of QA showed high linearity (R 2 =1), and limits of detection and quantification were determined to be 1.0 and 3.0 μg/mL, respectively. Recovery rate ranged from 98.66% to 101.11%, and QA content in HU033 was approximately 1.09%. Based on these results, we conclude that the developed method can be applied for quantifying QA in Quisqualis indica extract powder (HU033).

In this study, AISI M2 powder was selected primarily through various pieces of literature in order to improve the hardness and wear resistance. Among the laser metal deposition parameters, laser power was studied to improve the deposition efficiency in the laser metal deposition using a diode-pumped disk laser. An SKD61 hot work steel plate and AISI M2 powder were used as a substrate and powder for laser metal deposition, respectively. Experiments for the laser metal deposition were carried out by changing the laser power and track layer. The quality of the track surface and cross-section after applying the single-layer method was better than that obtained from applying the multi-layer method. As the laser power increased, the track thickness was increased, and the surface roughness deviation was decreased. In laser power condition of 1.6kW, the maximum hardness of the deposition track was 790Hv. This value was 40% better than the hardness of the SKD61 after heat treatment.

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