Lightweight steel is a crucial material that is being actively studied because of increased carbon emissions, tightening regulations regarding fuel efficiency, and the emergence of UAM, all of which have been recently labeled as global issues. Hence, new strategies concerning the thickness and size reduction of steel are required. In this study, we manufacture lightweight steel of the Fe-Mn-Al-C system, which has been recently studied using the DED process. By using 2.8 wt.% low-Mn lightweight steel, we attempt to solve the challenge of joining steel parts with a large amount of Mn. Among the various process variables, the laser scan power is set at 600 and 800W, and the laser scan speed is fixed at 16.67 mm/s before the experiments. Several pores and cracks are observed under both conditions, and negligibly small pores of approximately 0.5 μm are observed.

High-strength low-alloy (HSLA) steels show excellent toughness when trace amounts of transition elements are added. In steels, prior austenite grain size (PAGS), which is often determined by the number of added elements, is a critical factor in determining the mechanical properties of the material. In this study, we used two etching methods to measure and compare the PAGS of specimens with bainitic HSLA steels having different Nb contents These two methods were nital etching and picric acid etching. Both methods confirmed that the sample with high Nb content exhibited smaller PAGS than its low Nb counterpart because of Nb’s ability to hinder austenite recrystallization at high temperatures. Although both etching approaches are beneficial to PAGS estimation, the picric acid etching method has the advantage of enabling observation of the interface containing Nb precipitate. By contrast, the nital etching method has the advantage of a very short etching time (5 s) in determining the PAGS, with the picric acid etching method being considerably longer (5 h).

The effects of stevioside-containing sweetener (SCS) on kimchi quality were evaluated by investigating acid production, growth of lactic acid bacteria, sensory properties, and several volatile odor component (VOC)s of SCS-added kimchi. The concentrations of SCS added to kimchi instead of 1% white sugar were 0.165, 0.33, 0.66, and 1.32% (w/w). The pH of kimchi with higher amounts of added SCS generally increased, and the acidity of kimchi with higher amounts of added SCS generally decreased. Addition of higher amounts of SCS generally inhibited the growth of lactic acid bacteria in kimchi. Scores of overall acceptability for 0.33 or 0.66% SCS-added kimchi were significantly higher than those for other samples (p<0.05), whereas those for 1.32% SCS-added kimchi were significantly lower than those for other samples (p<0.05). The optimum concentration of SCS added to kimchi appears to be 0.33%. Among major VOCs identified in kimchi, the concentrations of seven components including ethanol generally decreased with addition of higher amounts of SCS, whereas that of diallyl disulfide was not changed markedly. The major VOCs contributing to desirable sensory properties of kimchi were likely dimethyl disulfide and diallyl sulfide.