[en] Evolution of abnormally growing Goss grains in Fe–3%Si steel was observed time sequentially by electron backscattering diffraction (EBSD). For example, some specimens were heated at 1080 °C for 5 min, then cooled, polished and observed by EBSD, whose procedure was repeated for 6 times. After each heat treatment at 1080 °C, the abnormal grain growth morphology of Goss grains in Fe–3%Si steel could be observed by polishing away a thin layer of the oxidized surface. Goss grains grew abnormally in a highly irregular way. As a result, some matrix grains were isolated at the growth front, which produced island grains. The irregular growth often resulted in incomplete isolation, which produced peninsular grains. Numerous matrix grains were isolated by the impingement of abnormally growing Goss grains. Once matrix grains became isolated, island or peninsular grains, they shrank much faster than before. If the grain boundary mobility of island and peninsular grains is not low enough, they would shrink in an accelerated way because their local curvature of grain boundary becomes larger as they shrink. Therefore, the high shrinking rate of island and peninsular grains indicates that island and peninsular grains are formed not because of their low grain boundary mobility but because of solid-state wetting.

[en] Highlights: • The range of SLM process condition to achieve over 99.5% relative planar density of SUS316L. • Correlation study between microstructural, mechanical and chemical properties of SUS316L according to the high density process conditions for SLM. • Locally property tuning of SUS316L part by controlling the process condition of SLM selectively. The effects of laser energy density on microstructural, mechanical properties, and chemical composition of stainless steel 316 L (SUS316L) parts fabricated by selective laser melting (SLM) technology were studied. Total 36 specimens were fabricated under the range from 1.3 to 46.7 J/mm³. The process conditions to achieve over 99.5% ± 0.1% relative planar density were obtained, and the mechanism of tunable mechanical properties was investigated by understanding the correlation between the microstructure and chemical composition according to the energy density. As the energy density increased, tensile properties were decreased with grain growth and the concentrations of light elements were increased by accelerating dissolution. As the concentrations of light elements increased, the mechanism of destructive behavior changed from ductile fracture to brittle fracture and it caused that the hardness was improved. Consequently, it was necessary to control the energy density from 9.34 to 23.98 J/mm³ in order to fabricate SUS316L parts of high strength and high elongation characteristics by SLM method.

[en] Highlights: • Corrosion properties of friction welded dissimilar aluminum alloys seem to be governed by the anode part in the weld. • Intense corrosion near the interface has the limited region due to insufficient ionic transport. • Self-formation of a micro-galvanic cell is a main reason for the inferior corrosion performance. - Abstract: Corrosion behaviors of the friction welded dissimilar aluminum alloys were investigated to understand how galvanic effect plays a role in altering corrosion properties of the dissimilar weld. From the fact that the weld had the similar OCP value to that of AA2017, it can be inferred that the corrosion characteristics of the weld is under the control of the AA2017 part in the weld and as a result, only the AA2017 part in the weld had experienced severe corrosion, leaving AA6063 under cathodic protection. Intense corrosion occurring near the interface implies that the area near the interface is placed under the effect of galvanic corrosion and there was the effective distance where the galvanic effect exerts an impact due to the increase in the resistance of the electrolyte with the distance from the interface. The disappearance of Warburg diffusion plot in Nyquist plots for the weld seemed to be the breakdown of the passivation layer related to the formation of the micro-galvanic cell, which in turn presented the shrinkage in the capacitance response, indicating that charge reactions in the form of corrosion occurred.