Kobe Steel

About: Kobe Steel is a company organization based out in Kobe, Japan. It is known for research contribution in the topics: Alloy & Welding. The organization has 5467 authors who have published 5710 publications receiving 58056 citations. The organization is also known as: Kobe Steel, Ltd. & Kabushiki-gaisha Kōbe Seikō-sho.

Yield function development for aluminum alloy sheets

Abstract: In this work, yield surfaces were measured for binary aluminum-magnesium sheet samples which were fabricated by different processing paths to obtain different microstructures. The yielding behavior was measured using biaxial compression tests on cubic specimens made from laminated sheet samples. The yield surfaces were also predicted from a polycrystal model using crystallographic texture data as input and from a phenomenological yield function usually suitable for polycrystalline materials. The experimental yield surfaces were found to be in good agreement with the polycrystal predictions for all materials and with the phenomenological predictions for most materials. However, for samples processed with high cold rolling reduction prior to solution heat treatment, a significant difference was observed between the phenomenological and the experimental yield surfaces in the pure shear region. In this paper, a generalized phenomenological yield description is proposed to account for the behavior of the solute strengthened aluminum alloy sheets studied in this work. It is subsequently shown that this yield function is suitable for the description of the plastic behavior of any aluminum alloy sheet.

Synthesis of diamonds by use of microwave plasma chemical-vapor deposition: Morphology and growth of diamond films

Abstract: An investigation is made of the surface morphology and growth of polycrystalline diamond films deposited on Si substrates using the microwave plasma chemical-vapor-deposition (CVD) method. For the source gas, ${\mathrm{CH}}_{4}$ and ${\mathrm{H}}_{2}$ gases mixed in different concentrations are used. Scanning electron microscope pictures of the diamond films synthesized for 7 h show that the film surface consists of triangular (111) diamond faces for ${\mathrm{CH}}_{4}$ concentrations c0.4 vol %, whereas square (100) faces are predominant above c\ensuremath{\simeq}0.4 vol %. For c\ensuremath{\gtrsim}1.2 vol %, the number density of (100) faces decreases with c and finally at c\ensuremath{\simeq}1.6 vol % the film surface becomes entirely structureless, consisting of microcrystallites only. For characterization of the films, x-ray and electron diffraction are measured along with Raman and infrared spectra. In the study of the evolution of surface morphology during film growth, it is found that diamond particles grown on the substrate initially increase their size almost uniformly until the substrate is entirely covered. Then a secondary growth takes place, followed by surface-restructuring processes such as ``fusion'' and ``absorption'' among secondary crystallites. As a result, well-defined diamond faces are formed progressively on the film surface. Higher-order growths followed by the restructuring processes occur periodically as the CVD synthesis proceeds.

Effects of Volume Fraction and Stability of Retained Austenite on Ductility of TRIP-aided Dual-phase Steels

Abstract: The effects of silicon and manganese contents on volume fraction and stability of retained austenite particles in 0.2C-(1.0-2.5)Si-(1.0-2.5)Mn (mass%) TRIP-aided dual-phase steels were investigated. In addition, the relationships between above retained austenite parameters and ductility at room and moderate temperatures were discussed through studies on strain-induced transformation behavior of retained austenite.As increasing the silicon and manganese contents except for 2.5 mass% manganese steel, the initial volume fraction of retained austenite increased with accompanied by reducing carbon concentration in retained austenite. It was found that the ductilities of these steels became maximum at a given temperature between 23 and 175°C, i.e., a peak temperature. The peak temperature was concluded to agree well with the temperature at which the strain-induced transformation of retained austenite was suppressed moderately for each steel. Moreover, the peak temperature Tp (°C) was related to estimated martensite-start temperature Ms (°C) of the retained austenite as Tp=3.04Ms+187. Strength-ductility balance, i.e., the product of tensile strength and total elongation, at the peak temperature linearly increased with an increase in the initial volume fraction of retained austenite.

Ductility and strain-induced transformation in a high-strength transformation-induced plasticity-aided dual-phase steel

Abstract: The influence of forming temperature and strain rate on the ductility and strain-induced transformation behavior of retained austenite in a ferritic 0.4C-1.5Si-1.5Mn (wt pct) dual-phase steel containing fine retained austenite islands of about 15 vol pct has been investigated. Ex- cellent combinations of total elongations (TELs), about 48 pct, and tensile strength (TS), about 1000 MPa, were obtained at temperatures between 100 °C and 200 °C and at a strain rate of 2.8 X 10-4/s. Under these optimum forming conditions, the flow curves were characterized by intensive serrations and increased strain-hardening rate over a large strain range. The retained austenite islands were mechanically the most stable at temperatures between 100 °C and 200 °C, and the retained austenite stability appeared to be mainly controlled by strain-induced martensite and bainite transformations (SIMT and SIBT, respectively), with deformation twinning occur- ring in the retained austenite. The enhanced TEL and forming temperature dependence of TEL were primarily connected with both the strain-induced transformation behavior and retained aus- tenite stability.