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In this study, finite element (FE) simulation by the software Abaqus was relied on to investigate the roll forming process of a wheel rim made of an innovative dual-phase steel, i.e., DP590, after flash butt welding (FBW). In the simulation, an FE model was generated, including the design of the dies for flaring, three-roll forming, and expansion, and detailed key processing parameters based on practical production of the selected DP590. Combined with the microstructures and properties of the weld zone (WZ) and heat-affected zones (HAZs) after FBW, the distribution of stress/strain and the change in thickness of the base metal (BM), WZ and HAZs were analyzed, and compared in the important stages of roll forming. Theoretically, the variation in the microstructure and the corresponding stress–strain behaviors of the BM, WZ, and HAZs after FBW have led to the thickness reduction of DP590 that originated from softening behaviors occurring at the region of subcritical HAZs (SCHAZs), and a small amount of tempered martensite has evidently reduced the hardness and strength of the SCHAZ. Meanwhile, the distribution of stress/strain has been influenced to some extent. Further, the study includes the influence of the friction coefficient on the forming quality of the wheel rim to guarantee the simulation accuracy in practical applications. In sum, the dual-phase steel has to be carefully applied to the wheel rim, which needs to experience the processes of FBW and roll forming, focusing on the performance of SCHAZs. [ABSTRACT FROM AUTHOR]

The AZ91D magnesium alloy samples were scanned by millisecond pulse Nd:YAG laser under high pure argon protection. The surface morphology, microstructure and composition of the treated magnesium alloy were studied by X-ray diffraction, optical microscopy, scanning electron microscopy, atomic force microscopy. In addition, the corrosion surface which was corroded using simulated body fluid and the mass fraction of 3.5%NaCl solution was observed and material corrosion rate was calculated. The results show that, at the same corrosion time, compared with the untreated samples, the surface corrosion resistance is improved by the enrichment of Al at the irradiated surface by the joint effect of the combination of refined homogeneous microstructure of α-Mg phase and β-Mg17Al12 phase and the selective vaporization and the chemical composition of base metal in the laser-treated AZ91D alloy; the solidification equation is obtained by calculating the relation between the size of the dendrite cell and the cooling rate in laser melting zone.

In this work, the effects of the preparation conditions on the electro-optical performance and the polymer morphology of the polymer dispersed liquid crystal (PDLC) samples in which the polymer matrix contained polyhedral oligomeric silsesquioxane (POSS) microstructure were studied. The results confirmed the dramatic improvement effect of POSS microstructure for the electro-optical properties of PDLC. Moreover, the electro-optical performance and the polymer morphology of the PDLC samples with POSS microstructure can be regulated successfully by the preparation conditions, such as UV light intensity and polymerization temperatures. This work can provide a way for regulating methods for PDLC films. [ABSTRACT FROM AUTHOR]

Silver polymer electrolyte membranes containing inorganic nanoparticles have showed excellent facilitated olefin transport properties. However, the application of facilitated transport membranes has been significantly hampered because of the poor stability of silver ions carrier. The structural changes of the facilitated transport membranes corresponding to the reduced separation performance with an extended time have rarely been studied. In this study, titanium dioxide (TiO 2 ) nanoparticles were introduced into poly(ethylene oxide) (PEO)/silver tetrafluoroborate polymer electrolyte membranes for propylene/propane separation. X-ray diffraction (XRD) analysis indicated that the addition of TiO 2 and silver salt reduced the crystallinity of PEO. The selectivity of propylene/propane of the polymer electrolyte membrane increased with increasing concentration of silver salt and TiO 2 in the polymer matrix. However, the propylene/propane selectivity decreased from 19.04 to 5.40 as the silver carrier ions became deactivated over the course of 196 h experiment. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that the satellite TiO 2 nanoparticles were formed around the silver salt after the composite membrane was placed in the air for 10 d. The findings in this work highlight the understanding of the carrier stability in polymer electrolyte membranes, and provide a potential opportunity to develop more stable polymer/carrier systems for the application of facilitated olefin transport membranes. [ABSTRACT FROM AUTHOR]

( K,Na) NbO3 ( KNN) lead-free ceramics were fabricated using conventional solid-state reaction method. The domain configurations were studied with transmission electron microscopy and found to be closely related to the sintering temperature and cooling rate. High density ceramics with uniform compositions were obtained when sintered at 1200°C with a slow cooling rate, resulting in the improved piezoelectric properties, with d33 on the order of 150-160 pC/N, which is comparable to the hot pressed KNN ceramics. The microstructures of the ceramics synthesized at various conditions were explained in terms of the solid-solution characteristics of KNN system, based on the high temperature phase diagram. The relationship of processing parameter-microstructure-property established herein will lead to further improvements in the piezoelectric properties of KNN lead-free materials. [ABSTRACT FROM AUTHOR]

• Flash butt welding of high-strength low-alloy steel was physically simulated. • The effect of upset allowance (δu) on the welds was systematically revealed. • A modest δu enables the welds to rival the mechanical properties of base metal. • Exaggerated δu deteriorates both the weld formability and mechanical properties. Flash butt welding (FBW) of high-strength low-alloy steel was physically simulated by the thermomechanical simulator and the influence of upset allowance (δu) on the microstructural and mechanical evolution of the welds was revealed. A moderate increase in δu from 3.5 to 6.5 mm will increase the amount of acicular ferrite and bainite ferrite with finer size in the weld zone, and also provide sufficient plastic deformation and proper dynamic recrystallization, paving the way to obtain excellent strength and plasticity being compatible with that of base metal. The findings will provide valuable references for the practical FBW process. [ABSTRACT FROM AUTHOR]

The dissimilar welded joints of Q&P980 and Q&P1180 steels with and without paint-baking heat treatment were investigated and their microstructures were characterized using confocal laser scanning microscope (CLSM), electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM) in order to understand the change of mechanical performances of the welded joints. The two Q&P steels have slight differences in compositions, but the obviously varying fraction of tempered martensite and thus the difference in the tensile strength. Prior to paint-baking heat treatment, the dissimilar welds exhibit a lower martensite fraction of the intercritical heat-affected zone (ICHAZ) in the Q&P980 side compared to the Q&P1180 side, and it is not affected by the paint-baking treatment. After the treatment, the occurrence of carbides and the coarsening of martensite in the whole welded joint, as well as the decomposition of retained austenite in the ICHAZ, are observed. The paint-baking treatment also causes the decreasing microhardness values of all regions. Especially, the significantly decreasing microhardness in the fusion zone compared to other heat-affected zones results in a partial pull-out failure mode compared to a full pull-out failure mode without paint-baking treatment. The change in failure mode and the softening of the martensitic matrix are found to be responsible for the increase in the peak load and the energy absorption of the dissimilar welded joint of Q&P980 and Q&P1180 steels. • Microstructures of the dissimilar welded joints of Q&P980/Q&P1180 were characterized. • Paint-baking treatment improved the mechanical performance of the dissimilar welded joints. • The failure mode of the dissimilar welded joints changed after the paint-baking treatment. • The significantly decreasing microhardness in the fusion zone was caused by the paint-baking treatment. • The mechanism of increasing the mechanical performance of the dissimilar welded joints was proposed. [ABSTRACT FROM AUTHOR]

• It is difficult to weld austenitic welding wire by MIG. • The grain boundary wetting phase transformations are explained. • The properties of deposited metal and welded joints are excellent. • A small amount of N 2 in the shielding gas can improve the weld performance. • This technology can be used for automatic welding and has broad prospects. Two different shielding gases, Ar + CO 2 and Ar + He + N 2 , were used for MIG welding of a 20 mm 10CrNi3MoV steel plate. The effects of shielding gases on the chemical composition, microstructure, purity, and low-temperature impact toughness of weld metal were studied in detail. N-containing shielding gas can increase the nitrogen content in the weld metal, change the solidification mode of deposited metal, reduce ferrite content in the weld metal, and significantly improve the low-temperature impact toughness of deposited metal. The purity of weld in the ternary inert gas atmosphere is high, which is beneficial to the improvement of low-temperature toughness. The ferrite content of the ternary joint is higher than that of the binary joint, and the strength of the ternary joint is much higher than that of the binary joint. [ABSTRACT FROM AUTHOR]

The correlation between microstructure evolution, texture development and hot deformation behavior of high manganese steel for LNG were investigated through uniaxial hot tensile tests at different temperatures (800, 850, 900 and 980 °C). Hot tensile tests were carried out on a Gleeble 3800 thermomechanical simulator with a strain rate of 10 /s. Texture analysis was conducted by the orientation distribution functions acquired from the electron backscatter diffraction (EBSD). Detailed microstructure and dynamic recrystallization (DRX) were indicated by the grain orientation spread of EBSD and transmission electron microscopy (TEM). The results show that there are only two stages in the work hardening rate when the deformed microstructure is non-recrystallized or mostly recrystallized. The work hardening rate exhibits a wave-like fluctuation when the tensile temperature is near the critical DRX temperature, due to the continuous competition between the dislocation packing caused by deformation and the softening intrigued by DRX. The deformed microstructure contains the highly dense dislocation wall (HDDW) structure and the cell block structure, and the HDDW structure mostly occurs in the 〈001〉//td fiber while the latter corresponds to the 〈111〉//td fiber. What's more, <001>//td fiber has stronger orientation gradient and work hardening rate than <111>//td fiber. DRX preferentially nucleated on the <001>//td fiber through two nucleation methods: strain-induced grain boundary migration and twining nucleation. DRX grains only retain the weak {111} 〈112〉 F and {110} <112> A textures, and the overall texture was weakened and randomized. • The highly dense dislocation wall occurs in the <001>//td fiber while the cell block corresponds to the <111>//td fiber • <001>//td fiber has stronger orientation gradient and work hardening rate than <111>//td fiber • DRX preferentially nucleated on the <001>//td fiber through strain-induced grain boundary migration and twining nucleation • The work hardening curve has a fluctuating characteristic near the critical recrystallization temperature [ABSTRACT FROM AUTHOR]