Functional Materials Research II

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Authors: Heng Zhao, Qing Bin Liu, Gang Lee, Da Wei Yao
Abstract: The Inconel 718 alloy owes high strength and ductility at high temperature due to precipitation strengthening. In order to upgrade productility of Inconel 718 alloy, the Inconel 718 alloy solve hot crackings through Zr additions. The result shows that, the Inconel 718 alloy with Zr addition achieves grain size refinement and homogenization effect. It is suggested that, homogenization process, such as temperature point and time control, realizes low content of Nb segregation which is the key to prevent hot crackings. At the same time, through dendrite space measurement, the grain refinement realize high productivity of forged Inconel 718 alloy, as a another method of soft effect. In conclusion, adding Zr element is one of dominant methods for producing high quality of Inconel 718 alloy.
Authors: Tie Ye, Ping Yang, Zhi Wen Lu, Chun Hua Ma
Abstract: The organizations and phase composition after forging and heat treatment of the stacking fault energy for the three high manganese steel with 2.99 mJ/m2,7.9 mJ/m2and23 mJ/m2 were observed. It’s analysised that the microstructure and orientation change of three high manganese steel by SEM and EBSD and the effect of alloy elements and the composition of the material on microstructure of high manganese steel; Through Static compressive deformation of cylindrical specimen under different strain rates experimental, the effect of strain rate on the deformation mechanism of different components of high manganese steel was analysised. Cylindrical specimens by static compression at different strain rates, analysis of strain rate on the different components of high manganese steel impact deformation mechanism; The mechanical performance characteristics are analyzed under different strain rate of three components high-manganese steel by stress - strain curves. By Compressive Split-Hopkinson Pressure Bar experiments to study the mechanism of high manganese steel deformation at high strain rates. The study found: the exclusion of the impact of the martensitic transformation can produce 18Mn high manganese TRIP or TWIP effect after deformation. Through observation and calculation, it found C, Al's content of alloying elements on the grain sizes less affected, but the starting temperature of martensitic transformation and layer greatly affects high manganese wrong size possible. Through analysis, found C, Al decides that the high content of alloying elements manganese organization original phase composition and deformation mechanism; organizations γ + ε-M + α'-M high manganese TRIP effect occurs, organizations γ + ε-M's high manganese TRIP effect occurs, tissue TWIP effect of high manganese steel γ.
Authors: Jian Jian Yang, Hua Yan
Abstract: In this rsearch, MRFs with different viscosities were prepared. The friction and wear behaviors of carbonyl iron-based MRFs were investigated on a four-ball machine. In addition, the microscopic changes of surfaces were investigated by using scanning electron microscopy (SEM) to interpret the possible friction and wear mechanisms of MRF.It is found that the friction reducing and anti-wear properties are improved by increasing the viscosity of base oil and SiO2 content. Additionally, the operating sequence of sample injection and loading affects the entrainment of iron particles in the sliding surface.
Authors: Chao Fang, Yin Sheng He, Keun Bong Yoo, Jine Sung Jung, Kee Sam Shin
Abstract: Effects of welding and long-term service on the microstructural evolution of superheater tubes of TP347H stainless steel used in power plants were investigated by optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscope (TEM). Analyses after welding or long-term service, showed fine NbCs in grains, which will precipitaion strengthen the matrix. When TP347 was long-term serviced in power plants, M23C6 formed preferentially on the grain boundaries and on twin boundaries, which was attributed to the embrittlement and the intergranular corrosion and fracture. The steam side had less recrystallization rate and more oxide compared to the fire side, which is part of the reason for the cracking from steam side to the fire side. And HAZ is more brittle than the matrix, because of α-Fe phase and coarse grains, due to which, cracks tend to initiate in the steam side of HAZ and propagate to the fire side.
Authors: Hou Yu Ma, Yin Sheng He, Kwon Yeong Lee, Kee Sam Shin
Abstract: 13Cr martensitic stainless steels are widely used in gas industry, which are usually manufactured by quenching-tempering treatment. Microstructural study of 13Cr steel through various heat treatments was carried out for determining the optimum parameters for industry manufacture. After quenching treatment at 975 °C for 20 min, precipitation-free martensitic structures were formed. During tempering, recovery of martensite through grain boundaries migration and dislocations annihilation was found to soften the steel. In addition, transformation of needle-like Cr7C3 carbides to the irregular shaped Cr23C6 carbides was observed when tempering temperature is above 710 °C. The phase transformation induced precipitation strengthening is discussed. The optimum heat treatment parameters of 13Cr steel for avoiding over tempering and the precipitation hardening are found.
Authors: Kyeon Gae Nam, Yin Sheng He, Jung Chel Chang, Kee Sam Shin
Abstract: The Nb-stabilized and Cu-strengthened austenitic stainless steel Super304H was aged at 600~700°C up to 20,000 hrs. Scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to study the effect of aging on the microstructural evolution of the specimen, with focus on the precipitation behavior in relation to the temperature and time. Only NbCs in size range 2 μm ~ 50 nm were observed to be scarcely distributed in matrix in the as-received specimen. Upon aging, precipitation of σ-phase (~5 μm) and Cr-rich M23C6 (~1 μm) along grain boundary, and nanosized Cu precipitates (~65 nm) in the grain interior were formed. The size and fraction of the σ-phase and M23C6 increased with the increase of aging temperature and/or aging time, with higher sensitivity to the temperature. The size of Cu precipitates was relatively stable, while the fraction and number density increased with the aging temperature/time. The microhardness upon aging increased with increase of aging temperature/time, due to the precipitation of the nanosized Cu precipitates.
Authors: Wen Jing Wang, Xue Feng Liu
Abstract: Surface treated copper foil and its preparation is very important and widely used. The science research and enterprise competition always focus on the surface treated methods in the copper foil field. This paper summarized the typical surface treated processes of copper foil, and emphasized on research progress and problems of copper foil surface treated processes. The brush plating-dealloying treated process of copper foil was proposed based on the problems. The principle and research status of new process was introduced. At last, the future development of surface treated process and application prospect were forecast.
Authors: Yin Sheng He, Jung Chel Chang, Jeh Yun Lee, Kee Sam Shin
Abstract: The P92 steels were aged at 632°C for 500hrs and 1,000hrs, and creep ruptured at 650°C~625°C with stress of 120~110 MPa. The creep rupture life (CRL) of the aged samples was decreased with the aged time. The microstructure of the P92 steel was observed as fine tempered lath with dispersion of Cr-rich M23C6 along various grain boundaries. Upon aging and creep, recovery of lath and precipitation of coarse W-rich Laves phase were characterized as the main microstructural change. The M23C6 is relatively stable upon the short-term aging and creep. Decrease of the CRL of the aged specimens is considered as the degradations of microstructure such as the recovery of lath due to the dislocation annihilation and precipitation of coarse Laves phase.
Authors: Wen Long Jiang, Wei Zhou, Ji Fei Ying, Kong Chao Shen, Xing Yu Gao, Fu Qiang Guo, Yan Ming Gao, Tie Ying Yang
Abstract: In this paper, the anticorrosive properties of perfluorooctanoic acid (PFOA) on Q235 mild steel corrosion were estimated in simulated seawater. XRD and EDS results showed that PFOA could penetrate the rust layer and adsorb on the surface of steel and destroy rust layer. Our polarization measurements revealed that PFOA is a useful inhibitor, with a more pronounced anode effect, while impedance results also indicated successful adsorption of the PFOA species on the steel surface. Laser confocal scanning microscope studies give the evidence that corrosion resistance of the treated samples improved compared to the untreated samples. Molecular simulation technique was used to confirm the ability of PFOA to decrease corrosion. The 150 g/L concentration of PFOA showed the most significant improvement in the anticorrosive property.

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