CHEN Shu-ying
,
YUE Xu-dong
,
JIN Guang-can
,
LI Qing-chun
,
CHANG Guo-wei
钢铁研究学报(英文版)
The behavior of inclusions in the process of δ-phase growth during the solidification of Fe-015C-08Mn steel was in-situ observed using a high-temperature confocal scanning laser microscope (HTCSLM). The results show that inclusions arrive the S/L (solid/liquid) interface by way of direct impact or gradual drift, when the cell spacing is approximately equal to 177 μm during the growth of cellular δ-phase. The inclusions easily stay at the positions of trailing vortex formed by the circumferential motion of molten steel around δ-phase. Some inclusions reaching the S/L interface are captured by the solid-phase. Some of them move along the normal direction of the S/L interface because of pushing of solid-phase, and the others get away from the S/L interface after being pushed for a distance. The faster the growth rates of the solid-phase are, the easier the inclusions are captured by the S/L interface. The slower the growth rates of the solid-phase are, the easier the inclusions move with the S/L interface.
关键词:
inclusion
,
in-situ observation
,
carbon steel
,
solidification process
,
behavior
CHANG Guo-wei
,
CHEN Shu-ying
,
LI Qing-chun
,
YUE Xu-dong
,
JIN Guang-can
钢铁研究学报(英文版)
Abstract： Growth process of δ-phase was studied during the solidification of carbon steel. Through analyzing the solute diffusion around cylindrical crystals in the melt, the mathematic representation of lateral growth rate of cylindrical crystals was confirmed; the calculation and analysis of lateral growth rate were carried out. In order to validate the theoretical calculation and analysis, the growth process of δ-phase during the solidification was in-situ observed using a confocal scaning laser microscope (CSLM) and the growth rates were measured through CSLM images. The results show that lateral growth rates of δ-phase in the carbon steel first rapidly decrease with the increase of the radius of the cylindrical crystal, and then slowly fall down or maintain invariable. The radius of δ-phase is the primary factor to affect the growth rate. The higher the temperature gradient is, the bigger the growth rate is. However, the effect of the temperature gradient is feeble. Good correlation is obtained between theoretical analysis and experiment results in absolute values of lateral growth rate and change rule.
关键词:
Key words: cell growth
,
solidification process
,
carbon steel
,
in-situ observation
Her-Yueh Huang
,
Kuang-Hung Tseng
金属学报(英文版)
The effects of the process parameters on the joint quality of TO-Can using resistance projection welding were investigated. A capacitor discharge stored energy welding machine was used for joining caps and headers both coated with nickel SPCC steel. The electrode materials used in this study were brass and W- Cu alloy. Experimental results indicated that the peak current of the W-Cu electrode was higher than that of the brass electrode, irrespective of the operating pressure variation. Increased operating pressure influenced the interfacial heat generation and nugget formation. The nugget area increased rapidly with increasing charging voltage, resulting in expulsions and electrodes getting stuck. An acceptable welding zone was found in the relationship between the charging voltage and the operating pressure. Representative test specimens of the acceptable welding zone satisfactorily passed the helium leak test. The microscopic morphology of the nugget showed a recrystallized fine grain structure resulting in the nugget being harder than with the HAZ.
关键词:
Projection welding
Journal of Physics-Condensed Matter
Recent theoretical studies indicate that metastable rocksalt CaN, SrN, and BaN exhibit half-metallic ferromagnetism (Volnianska and Boguslawski 2007 Phys. Rev. B 75 224418; Gao et al 2008 Phys. Lett. A 372 1512), and further experiments confirm the existence of self-assembled metastable CaN nanostructures (Liu et al 2008 Surf. Sci. 602 1844). We here use the first-principles method based on density functional theory to investigate the structural, electronic, and magnetic properties of the (111) surfaces of CaN and SrN and the interfaces of CaN/InN(111) and SrN/GaP(111). The surface stability from the calculated surface energy indicates that the N-terminated (111) surface is more stable than the Ca (Sr)-terminated (111) surface in the N-rich environment. For CaN and SrN, both anion-and cation-terminated (111) surfaces preserve the half-metallic characteristics of the bulk. Interfacial studies indicate that the half-metallicity of bulk CaN is retained in two of the four possible configurations of the CaN/InN(111) interface, while for the interface of SrN/GaP(111) only one interfacial configuration shows half-metallicity. Furthermore, we assess the interfacial adhesive strength for all the possible different configurations of the interfaces studied here by calculating the interface adhesion energies.
关键词:
molecular-beam epitaxy;room-temperature;ferromagnetism;1st-principles
Journal of Materials Research
Three typical interactions of persistent slip bands (PSBs) with different types of grain boundaries (GBs) were investigated and analyzed in fatigued copper crystals. The results show that PSBs cannot transfer through all types of large-angle GBs, regardless of their orientation with respect to the stress axis. Secondary slip was often observed near the GBs, leading to strain incompatibility. When the slip systems of the two adjacent crystals are coplanar, the transmission of a PSB across a GB strongly depends on the slip directions of the two adjacent crystals. It was found that only the low-angle GBs can be passed through by PSBs, and accordingly they are insensitive to intergranular fatigue cracking. For a special copper bicrystal with coplanar slip systems, the ladderlike dislocation arrangements within the adjacent PSBs become discontinuous and a dislocation-affected-zone appears near the GB due to the difference in the slip direction of the two adjacent crystals. Therefore, the necessary conditions for the transmission of a PSB across a GB are that the neighboring grains have a coplanar slip system and identical slip directions.
关键词:
cyclic deformation-behavior;fatigued copper polycrystals;dislocation-structures;single-crystals;bicrystals;metals;zones
Y.H. He
,
B. Y. Huang
,
Y. Liu and Y.X. Liu (Powder Metallurgy Research Institute
,
Central South University of Technology
,
Changsha 410083
,
China)
金属学报(英文版)
The effects of a new technology, multi-step thermo-mechanical treatment, on the microstructure, deformation substructure and mechanical properties at ambient and elevated tempemture of can-forged Ti-33 Al-3 Cr-0.5Mo (wt%) Alloy were investigated.The results show that, after multi-step thermo-mechanical treatment of can-forged specimens, homogeneous, fine microstructures can be obtained in the whole TiAl-based alloy specimens. Furthermore, the specimen with homogeneous and fine full lamellae microstructure demonstrutes excellent comprehensive mechanical properties at ambient and elevated temperature.
关键词:
TiAl-based alloy
,
null
,
null
朱林晖
,
丁马太
功能材料
在研究玉米淀粉(corn starch,CS)与甲基丙烯酸甲酯(MMA)接枝共聚反应时发现,硝酸浓度为0.1mol/L、硝酸铈铵(CAN)/CS质量比为1/6、MMA/CS质量比为3/2是兼顾单体转化率(C)、接枝率(G)和接枝效率(GE)的最佳反应条件;同时发现,该反应中均聚物的生成不仅可由CAN直接引发,还可能因淀粉自由基或淀粉接枝物自由基的链转移而引发.
关键词:
淀粉
,
接枝共聚
,
硝酸铈铵
,
均聚物
G.S. Fu
,
W.Z. Chen
,
K.W. Qian
金属学报(英文版)
The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treatment during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble1500 dynamic hot-simulation testing machine. The results show that the Al sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500℃ at strain rates within the range of 0.01-10.0s-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at elevated temperature for this material is thermally activated. Compared with the Al pieces prepared by no or conventional melt-treatment, hot deformation activation energy of Al sheets prepared by high-efficient melt-treatment is the smallest (Q = 168.0kJ/mol), which reveals that the hot working formability of this material is very better, and has directly to do with the effective improvement of its metallurgical quality.
关键词:
Al sheets used for can
,
null
,
null
