M. J Li
,
G.S. Song
,
G.C. Yang and YH Zhou (State Key Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
Fe-30at.%Co alloy is undereooled to investigate the effct of remelting on the grain size at certain undereooling rnnges. At low undereoolings, the primary stable fcc phase is remelted, which results in the equiaxed grains. When the melt is undercooled greater than the critical undereooling △T=204K the primary metastable bcc phase will alternatively nucleate in the melt. The primary bcc dendrite will be remelted into isolated dendrite cores dispersing in the remaining liquids. In the meanwhile, the isolated dendrite cores are remelted more or less due to the temperature fluctuation in the liquids. Different crystal structures between bcc and fcc phase make the subsequent crystal growth of fcc phase onto the Primary bcc phase non-epitaxial when the melt is undereooled greater than △T=204K. The primary metastable bcc phase may play an important role in coarsening grains in the systetn at larpe undereoolings.
关键词:
undercooling
,
null
,
null
,
null
Communications in Theoretical Physics
By using the theory of pressure-induced shifts and the eigenfunctions at normal and various pressures obtained from the diagonalization of the complete d(3) energy matrix adopting C-3v symmetry, g factors of the ground state of ruby and their pressure-induced shifts have been calculated. The results are in very good agreement with the experimental data. For the precise calculation of properties of the ground state, it is necessary to take into account the effects of all the excited states by the diagonalization of the complete energy matrix.
关键词:
crystal fields;g factors;ruby;high-pressure effects
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
The microstructural evolution during solidification and subsequent solid-state transformation of AISI 304 stainless steel is studied by directional solidification and quenching methods in this paper. The phase transformation sequence in the steel directionally solidified is that the precipitation of primary ferritic dendrites, ferrite-austenite eutectic reaction, and the direct formation of austenite occur in sequence during the directional solidification of the austenitic stainless steel. At the eutectic reaction stage, plenty of columnar and cellular eutectic colonies composed of the coupled growth of lamellar ferrite and austenite take place. During the course of subsequent solid-state transformation, austenite grows into ferrite gradually, resulting in the disappearing of eutectic colonies and thinning of primary ferritic dendrites, and dendrite cores of primary ferrite are retained as the final skeletal ferrite in the final microstructure. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
austenitic stainless steel;directional solidification;eutectic colony;austenitic stainless-steel;cr-ni alloys;sequence;welds
Wenjing Yao
材料科学技术（英）
The liquid-solid transitions of (Co2Si+CoSi) and (CoSi+CoSi2) eutectic alloys were realized in drop tube and the rapid eutectic growth mechanism of intermetallic compounds was examined. The experimental and calculated results indicate that with increasing Co content, the intermetallic compound prefers nucleating primarily. The eutectic microstructures experience the transitions of `lamellar-anomalous-divorced' eutectic with undercooling. In undercooled state, the growth of CoSi intermetallic compound always lags behind others, and no matter how large the undercooling is, this intermetallic compound grows under the solutal diffusion control. The calculated coupled zone demonstrates that (Co2Si+CoSi) eutectic can form within certain undercooling regime, when the composition is in the range from 23.6% to 25.4% Si. And the calculated coupled zone of (CoSi+CoSi2) covers a composition range from 40.8% to 43.8% Si.
关键词:
Liquid-solid transition
R.Shi
,
G.X.Hu
,
H.J.Li and M.K.Kang (The State Education Commission Open Research Laboratory for High Temperature Materials and Testing
,
Shanghai Jiao Tong University
,
Shanghai 200030
,
China)(Department of Materials Science and Engineering
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
The steady-state creep behavior of unidirectional C/C(1-D-C/C) composite with pyrolytic carbon matrix was investigated at high temperatures up to 2160℃ and under tensile stress from 133.83 to 213.46MPa. Based on the creep experiment of single specimen method, the apparent activation energy and the stress exponent for steadystate creep were determined by the use of a self-made apparatus and an auto-testing system. Value of apparent activation volume is provided and the creep mechanism has also been discussed.
关键词:
1-D-C/C
,
null
,
null
ZHANG Wei
,
YU Yan
,
FANG Yuan
,
LI Jian-guo
钢铁研究学报(英文版)
For many rapid or near-rapid solidification processes, the interfacial heat transfer between the melt and the substrate is a key issue on the cooling and solidification rate of castings. For the purpose of controlling and adjusting of the interfacial thermal resistance, the effects of C/BN, Zn and organic coatings on the instantaneous interfacial heat flux and the solidified structure of AISI304 stainless steel solidification on copper substrate have been investigated by using an experimental simulator. The results show that C/BN coatings can improve the uniformity of heat flux and solidified structure; Zn coating can increase the heat flux and solidification rate in the growth stage of the solidified shell; organic coating will decrease the heat flux and the solidification rate and make re-melted structure on the surface of the solidified shell.
关键词:
near rapid solidification
,
interfacial heat transfer
,
coating
Corrosion Science
The early stages of the evolution of atmospheric corrosion of carbon steels exposed in both a laboratory simulated and a natural atmosphere environment in Shenyang have been observed by in situ scanning electron microscopy. In the case of laboratory cyclic wet-dry tests, even though the chloride content level is very low, filiform corrosion is initiated in the early stage. The filiform corrosion grows in random directions, forming a network of ridges. White nodules nucleate and grow on the ridges during continued corrosion and eventually connect with each other to form the initial corrosion scale. Pits were also found on the surface beneath corrosion products. In the case of a natural atmospheric environment, both filiform corrosion and other localized corrosion, such as pitting and inter-granular attack take place in the initial stage. It is obvious that there is variety of localized corrosion in the initial stage of atmospheric corrosion. (C) 2007 Elsevier Ltd. All rights reserved.
关键词:
steel;atmospheric corrosion;initial stage;localized corrosion;in-situ;iron;electrolyte;thickness
