SUN Zhengming
,
WANG Zhongguang
,
AI Suhua Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China. To whom correspondence should be addressed.
材料科学技术（英文）
Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-% martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.
关键词:
cyclic deformation
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MA Zongyi YAO Zhongkai Harbin Institute of Technology
,
Harbin
,
China
金属学报(英文版)
The SiC_w/Al composite prepared by squeeze casting has a combination of superior room temperature specific strength and modulus together with excellent thermal properties.The extrusion can make an improvement on the strength and ductility of the composite from 582 MPa as squeeze casted up to 639 MPa,and on the transformation from isotropic to the anisotropic structure.This seems to be explained by the orientation of whiskers and the densification of dislocations in matrix.TEM observation indicates that the stacking fault is the usual planar defect on the SiC_w surface. composite;;SiC whisker;;Al alloy;;microstructure
关键词:
composite
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Corrosion
This paper introduces the design of a localized corrosion rate monitoring instrument that can monitor and evaluate the maximum and stable localized corrosion rate of a nonpassivable metal in a corrosive environment by measuring the current density in a corrosion sensor with an occluded anode.
关键词:
instrument;localized corrosion rate;monitor
Juhua HUANG
,
Jinjun RAO
,
Xuefeng LI
材料科学技术（英文）
Sheet metal forming is widely applied to automobile, aviation, space flight, ship, instrument, and appliance industries. In this paper, based on analyzing the shortcoming of general finite element analysis (FEA), the conception of parametric finite element analysis (PFEA) is presented. The parametric finite element analysis, artificial neural networks (ANN) and genetic algorithm (GA) are combined to research thoroughly on the problems of process parameters optimization of sheet metal forming. The author programs the optimization scheme and applies it in a research of optimization problem of inside square hole flanging technological parameters. The optimization result coincides well with the result of experiment. The research shows that the optimization scheme offers a good new way in die design and sheet metal forming field.
关键词:
Sheet metal forming
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J.Q.ZHANGD.J.YOUNG
中国腐蚀与防护学报
Metaldusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400 ℃~1000 ℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising Fe3C but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting behaviour of engineering alloys is discussed.
关键词:
metal dusting
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Liang ZHEN Yuexian CUI Dezhuang YANG Department of Materials Science
,
Harbin Institute of Technology
,
Harbin
,
150006
,
ChinaShenglong DAI Guifu YU Beijing Institute of Aeronautical Materials
,
Beijing 100095
,
China
材料科学技术（英文）
The formation of precipitation free zone (PFZ) and its effect in a RSP AI-Li alloy has been studied. The results show that PFZ is easy to form when aged at 190℃,but there is no equilibrium phase on grain boundaries.The growth of PFZ in the alloy is different from that in conventional AI-Li alloys, The effect of PFZ is of great importance because of its large volume fraction in the alloy.It offsets the beneficial effect of RSP,and is thought to be an important factor that leads to the poor toughness and low ductility of RSP AI-Li alloy sheet.
关键词:
precipitation free zone
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Z. Yang
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J.P. Li
,
J.X. Zhang
,
G.W.Lorimer
,
J. Robson
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null
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null
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null
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null
金属学报(英文版)
The current research and development of magnesium alloys is summarized. Several aspects of magnesium alloys are described: cast Mg alloy, wrought Mg alloy, and novel processing. The subjects are discussed individually and recommendations for further study are listed in the final section.
关键词:
Magnesium alloys
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