ZHOU Zhao JI Shichen HU Zhuangqi SHI Changxu (C.H.Shih) Institute of Metal Research
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Academia Sinica
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Shenyang
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China
金属学报(英文版)
Study of the solidification process of both Al-Si and Al-Cu alloys proved the presence of acoustic emission phenomena.Two peaks of count rate have been observed.The total counts of both peaks increase with the increasing hydrogen content of the alloy.The mechanism of producing the acoustic emission has been discussed.At the same time,results obtained by oth- er techniques strongly support the good correlation between the acoustic emission and hydrogen releasing during solidification.The bubble nucleation between dendrite arms is the main cause of the first peak,while the fracture of the bridge connecting the interdendrites at the later stage of solidification is the main cause of the second peak.It is probably due to the hydrogen evolution and accumulation to create high pressure in the interdendritie region.
关键词:
aluminium ahoy
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MA Zongyi YAO Zhongkai Harbin Institute of Technology
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Harbin
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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
王君
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邹家桂
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陈政标
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高建武
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刘彦坤
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张杰元
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宋莎
绝缘材料
为解决苯乙烯和甲基苯乙烯在VPI浸渍树脂应用于风力发电机中的不足，采用不饱和聚酯亚胺、引发剂和无挥发活性稀释剂研制出116HU聚酯亚胺无挥发浸渍树脂，并对其各项性能进行了研究。结果表明：116HU聚酯亚胺无挥发浸渍树脂的常规性能满足风力发电机的要求，其耐热等级可达H级。用该树脂浸渍的风电模拟线棒具有优异的介电性能、耐湿热交变和高低温循环冲击性能及耐盐雾性能等，能满足风力发电机在极端环境运行的要求。
关键词:
聚酯亚胺
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无挥发
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VPI
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风力发电机
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耐湿热
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耐盐雾
Dental Materials
Objectives. To research the crystal structure and surface morphology of anodic films on titanium metal in different electrolytes under various electrochemical conditions and investigate the effect of the crystal structure of the oxide films on apatite-forming ability in simulated body fluid (SBF). Methods. Titanium oxide films were prepared using an anodic oxidation method on the surface of titanium metal in four different electrolytes: sulfuric acid, acetic acid, phosphoric acid and sodium sulfate solutions with different voltages for 1 min at room temperature. Results. Anodic films that consisted of rutile and/or anatase phases with porous structures were formed on titanium metal after anodizing in H(2)SO(4) and Na(2)SO(4) electrolytes, while amorphous titania films were produced after anodizing in CH(3)COOH and H(3)PO(4) electrolytes. Titanium metal with the anatase and/or rutile crystal structure films showed excellent apatite-forming ability and produced a compact apatite layer covering all the surface of titanium after soaking in SBF for 7 d, but titanium metal with amorphous titania layers was not able to induce apatite formation. Significance. The resultant apatite layer formed on titanium metal in SBF could enhance the bonding strength between living tissue and the implant. Anodic oxidation is believed to be an effective method for preparing bioactive titanium metal as an artificial bone substitute even under load-bearing conditions. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
关键词:
Titanium;Anodic oxidation;Rutile;Anatase;Apatite;simulated body-fluid;oxide-films;apatite formation;heat-treatments;surface;anodization;deposition;implants;coatings;ability
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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