期刊：
Journal of Central South University of Technology,1996年3(2):122-134 ISSN：1005-9784
作者机构：
[Yuehui He; Qiuhua Rao] Central South University of Technology;[Yuhua Tan] Xiangtan University
摘要：
The effect of carbon content on the morphology of martensite in carbon steels has been studied in depth. It is found that not all the packet martensites obtained in carbon steels quenched from elevated temperature are lath martensite. The packet martensite obtained thus should be divided into two categories: packet thin plate martensite (i. e. lath martensite) and packet plate martensite. The former is only found in low carbon steels, the latter mainly in medium and high carbon steels. The morphology of martensite in steels with different carbon contents has been researched in detail using optical microscopy, SEM and TEM. A new criterion is proposed for identifying the category of martensite. Based on this new criterion, it is found that as-quenched steels withC c⩽0.2% contains lath martensite; that with 0.2%<C c<0.4% contains a mixture of lath and plate martensite. The structure of as-quenched steels withC c⩾0.4% is completely of plate martensite. The curve of the relative volume percentage of martensite without internal twins versus carbon content has been redetermined. Finally, the misinterpretation of experimental results by previous investigators is analysed.
期刊：
Transactions of Nonferrous Metals Society of China,1995年5(4):79-83 ISSN：1003-6326
通讯作者：
Huang, Baiyun
作者机构：
[He, YH; Huang, BY; Qu, XH; Kong, GN] CENT S UNIV TECHNOL,POWDER MET RES INST,CHANGSHA 410083,PEOPLES R CHINA.;null
关键词：
Fine full lamellar structure - Microstructure refining - Multistep thermomechanical treatment - Titanium aluminide
摘要：
A multi-step thermo-mechanical treatment (MSTMT) was developed to refine the microstructure of Ti-33Al-3Cr-0.5Mo(%) alloy. It was found that fine full lamellar structure can be obtained by appropriate procesing of MSTMT. Superior comprehensive mechanical properties can result from the full lamellar structure with homogeneous fine grain.
期刊：
Transactions of Nonferrous Metals Society of China (English Edition),1996年6(3):96-102 ISSN：1003-6326
通讯作者：
He, Yuehui
作者机构：
[He, Yuehui; Liu, Yexiang; Liu, YX; Huang, Baiyun] CENT S UNIV TECHNOL,RES INST POWDER MET,CHANGSHA 410083,PEOPLES R CHINA.;null
关键词：
TiAl based alloy;microstructure;mechanical property;heat treatment
摘要：
Owing to the limitation of the normal thermomechanical treatment on TiAl based alloy, a double-temperature heat treatment technology for hot forged TiAl based alloy was suggested. The effect of the new technology on microstructure and tensile properties of the alloy at ambient temperature was also studied. By TEM analysis, the mechanism that the double-temperature heat treatment improves the homogeneity of the microstructure in TiAl based alloy was discussed.
期刊：
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals,1998年8(Suppl):11-17 ISSN：1004-0609
作者机构：
[Huang, Baiyun; He, Yuehui; Peng, Chaoqun] Central South Univ of Technology, Changsha, China
摘要：
The main defects of the TiAl-based alloys were pointed out, i.e. inverse relations between tensile properties and fracture/creep resistance, relatively low high-temperature strengths for many of the turbine-engine parts in use up to 1 000 °C, concern about oxidation resistance above 800 °C, and the methods to solve these problems were proposed, i.e. alloying, hot working, heat treatment and coating and so on, and the emphasis was placed on the effects of alloying. The effect of alloying on phase equilibrium was analyzed. The effects of alloying on strength and ductility and its mechanisms were discussed.
期刊：
Transactions of Nonferrous Metals Society of China,1999年9(4):692-695 ISSN：1003-6326
通讯作者：
Tang, Jiancheng
作者机构：
[贺跃辉; 黄伯云; 谢鲲; 唐建成] Cent S Univ Technol, State Key Lab Powder Met, Changsha 410083, Peoples R China.
关键词：
TiAl based alloys;microstructure;nitrogen addition;grain refinement
摘要：
Through adding 0% to approximately 3% (mole fraction) nitrogen in cast TiAl based alloys, it was found that colony size in cast condition decreased from 600 μm to 58 μm with nitrogen content increasing from zero to 1% and then decreased slowly with further increase of nitrogen content, tensile strength increased with nitrogen content;but comparing to the value of the mother alloy, tensile elongation at room temperature decreased in the alloy with 0.5% nitrogen, then recovered in the alloy with 1% nitrogen.
摘要：
The influence of microstructures on the cyclic oxidation behaviour of Ti-33Al-3Cr-0.5 Mo(%) alloy was investigated. It was clarified that the oxidation behaviour of the alloy with near-gamma, duplex and fully-lamellar microstructure are very similiar in air at 1173 K and their mass gain is much lower than that of the alloy with nearly-lamellar microstructure. The reason for the difference in oxidation behaviours was attributed to the morphologies of Al2O3 layer in the oxide scale.
摘要：
The influences of Ca addition on the microstructure and room temperature mechanical properties of as-cast TiAl based alloy were investigated. The results showed that Ca addition could improve markedly the strength and ductility of TiAl at ambient temperature. Microstructure of Ca-doped TiAl alloy was dendric crystalline. Fracture mode of Ti-Al-Ca ternary alloy was a mixed mode, including cleavage cracks vertical to lamellar direction and ''river'' pattern in gamma single phase. In addition, a lot of tear ridges were found in the fractured surface.
期刊：
Transactions of Nonferrous Metals Society of China,2014年24(6):1730-1736 ISSN：1003-6326
通讯作者：
Liu, Y.(yonliu@csu.edu.cn)
作者机构：
[Liu Yong; Qiu Congzhang; Zhou Canxu; He Yuehui; Liu Bin] State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
通讯机构：
[Liu, Yong] Cent S Univ, State Key Lab Powder Met, Changsha 410083, Peoples R China.
关键词：
TiAl alloy;carbon doping;microstructure;carbide
摘要：
The effect of carbon addition on the microstructures of TiAl-based alloy (Ti-45Al-3Fe-2Mo) was studied. The proportion of β/B2 phase reduces with the content of carbon increasing, while the colony size increases. With increasing the carbon content, the lamellar spacing first decreases from 267 nm (Ti-45Al-3Fe-2Mo) to 237 nm (Ti-45Al-3Fe-2Mo-0.3C) and 155 nm (Ti-45Al-3Fe-2Mo-0.5C), but then increases to 230 nm (Ti-45Al-3Fe-2Mo-1.0C) with further increase in C level, which is affected by the inhibition of carbon atom and precipitation of carbides at the lamellar interface. Precipitation of carbides shows a response to aging time at 800 ℃. P-type carbides grow up at the boundaries and near the dislocation areas with the prolonging of aging time. And these carbides are projected different morphology in different beam directions (BD). The effects of these microstructural modifications were examined and the observations were discussed.
