Yanqing SU
,
Jingjie GUO
,
HongSheng DING
,
Songqing LIU
,
Yuan LIU
,
GuiZhong LIU
,
Jun JIA
材料科学技术（英文）
How to control melt composition is the key for getting high quality alloy melt. The paper made the following efforts: (1) The activity coefficients in Ti-15-3 melt have been calculated. (2) Taking advantage of the activity coefficients, the evaporation losses of components in Ti-15-3 melt during ISM process have been studied. The calculated results show that there is a critical vacuum degree (about 1.33 Pa) during melting process.
关键词:
Yanqing SU
,
Tiejun ZHANG
,
Jingjie GUO
,
Hongsheng DING
,
Weisheng BI
,
Jun JIA
,
Hengzhi FU
材料科学技术（英文）
Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.
关键词:
Traveling magnetic field
,
null
,
null
,
null
Wenbin SHENG
,
Dong LI
,
Rui YANG
,
Yuyin LIU
,
Jingjie GUO
,
Jun JIA
材料科学技术（英文）
Ti-48Al-2Cr-2Nb automobile exhaust valves were formed with permanent mold centrifugal cast method and their surface layer structure, microstructure, elements distribution and mechanical properties were analyzed by SEM, XRD and EMPA etc. Furthermore, the HIPped valves were tested on 483Q diesel engine. Results showed that the element distribution of TiAl based alloy exhaust valves was uniform and their microstructure was refined. The typical mechanical properties of HiPped exhaust valves were sigma (b)=670 MPa, sigma (0.2)=527.5 MPa and delta =3%. Engine test showed that the valves had excellent airtightness and wear resistance properties and satisfied the requirements of engine successfully.
关键词:
Yuan LIU
,
Jingjie GUO
,
Yanqing SU
,
Hongsheng DING
,
Jun JIA
材料科学技术（英文）
Melt spinning rapid solidification technique was employed to fabricate homogeneous Al-In immiscible alloys and their final microstructures and morphologies were investigated. There existed a transition of columnar Al grain®equiaxed grain for the thicker ribbon, butonly columnar Al grain for the thinner ribbon throughout the thickness. In the columnar grain field, most of the fine In particles was distributed within the cells, but a minority of bigger In particles or short rods was perpendicularly distributed at the grain boundaries. In the equiaxed grain field, the fine In particles were located in Al grains and coarser particles were situated at the boundaries. The average particle size increased with increasing distance from the chilled surface throughout the ribbon. At the same wheel speed (same cooling rate), the average particle size increased with raising In content. At the same composition condition, the average particle size decreased with increasing wheel speed and/or decreasing ejection temperature.
关键词:
Al-In immiscible alloy
,
null
,
null
Yuan LIU
,
Yanxiang LI
,
Jingjie GUO
,
Jun JIA
材料科学技术（英文）
Immiscible alloys are attractive for their valuable physical and mechanical properties. In this paper, Al-In immiscible alloy is prepared by melt spinning process and its morphological evolution is studied at various indium contents. The results show that the morphologies of the matrix phase depend on the indium content. Different morphologies lead to different distribution of the second phase particles. Due to a particular solidification mechanism of immiscible alloys, even under the melt spinning rapid solidification condition, it is still impossible to produce homogeneous Al-In hypomonotectic alloy ribbons. But for Al-In hypermonotectic alloys, there is almost no segregation of the second phase throughout the cross section of the ribbons.
关键词:
Immiscible alloys
,
null
,
null
Guizhong LIU
,
Jingjie GUO
,
Yanqing SU
,
Jingzhe GUO
,
Jun JIA
,
Hengzhi FU
材料科学技术（英文）
In this paper, the critical pressure pcrit and impeding pressure pimpe of the elemental evaporation were defined and studied based on the calculation of the relationship between the evaporation loss rate Nm and the chamber pressure p during melting of NiAl alloys. When the chamber pressure is lower than pcrit or higher than pimpe, Nm tends to be the maximum or minimum value and remains almost unchanged. However, declines sharply with the increase of the chamber pressure when pcrit
关键词:
ISM process
,
null
,
null
,
null
Wenbin SHENG
,
Jingjie GUO
,
Yanqing SU
,
Hongsheng DING
,
Jun JIA
材料科学技术（英文）
A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48Al-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.
关键词:
