Shuigen HUANG
,
Lin LI
,
O.V.D.Biest
,
J.Vleugels
,
Peiling WANG
材料科学技术（英）
Using compound energy model (CEM), the thermodynamic properties of and were evaluated. The evaluation was based on the optimization of ZrO2-CeO2 and ZrO2-CeO1.5 systems, as well as the miscibility gap in CeO1.5-CeO2 system. Except the cubic fluorite structure phase assessed with compound energy model, all the other solution phases were assessed with subsitutional solution model. The model parameters were evaluated through fitting the selected experimental data by means of thermodynamic optimization. A set of parameters with thermodynamics self-consistency was obtained and satisfactorily described the complex relation between y in and the partial pressure of oxygen at different temperatures, also the interdependence among miscellaneous factors such as temperature, oxygen partial pressure, the reduction amount of CeO2 as well as the nonstoichiometry in cubic phase . The calculated results seem to be reasonable when put into the explanation of pressureless sintering of CeO2-stabilized ZrO2 powder compacts at a controlled oxygen partial pressure.
关键词:
Zirconia
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null
,
null
,
null
Shuigen HUANG
,
Lin LI
,
J.Vleugels
,
O.V.D.Biest
,
Peiling WANG
材料科学技术（英）
The ZrO2-CeO2-Al2O3 system has been assessed with the CALPHAD (Calculation of Phase Diagrams) technique using the PARROT procedure. The experimental information on the ZrO2 -Al2O3, Al2O3-CeO2 systems as well as the isothermal sections of the ternary system at 1673 K and 1873 K is well reproduced. According to the assessed isothermal section at 1723 K, no alumina dissolves into the tetragonal zirconia phase. Specimens with different alumina content are fabricated from commercial 12 mol pct CeO2-stabilized ZrO2 powder (12Ce-ZrO2). The thermodynamic properties are consistent with the observed microstructure, which present a combination of tetragonal phase and alumina grains.
关键词:
Ce-TZP
,
null
,
null
Xinbin HU
,
Mei ZHANG
,
Xiaochun WU
,
Lin LI
材料科学技术（英）
Based on the local equilibrium assumption, coarsening behavior of M23C6 carbide at 700℃ in H13 steel was simulated by DICTRA software. The results from the calculations were compared with transmission electron microscopy (TEM) observations. The results show the interfacial energy for M23C6 in H13 steel at 700℃ is thus probably 0.7 J•m-2, which fits the experiments well. The influence of composition and temperature on the coarsening rate was also investigated by simulations. Simulations show a decrease in the coarsening rate when V/Mo ratio is increased, while the coarsening rate increases with increasing temperature.
关键词:
DICTRA Simulation
,
碳化物粗化
,
界面能
,
H13钢
Weiyan LÜ
,
Lin LI
,
Li WANG
,
Yanlin HE
,
Shuigen HUANG
材料科学技术（英）
Phase diagram information of the Fe-C, Fe-Al and Al-C systems are reviewed and the Fe-Al-C system is assessed. A FeAlC database is created by combining a set of thermodynamic parameters established by Kumar and SSOL database in Thermo-Calc software package. Ternary phase diagrams are calculated with FeAlC and the newly developed Thermo-Calc databases SSOL2 and SSOL4. The FeAlC database is the best one to describe the Fe-Al-C system. A1 and A3 values on the vertical section containing 1.5 wt pct Al are calculated with the FeAlC database in this work. To validate the thermodynamic calculation, critical temperatures Ac1 and Ac3 are determined by using dilatometer analysis. There exist some errors between the calculated values and the experimental results. So further optimization of the Fe-Al-C system regarding bcc and fcc phases is necessary. The experimental data in this work could be of some value in further optimization.
关键词:
Fe-Al-C
,
null
,
null
Shuigen HUANG
,
Lin LI
,
J.Vleugels
,
O.V.D.Biest
材料科学技术（英）
The phase constitution of a composite consisting of 12 at. pct CeO2-3 at. Pct Y2O3-ZrO2/2.5 wt pct Al2O3 (3Y12Ce2.5Al) was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase and 63.1 at. pct tetragonal phase at 1450℃. Green compacts were fabricated by cold isostatic pressing with powder synthesized by coating technique, and pressureless sintered at 1450℃. The fracture toughness and Vickers hardness, evaluated by the micro-indentation method, are 2.02 MPa·m1/2 and 11.395 GPa, respectively. The addition of 3 at. pct Y2O3 to 12 at. Pct CeO2-ZrO2 ceramic leads to drastically decrease in toughness compared to composites without yttria stabilizer. No monoclinic phase is detected on the surface of all the ground samples. The high content of cubic phase and lack of phase transformation can be attributed to the low toughness based on the thermodynamic prediction.
关键词:
Thermodynamics
,
null
,
null
Yanlin HE
,
Lin LI
,
Xiaochun WU
,
Patrick WOLLANTS
材料科学技术（英）
The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.
关键词:
Prehardened-mould steel for plastic
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null
,
null
,
null
