Effect of Cr Addition on the Multiphase Equilibria in the Nb-rich Nb-Si-Ti System - Thermodynamic Modeling and Designed Experiments

2008 ◽  
Vol 1128 ◽  
Author(s):  
Ying Yang ◽  
Bernard P Bewlay ◽  
Shuanglin chen ◽  
M R Jackson ◽  
Y. A. Chang
Keyword(s):  
Phase Equilibria ◽  
Thermodynamic Modeling ◽  
Thermodynamic Description ◽  
Designed Experiments ◽  
Beneficial Effects ◽  
High Temperature Materials ◽  
Ti Alloys ◽  
Multiphase Equilibria ◽  
Cr Addition ◽  
Alloying Effects

AbstractRefractory Metal Intermetallic Composites (RMICs) based on the Nb-Si system are considered as candidates of next-generation high temperature materials (i.e. >1200°C). Ti and Cr have been shown to have beneficial effects on the oxidation resistance and mechanical properties of Nb-Si alloys. Phase equilibria in the Nb-Si-Ti system have been studied in detail. The present study has investigated multiphase equilibria in the Nb-Si-Ti alloys with Cr additions via an approach of integrating thermodynamic modeling with designed experiments. The alloying effects of Cr on the microstructure of the Nb-Si-Ti alloys are described using both phase equilibria and solidification paths that were calculated from the thermodynamic description of the Nb-Cr-Si-Ti system developed in the present study.

Phase Equilibria in the Nb-rich Nb-Ti-Si-Cr-Hf alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Ying Yang ◽  
Bernard P. Bewlay ◽  
Austin Chang
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Phase Equilibria ◽  
Calphad Approach ◽  
Rich Region ◽  
Isothermal Sections ◽  
Beneficial Effects ◽  
High Temperature Materials ◽  
Ti Alloys ◽  
Alloying Effects

ABSTRACTRefractory Metal-Intermetallic Composites (RMICs) based on the Nb-Si system have been considered as candidates for the next-generation high temperature materials (i.e. >1200°C). Ti, Cr and Hf have been shown to have beneficial effects on the oxidation resistance and mechanical properties of Nb-Si alloys. The present study has determined phase equilibria in the Nb-rich region of the Nb-Si-Ti-Cr-Hf system via the Calphad approach. The alloying effects of Cr and Hf on the microstructure of Nb-Si-Ti alloys are understood based on isothermal sections, liquidus projections, and solidification curves that were calculated from the thermodynamic models of the Nb-Ti-Si-Cr-Hf system developed in the present study. This work provides important guidelines on the development of new Nb-Si-Ti-Cr-Hf alloys.

Effect of Cr Addition on the Phase Equilibria of the Nb-Si System

2006 ◽  
Vol 980 ◽  
Author(s):  
B. P. Bewlay ◽  
Y. Yang ◽  
R. L. Casey ◽  
M. R. Jackson ◽  
Y. A. Chang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Phase Equilibria ◽  
Thermodynamic Description ◽  
Directionally Solidified ◽  
Isothermal Sections ◽  
Environmental Properties ◽  
Structural Applications ◽  
Cr Addition

AbstractNb-silicide based in-situ composites are promising materials for future high-temperature structural applications. Nb-silicide composites are typically alloyed with Hf, Ti, Cr, and Al to provide a balance of mechanical and environmental properties. A thermodynamic description of the Nb-Cr-Si system has been developed previously in literature based on reported isothermal sections. According to the previously calculated phase diagrams, selected alloys were directionally solidified. The as-solidified microstructures could not be interpreted using the liquidus projection calculated from the existing thermodynamic descriptions. Therefore, an improved thermodynamic description was developed by incorporating the new experimental data.

scholarly journals Irradiation Hardening Behavior of He-Irradiated V–Cr–Ti Alloys with Low Ti Addition

2020 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Ken-ichi Fukumoto ◽  
Yoshiki Kitamura ◽  
Shuichiro Miura ◽  
Kouji Fujita ◽  
Ryoya Ishigami ◽  
...  
Keyword(s):  
Ion Irradiation ◽  
Optimum Composition ◽  
Solid Solution Hardening ◽  
Irradiation Hardening ◽  
Hardening Behavior ◽  
Ti Alloys ◽  
Void Swelling ◽  
Before And After ◽  
Cr Addition ◽  
Ti Addition

A set of V–(4–8)Cr–(0–4)Ti alloys was fabricated to survey an optimum composition to reduce the radioactivity of V–Cr–Ti alloys. These alloys were subjected to nano-indenter tests before and after 2-MeV He-ion irradiation at 500 °C and 700 °C with 0.5 dpa at peak damage to investigate the effect of Cr and Ti addition and gas impurities for irradiation hardening behavior in V–Cr–Ti alloys. Cr and Ti addition to V–Cr–Ti alloys for solid–solution hardening remains small in the unirradiated V–(4–8)Cr–(0–4)Ti alloys. Irradiation hardening occurred for all V–Cr–Ti alloys. The V–4Cr–1Ti alloy shows the highest irradiation hardening among all V–Cr–Ti alloys and the gas impurity was enhanced to increase the irradiation hardening. These results may arise from the formation of Ti(CON) precipitate that was produced by He-ion irradiation. Irradiation hardening of V–Cr–1Ti did not depend significantly on Cr addition. Consequently, for irradiation hardening and void-swelling suppression, the optimum composition of V–Cr–Ti alloys for structural materials of fusion reactor engineering is proposed to be a highly purified V–(6–8)Cr–2Ti alloy.

Metastable phase equilibria in the lead-tin alloy system: Part II. Thermodynamic modeling

1989 ◽  
Vol 20 (5) ◽  
pp. 795-803 ◽  
Author(s):  
H. J. Fecht ◽  
M. X. Zhang ◽  
Y. A. Chang ◽  
J. H. Perepezko
Keyword(s):  
Phase Equilibria ◽  
Thermodynamic Modeling ◽  
Metastable Phase ◽  
Alloy System ◽  
System Part

Phase equilibria of the La–Ni–Cu ternary system at 673 K: Thermodynamic modeling and experimental validation

Calphad ◽  
2012 ◽  
Vol 36 ◽  
pp. 8-15 ◽  
Author(s):  
Xuehui An ◽  
Qian Li ◽  
Jieyu Zhang ◽  
Shuanglin Chen ◽  
Ying Yang
Keyword(s):  
Ternary System ◽  
Phase Equilibria ◽  
Thermodynamic Modeling ◽  
Experimental Validation

scholarly journals A thermodynamic description of metastable c-TiAlZrN coatings with triple spinodally decomposed domains

2017 ◽  
Vol 53 (2) ◽  
pp. 85-93 ◽  
Author(s):  
J. Zhou ◽  
L. Zhang ◽  
L. Chen ◽  
Y. Du ◽  
Z.K. Liu
Keyword(s):  
Experimental Data ◽  
Phase Equilibria ◽  
First Principles ◽  
Thermodynamic Description ◽  
Quantitative Description ◽  
Experimental Phase Equilibria ◽  
Free Energies ◽  
Calphad Technique ◽  
Important Input ◽  
Good Agreement

A critical thermodynamic assessment of the metastable c-TiAlZrN coatings, which are reported to spinodally decompose into triple domains, i.e., c-TiN, c-AlN, and c-ZrN, was performed via the CALculation of PHAse Diagram (CALPHAD) technique based on the limited experimental data as well as the first-principles computed free energies. The metastable c-TiAlZrN coatings were modeled as a pseudo-ternary phase consisting of c-TiN, c-AlN and c-ZrN species, and described using the substitutional solution model. The thermodynamic descriptions for the three boundary binaries were directly taken from either the CALPHAD assessment or the first-principles results available in the literature except for a re-adjustment of the pseudo-binary c-AlN/c-ZrN system based on the experimental phase equilibria in the pseudo-ternary system. The good agreement between the calculated phase equilibria and the experimental data over the wide temperature range was obtained, validating the reliability of the presently obtained thermodynamic descriptions for the c-TiAlZrN system. Based on the present thermodynamic description, different phase diagrams and thermodynamic properties can be easily predicted. It is anticipated that the present thermodynamic description of the metastable c-TiAlZrN coatings can serve as the important input for the later quantitative description of the microstructure evolution during service life.

scholarly journals Thermodynamic modeling of phase equilibria in the system Na2O – CaO – Al2O3

2019 ◽  
Vol 57 (2) ◽  
pp. 111-115
Author(s):  
Svetlana E. Pratskova ◽  
◽  
Evgenia S. Nechaeva ◽  
Keyword(s):  
Phase Equilibria ◽  
Optical Fibers ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Liquid Solution ◽  
Exothermic Effect ◽  
Regression Equations ◽  
Melt Mixing ◽  
Energy Parameters ◽  
State Diagrams

The thermodynamic properties of melts of the Na2O – CaO – Al2O3 system are of considerable interest for metallurgy, technology of ceramic materials, optical fibers. State diagrams CaO – Al2O3, Na2O – Al2O3 have been studied by many researchers and do not have the generally accepted version, and the system Na2O – CaO has not been specifically studied. In the work, thermodynamic modeling of the phase equilibria of the Na2O – CaO – Al2O3 system was carried out within the framework of the generalized theory of “regular” ionic solutions. Equations for the activities of the system components are derived. The energy parameters of the model are determined taking into account melting characteristics and experimental data. The state diagrams of binary systems are constructed using the calculated values of the Gibbs energies for the formation of sodium and calcium aluminates from the corresponding oxides. Using the regression equations of the temperature dependences of the energy parameters of binary melts of the Na2O – CaO – Al2O3 system, the molar mixing functions of the liquid solution раствора G_m^M, H_m^M, S_m^M and the excess thermodynamic functions G^E, H^E, S^E were calculated at 1500-1800 oC. Lime-alumina melts are stable at all temperatures, experiencing negative deviations from ideality. The Gibbs excess energy G^E is negative and in absolute value varies from 5 to 90 kJ/mol. With an increase in the concentration of Al2O3 in the melt and temperature, a tendency toward disorder is clearly manifested: the entropy of the melt mixing changes its sign from “minus” to “plus”. Na2O – Al2O3 melts are formed with an exothermic effect and ordering, and are also stable. They experience strong negative deviations (for G^E) from ideality. However, the situation changes at 55 mol. % Al2O3 and 1700-1800 oС melts of the system are unstable.

Alloying Effects on Reverse Transformation to Austenite from Pearlite or Tempered Martensite Structures

2010 ◽  
Vol 638-642 ◽  
pp. 3400-3405 ◽  
Author(s):  
Goro Miyamoto ◽  
Zhao Dong Li ◽  
Hirokazu Usuki ◽  
Tadashi Furuhara
Keyword(s):  
Decomposition Reaction ◽  
Reverse Transformation ◽  
Transformation Kinetics ◽  
Tempered Martensite ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Cr Addition ◽  
Alloying Effects ◽  
Kinetics Of ◽  
Martensite Structure

Reverse transformation has been frequently used to refine austenite grain size for refining ferrite, pearlite and martensite structures. However, kinetics and microstructure change during reverse transformation to austenite has not been examined systematically compared with the austenite decomposition reaction. Therefore, alloying effects of 1mass% Mn, Si and Cr on reverse transformation kinetics from pearlite and tempered martensite structures in Fe-0.6mass%C alloys were investigated in this study. Vickers hardness of all the specimens increases with increasing holding time at 1073K because reversely-formed austenite transforms to martensite by quenching. In the reverse transformation from pearlite structure, the kinetics of reverse transformation is hardly changed by the Mn addition while Si and Cr additions delay it. Kinetics of reverse transformation from tempered martensite structure becomes slower than from the pearlite structure in all the alloys. In particular, retarding effect by the Cr addition is most significant among those elements.

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