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Phase Diagrams and Microstructure Evolution of Al-Cu-RE (RE=Y,Nd,Gd,Dy,Er,Yb and Ti) Alloys

Author: ZhangLiGang
Tutor: JinZhanPeng；LiuLiBin
School: Central South University
Course: Materials Science
Keywords: Al-Cu - RE CALPHAD technology Alloy design Equilibrium phase diagram Solidification simulation Glass-forming ability
CLC: TG146.21
Type: PhD thesis
Year: 2010
Downloads: 401
Quote: 1
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Abstract

Aluminum due to its light weight, high strength and good corrosion resistance, excellent performance and its applications in the aerospace, causing widespread concern in the international materials and industrial sectors. Adding rare earth aluminum alloy, can significantly improve the alloy's mechanical properties, physical properties and processing performance. Through the formation of amorphous preparation of high-performance rare earth aluminum alloy, especially rare earth aluminum alloy amorphous forming ability is a hot research topic in the materials sector emerging. This paper combines the National Natural Science Foundation of China (No.50771106): phase diagram and micro-alloying of Al-Cu alloy system, part of the Al-Cu-Y-Nd-Gd-Dy-Er-Yb-Sb-Ti system Department of binary, ternary system, and to simulate the evolution of typical ternary Al-Cu-RE alloys organization, Driving forces criterion to predict the glass-forming ability and subsequent crystallization tendency (sequence), initially built one kind of Al-Cu-RE alloy system design methods, and try to use the method of analysis of a U.S. patent, the following main results: (1) alloying, with the help of metallographic, scanning electron microscopy (SEM) and X - ray diffraction (XRD) analysis and other means of detection and analysis, determination of the phase composition of the Cu-RE (RE = Y, Nd, Gd and Dy) binary system at 1073K under the Cu-rich side of the correlation coefficient and electric arc furnace cast . The experiments prove that the compounds of the Cu-rich side of the Cu-Y and Cu-Dy binary system the phase Cu7RE, in the Cu-Nd and Cu-Gd binary system Cu-rich side compound Cu6RE phase. The only Cu7Dy above 1073K stable at low temperature experience the eutectoid into FCC (Cu) Cu5Dy_L. (2) to the experimental results and literature information, a reasonable choice of thermodynamic model, the use of the CALPHAD technical evaluation and optimization of the Al-Yb, Cu-Gd, Cu-Dy, Cu-Er and Sb-Y four binary system, all calculations The correlation coefficient and thermodynamic properties of the experimental data. (3) XRD, SEM / EDX technique accurate determination of the partial correlation coefficient of the Al-Cu-Nd ternary 673K. The experiments confirmed that six ternary phase: τ1-Al8Cu4Nd, T2 is Al9Cu8Nd2, of ortho-Al6Cu7Nd, T4-Al2.4Cu8.6Nd, T5-Al3CuNd and τ6-AlCuNd 673K. The experimental results and literature information, the thermodynamic optimization of the Al-Cu-Nd system, a reasonable description of each phase Gibbs free energy of the thermodynamic parameters. (4) by means of X-Ray diffraction analysis techniques Determination of ternary Al-rich corner of the Al-Cu-Er partial correlation coefficient at 673K. The experiments confirmed the presence of ternary compound (τ1-Al8Cu4Er), and confirmed the Al-rich corner of the three-phase regions, as well as a two-phase region. The experimental results and literature information, thermodynamic optimization of the Al-Cu-Er system, a reasonable description of each phase Gibbs free energy of the thermodynamic parameters. (5) select reasonably self-consistent thermodynamic database of the binary system, combined with the the ternary experimental information and a reasonable choice of thermodynamic model, the use of the CALPHAD technical evaluation and optimization of the Al-Cu-Y, Al-Cu-Gd, Al-Cu -Dy, Al-Cu-Yb, Al-Cu-Ti and Al-Sb-Y five ternary system, the initial construction of the Al-Cu-Y-Nd-Gd-Dy-Er-Yb-Sb-Ti system thermodynamic database. Reaction liquid zero variable calculated by the database, the isothermal section of the vertical section and thermodynamic properties and experimental data consistent. (6) by means of metallography, scanning electron microscopy and X-ray diffraction analysis and other means of detection and analysis, and determination of the Al-Cu-RE (RE = Y, Nd, Gd, Dy and Ti) ternary electric arc furnace casting state. Optimized obtain thermodynamic database to simulate the the ternary equilibrium solidification process and the non-equilibrium solidification process. The simulation results are reasonable interpretation of the experimentally obtained ternary alloy microstructure. (7) the use of the thermodynamic database, the Al-Cu-Y, Al-Cu-Nd, Al-Cu-Gd, Al-Cu-Dy, Al-Cu-Er, Al-Cu-Yb and Al-Cu-Ti glass forming ability crystalline phase relationship between the driving force. The study showed that the Al-Cu-Y, Al-Cu-Nd and Al-Cu-Ti ternary amorphous formation region and to each crystal phase driving force in the supercooled liquid, wherein the driving force of the alloy forming the amorphous ability. Prediction system, Al-Cu-Y, Al-Cu-Nd, Al-Cu-Gd, Al-Cu-Dy, Al-Cu-Er, Al-Cu-Yb and Al-Cu-Ti alloy according to this criterion, glass-forming ability. And further calculated the constant driving force of these systems line, where you can get easy to form amorphous alloy composition area. The calculation of the above system, and only through the amorphous alloy, an Al-Cu-Yb prepared get Al3RE reinforced heat-resistant aluminum alloy, very close to the calculated composition range Patent reported.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Aluminum
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