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Effect of Rare Earth Elements and Solidification Rate on the Microstructure and Phase Composition of AZ31-RE-Sb

Author: WuXiaoChao
Tutor: LiQingKui
School: Zhengzhou University
Course: Materials Processing Engineering
Keywords: AZ31 magnesium alloy Rare earth alloying Solidification rate Organizational structure Solvent extraction
CLC: TG111.4
Type: Master's thesis
Year: 2010
Downloads: 72
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Abstract


The rare earth alloying is an effective means of improving the performance of magnesium alloy. The the coarse acicular rare earth phase formed in the aluminum-magnesium alloy containing alloy matrix generate strong fragmented, and cause stress concentration, and seriously affect the strength and toughness of the alloy and further improve plasticity. In this paper, AZ31 wrought magnesium alloy based study and compared by means of analysis and testing of the OM, XRD, SEM EDS, DTA, cerium-rich mixed rare earth and pure cerium alloy organizational structure. Especially in our group on the basis of the magnesium alloy rare earth phase ball, AZ31-MM and AZ31-Ce alloy by Sb exhibit different behavior in the process of rare earth phase ball; through the use of ordinary solidification process, rapid solidification process and rapid solidification prepared alloy, the solidification rate of the alloy organizational structure to by DTA analysis of the solidification process to explore the mechanism of rare earth phase ball. Finally, the study of the of AZ31 1? 1% Sb alloy second phase in the solvent extraction method and process, and the product is extracted for further analysis. Further improve the plastic processing performance and use of performance provides a theoretical reference for rare earth alloy AZ31 magnesium alloy control and improvement of the organizational structure. The results show that the rich cerium mixed rare earth and pure cerium has a different impact on the organization of the AZ31 magnesium alloy. AZ31 magnesium alloy rare earth alloying pure Ce alloy phase composed of α-Mg, β-Mg17Al12 and Al11Ce3 richer cerium mixed rare earth alloy grain finer, β-Mg17Al12 phase is more diffuse, needle-like matrix phase less. DTA analysis shows that each phase of the AZ31 alloy precipitation sequence: The respective phases of α-of Mg → β-of Mg17Al12; of AZ31-Ce Alloy precipitation sequence: Al11Ce3 → α-Mg → β-Mg17Al12; AZ31-Ce-Sb alloy phase precipitation sequence CeSb → Al11Ce3 → α-Mg → β-Mg17Al12. The composite alloying MM-Sb and Ce-Sb composite alloying can be more diffuse spherical second phase, and the level of detail of the MM-Sb alloy. Solidification rate of AZ31 1? 1% Sb alloy composition and solidification process have a great impact. The results show that: the rapid solidification speed range, with the gradual increase in the solidification rate, the second phase in the alloy step-by-step refinement spheroidization, diffusion, Φ2mm size of the sample has the best organization, its organization dispersed the spherical phase of Al-Ce-Sb ternary phase; rapid solidification velocity range, as the solidification rate increases, a second phase in the alloy is gradually distributed in the matrix into vermicular worm-like compared with alkylene rapid solidified alloy structure of the spherical phase, Sb content is reduced, the Al content increased. DTA curve analysis, rapid solidified and rapid solidification state than ordinary solidified eutectic temperature, rapid solidified alloy spherical Al-Ce-Sb ternary phase precipitation temperature of 630.03 ° C; rapid solidification wormlike alloys Al-Ce-Sb ternary phase precipitation temperature to 628.61 ° C Of AZ31 1? 1% Sb alloy second phase solvent extraction test study reached the optimum extraction solution: VHCl: VH2O = 1:1 concentration of aqueous hydrochloric acid. By XRD analysis identified The extraction product phase composition: of Mg17Al12, Sb, AlSb, CeSb and Al4Ce; drawn by SEM EDS analysis of the extracted product, the elemental Sb irregular polyhedron, AlSb phase was irregular polyhedron spherical CeSb irregular polyhedron shape evolution.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Physics of metals > The liquid structure of the metal and solidification theory
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