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1、ELSEVIER Press ScienceDirectTransactions of Nonferrous Metals Society of ChinaAvailable onli ne at Trans. Nonferrous Met. Soc. China 22(2012) 1866-1871Formation of precipitates and recrystallization resistance in Al-Sc-Zr alloysJIA Zhi-hong1*2, Jostein R0YSET3, Jan Ketil SOLBERG2, LIU Qing11. School
2、 of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;2. Department of Materials Science and Engineering,Norwegian University of Science and Technology, NO-7491, Trondheim, Norway;3. Hydro Aluminium Research and Technology Development, N0-6600, Sunndalsora, NorwayRecei
3、ved 10 November 2011; accepted 20 June 2012Abstract: AI-x%Sc-0.11 %Zr alloys (x=0, 0.02, 0.05, 0.08, 0.11, 0.15) were produced by a chill cast procedure. The effect of Sc content on the precipitation of Ab(Sc,Zr) during heat treatment at 475 C for 12 h was studied Nucleation, precipitation and distr
4、ibution of Al3(Sc,Zr) precipitates were found to be strongly related to the Sc content. With increasing the Sc content, the average radius of the precipitates decreases, while the number density of the precipitates increases, as investigated by transmission electron microscopy (TEM). The distributio
5、n of the precipitates becomes more and more homogeneous when the Sc content is increased. The recrystallization resistance of samples that was 90% cold rolled and isothermal annealed for half an hour in the temperature range of 200600 C was investigated. The results show that the recrystallization t
6、emperature varies from 250 C for the alloy without Sc to about 600 C for the alloy containing 0.15% Sc because of the high density of Al3(Sc,Zr) precipitates.Key words: aluminium alloy; precipitate; recrystallization resistance1 IntroductionA tremendous amount of research has been canied out on Sc-c
7、ontaining Al alloys over the last 20 years, owing to the improved properties that can be obtained by a Sc addition 1-8 One of the most important advantages is related to the formation of a dense and homogeneous distribution of precipitates during thermomechanical processing at elevated temperatures,
8、 which in turn leads to an efficient control of the microstructure of the alloy 9JO. The precipitates are of the AI3SC phase, which is the equilibrium phase of the Al-Sc phase diagram 1 It is well known that adding Sc in combination with Zr leads to a higher temperature stability of the precipitates
9、 (slower rate of coarsening) as compared with a Sc addition alone The Al3Sc phase can dissolve a considerable amount of Zr when Sc and Zr are added in combination. The precipitates are frequently denoted as Al;(Sci-xZrx). It has been discovered that, due to the faster diffusion rate of Sc as compare
10、d with Zr, the formation of these precipitates starts with almost pure A13Sc whereas the Zr content gradually increases during growth of the precipitates, leading to a corc/shell structure of the precipitates 11-13.The high price of Sc is prohibitive for extended commercial applications of Sc-contai
11、ning aluminium alloys. At present, the use is limited to high-end sporting equipment and to a few aerospace applications. In order to draw the benefit of Sc addition in other product ranges, it is necessary to minimize the associated cost by establishing the minimum Sc content necessary for obtainin
12、g the desired effect The aim of the present investigation is to determine the minimum Sc content needed for achieving a dense and homogeneous distribution of ASci-xZrJ precipitates in an Al-Sc-Zr alloy.2 Experimental2.1 Material preparationSix Al-Sc-Zr alloys with different Sc contents were prepared
13、 Fe and Si are inevitable impurities in commercial Al alloys, and one therefore chose aluminium-based metal with a small content of Fe and Si for producing these alloys Sc and Zr were added asFoundation item: Project (CDJZR12130048) supported by the Fundamental Research Funds for the Central Universities of China; Project supported by the Research Council of NorwayCorresponding author: JIAZhi-hong; Tel: +8623*65102029; E-mail: zhihongjiaDOI: 10.10161003-6326(11)6I399-X