Tensile Properties of a Heat-Resistant Aluminium Alloy Strengthened by T-Al 6 Mg 11 Zn 11 Intermetallic Phase
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.107
Tensile Properties of a Heat-Resistant Aluminium Alloy Strengthened by T-Al6Mg11Zn11 Intermetallic Phase Satoshi Nakatsuka1, Masato Ishihara1, Naoki Takata1, Asuka Suzuki1 and Makoto Kobashi1 1 Department of Materials Process Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
ABSTRACT We have examined tensile properties of a novel heat-resistant aluminium (Al)-based alloy (with a composition of Al-5Mg-3.5Zn (at%)) strengthened by the T-Al6Mg11Zn11 (cubic) intermetallic phase at various temperatures. The tested specimens of the present alloy were solution-treated at 450oC for 24 h and subsequently aged at 200 or 300 oC for 1 h. The granular precipitates of the T phase were dispersed rather homogenously in the grain interior in the specimen aged at 300°C. In the specimen aged at 200°C, numerous fine precipitates with a mean size of ~20 nm were observed in the -Al matrix. The specimen pre-aged at 200°C for 1 h exhibited a superior strength to the conventional Al alloys at elevated temperatures ranging from 150 to 200°C (corresponding to service temperatures for compressor impellers in turbochargers).
INTRODUCTION Wrought aluminium (Al) alloys are the most common materials used for radial compressor impellers in vehicle turbochargers because of their relatively specific high strength, resulting in a low compressor wheel inertia [1, 2]. The turbocharger is being used to improve the overall efficiency of the combustion process in current diesel engine [1]. Their compression ratio is limited by the strength and fatigue resistance of the applied Al alloys at elevated temperatures. One of the most common wrought Al alloys used for radial impellers is alloy 2618. However, the strength of the alloy 2618 is significantly reduced at temperatures above 200°C [3], resulting in the limited service temperature of compressor impellers for turbochargers. Thus, further demands for improving the combustion efficiency make it necessary to increase the service temperature of the Al alloys used for this application.
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One of promising routes to improve the high-temperature strength is to introduce stable intermetallic phases with high volume fractions in the metal matrix [4,5]. Thus, fabricating the -Al (fcc) matrix strengthened by intermetallic phase could potentially improve their high-temperature properties for their use in compressor impellers [6]. In order to achieve high volume fractions of precipitates (intermetallic phase for strengthening) in Al-Al matrix is required at elevated temperatures (corresponding to the solution-treatment temperature). The Al–Mg–Zn ternary phase diagram [7] presents a ternary intermetallic compound of T-Al6Mg11Zn11 phase (cubic s
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