Effect of Mg17Al12 precipitates on the microstructural changes and mechanical properties of hot compressed AZ91 magnesium alloy |
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Authors: | SW Xu N Matsumoto S Kamado T Honma Y Kojima |
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Affiliation: | aDepartment of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka-machi, Nagaoka, Niigata 940-2188, Japan |
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Abstract: | During hot compression, Mg17Al12 (β) precipitates show strong influence on the microstructural changes of 415 °C-24 h homogenized AZ91 alloy. When compressed at 300 °C and 350 °C, dynamic recrystallization (DRX) only occurs near grain boundaries with discontinuous β precipitate pinning at the newly DRXed grain boundaries. With increasing compression temperature and decreasing strain rate, the β-precipitating region expands; however, the amount of pinning precipitates decreases, resulting in increases in the DRX ratio and average DRXed grain size. With a compression ratio of only 50%, the specimen compressed at 350 °C and a strain rate of 0.2 s−1 (designated 350 °C-0.2 s−1 compressed specimen) shows an ultimate tensile strength (UTS) of 334 MPa, a 0.2% proof stress (PS) of 195 MPa and an enough elongation of 17.9%. After a subsequent aging treatment at 180 °C, due to the large number of β precipitates, the strength of the compressed specimens are further improved, and the specimen peak aged after compression at 400 °C and 0.2 s−1 shows UTS of 364 MPa and PS of 248 MPa with a moderate elongation of 7.7%. |
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Keywords: | AZ91 magnesium alloy Hot compression Precipitates Microstructure Mechanical property |
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