Characterization and analysis of low-temperature superplasticity in 8090 Al-Li alloys
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Characterization and Analysis of Low-Temperature Superplasticity in 8090 AI-Li Alloys H.P. PU, F.C. LIU, and J.C. H U A N G The 8090 A1-Li alloys, after a special thermomechanical process (TMP), exhibited low-temperature superplasticity (LTSP) from 350 ~ to 450 ~ and behaved differently from the conventional high-temperature superplasticity (HTSP). The LTSP sheets after - 7 0 0 pct elongation at 350 ~ and 8 x l 0 -4 s -1 still possessed fine "(sub)grains" 3.7 /xm in size and narrow surface Lidepletion zones 11 /xm in width, resulting in a post-SP T6 strength of - 5 0 0 MPa, significantly higher than that of the 8090 alloys tested at normal superplastic temperature of 525 ~ or above. Examination from the movement of surface marker lines in LTSP samples confirmed the role of grain boundary sliding (GBS), coupled with grain rotation and migration. During the initial stage (
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