期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2016.12.020
关键词
Al-Ge-Si; Bauschinger effect; Precipitate; Orowan bypass; Super-Dislocation model
类别
资金
- U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division [DE-SC0012483, DE-SC0012587]
- U.S. Steel
- U.S. Department of Energy (DOE) [DE-SC0012483] Funding Source: U.S. Department of Energy (DOE)
Wrought Al-Ge-Si alloys were designed and produced to ensure dislocation bypass strengthening (hard pin precipitates) without significant precipitate cutting/shearing (soft pin precipitates). These unusual alloys were processed from the melt, solution heat treated and aged. Aging curves at temperatures of 120, 160, 200 and 240 degrees C were established and the corresponding precipitate spacings, sizes, and morphologies were measured using TEM. The role of non-shearable precipitates in determining the magnitude of Bauschinger was revealed using large-strain compression/tension tests. The effect of precipitates on the Bauschinger response was stronger than that of grain boundaries, even for these dilute alloys. The Bauschinger effect increases dramatically from the under-aged to the peak aged condition and remains constant or decreases slowly through over-aging. This is consistent with reported behavior for Al-Cu alloys (maximum effect at peak aging) and for other Al alloys (increasing through over-aging) such as Al-Cu-Li, Al 6111, Al 2524, and Al 6013. The Al-Ge-Si alloy response was simulated with three microstructural models, including a novel SD (SuperDislocation) model, to reveal the origins of the Bauschinger effect in dilute precipitation-hardened / bypass alloys. The dominant mechanism is related to the elastic interaction of polarized dislocation arrays (generalized pile-up or bow-out model) at precipitate obstacles. Such effects are ignored in continuum and crystal plasticity models.
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