Mechanism of the Bauschinger effect in Al-Ge-Si alloys

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:684

Article

Gan, Wei¹  Bong, Hyuk Jong²  Lim, Hojun³  Boger, R. K.⁴  Barlat, F.⁵  Wagoner, R. H.² 

[1] Medtronic, Mounds View, MN 55112 USA

[2] Ohio State Univ, Dept Mat Sci & Engn, Columbus, OH 43210 USA

[3] Dept Computat Mat & Data Sci, Sandia Natl Labs, Albuquerque, NM 87185 USA

[4] Dassault Syst, Mason, OH 45040 USA

[5] Pohang Univ Sci & Technol, GIFT, Pohang 37673, Gyeongbuk, South Korea

关键词: Al-Ge-Si;    Bauschinger effect;    Precipitate;    Orowan bypass;    Super-Dislocation model;   

DOI  :  10.1016/j.msea.2016.12.020

来源: Elsevier

【 摘 要 】

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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