Internal friction and microplastic deformation behavior of pure magnesium processed by equal channel angular pressing

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

卷:561

Article

Fan, G. D.¹  Zheng, M. Y.¹  Hu, X. S.¹  Wu, K.¹  Gan, W. M.²  Brokmeier, H. G.^2,3 

[1] Harbin Inst Technol, Sch Mat Sci & Engn, Harbin 150001, Peoples R China

[2] Helmholtz Zentrum Geesthacht, Inst Mat Res, D-85748 Garching, Germany

[3] Tech Univ Clausthal, Inst Mat Sci & Engn, D-38678 Clausthal Zellerfeld, Germany

关键词: Magnesium;    ECAP;    Cyclic loading;    Internal friction;    Microplasticity;    Texture;   

DOI  :  10.1016/j.msea.2012.10.083

来源: Elsevier

【 摘 要 】

Equal channel angular pressing (ECAP) was performed on the as-extruded commercial pure magnesium at 250 degrees C for 4 passes. The internal friction of the ECAPed pure Mg as a function of strain amplitude was investigated by dynamic mechanical analyzer (DMA), and the cyclic microplasticity of pure Mg was investigated by tensile loading and unloading test. After ECAP processing, the grain size is significantly refined, the texture component with basal planes parallel to extrusion direction is replaced by a new stronger one with basal planes having a tilting angle of about 40 to the extrusion direction. The stress in microplastic region is reduced with increasing ECAP passes, while the internal friction increases. The internal friction of Mg at high strain amplitude is closely related to microplastic deformation and can be interpreted by dislocation mechanism. The Granato and Lucke model only satisfies in anelastic regions, while the internal friction in microplastic deformation region should be explained in terms of the internal friction model postulated by Peguin. The internal friction related to microplasticity can be divided into two parts with different activation volumes of dislocation motion, which correspond to the two regions of microplasctic deformation process. The initial stage associated with dislocation motion on basal plane shows larger activation volume and lower friction stress of dislocations. The second stage related to the annihilation and tangle of dislocations is characterized by larger hardening exponent and friction stress. (C) 2012 Elsevier B.V. All rights reserved.

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