Characterization of spalled AZ31B processed by ECAE

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

卷:767

Article

Krywopusk, Nicholas M.^1,2  Williams, Cyril L.^2,3  Kecskes, Laszlo J.^2,4  Weihs, Timothy P.^1,2 

[1] Johns Hopkins Univ, Dept Mat Sci & Engn, 3400 North Charles St, Baltimore, MD 21218 USA

[2] Johns Hopkins Univ, Johns Hopkins Extreme Mat Inst, 3400 North Charles St, Baltimore, MD 21218 USA

[3] US Army, Protect Div, Weap & Mat Res Directorate, Res Lab, Aberdeen Proving Ground, MD 21005 USA

[4] US Army, Mat & Mfg Sci Div, Weap & Mat Res Directorate, Res Lab, Aberdeen Proving Ground, MD 21005 USA

关键词: Characterization;    Magnesium alloys;    Equal channel angular;    Extrusion;    Voids;    Twinning;   

DOI  :  10.1016/j.msea.2019.138298

来源: Elsevier

【 摘 要 】

Spall recovery experiments were performed on ECAE processed AZ31B 4B(C) sample plates at approximately 200 and 400 m/s impact velocities corresponding to approximately 0.8 and 1.7 GPa shock stresses respectively, with plate normals parallel to the Extrusion and Transverse directions. The primary failure mechanisms were investigated through a combination of fractography and Electron Backscatter Diffraction (EBSD). It was found that the existence of clusters of large, elongated Mn-Al particles in the alloy played a critical role in the onset and early development of spall failure. The elongated particles that were fractured during processing were the nucleation sites for voids, which then grew by crack propagation through the precipitates during shock. Void growth was found to transition to a more ductile mode in later stages of growth, and differences in later void growth between the two orientations were observed in the fracture surfaces. In the Extrusion direction sample, well-developed voids display fracture surfaces with a large number of nanovoids containing no nanoprecipitates. In contrast, voids in the Transverse direction sample displayed larger, sub-micrometer voids that intermittently contained precipitates. Extension twinning was also observed to play a role in void growth at the later stages, with the twin area fraction increasing significantly near developed voids. In the Extrusion sample shock compressed to 1.73 GPa, a series of twins and elongated grains were observed, and it is hypothesized that they aid in the formation of cracks between the voids.

【 授权许可】

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