Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1574619 | Materials Science and Engineering: A | 2015 | 12 Pages |
Abstract
Submerged friction-stir processing under cryogenic conditions was employed to fabricate ultrafine-grained nanocomposites with enhanced mechanical characteristics. Al-Mg alloy sheet with 3 vol% TiO2 nanoparticles were processed under air (ambient temperature), a water-dry ice medium (~â25 °C), and liquid nitrogen. It is shown that a homogenous distribution of reinforcement particles throughout the metal matrix is attained at a rotational speed of 1400 rpm and a traverse velocity of 50 mm/min after 4 passes. In situ formation of Al3Ti and MgO nanophases during multi-pass processing is shown by transmission electron microscopy. Under the cryogenic cooling condition, ultrafine grains and cellular structures with sizes smaller than 1 μm and 200 nm are attained. It is shown that the formation of an ultrafine-grained structure is accompanied with significant improvement (150-200%) in the mechanical strength. The tensile yield strength of ~170 MPa, elongation of ~22% and Vickers hardness of ~165 HV are attained. A change in the fracture mode from ductile-brittle to fully ductile is presented when the cryogenic processing is employed. A relationship between the grain size and the fracture features is demonstrated. Effects of cooling conditions on the microstructure and mechanical properties of friction stir processed Al-based nanocomposites are addressed.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
F. Khodabakhshi, A.P. Gerlich, A. Simchi, A.H. Kokabi,