Some Observations on Microstructural Changes in a Mg-Based AE42 Alloy Subjected to Friction Stir Processing |
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Authors: | Harpreet Singh Arora Harpreet Singh B K Dhindaw |
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Affiliation: | (1) School of Mechanical, Material and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab, 140001, India |
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Abstract: | The main aim of the current study is the analysis of friction stir processing (FSP) of Mg-based alloys as a possible tool
for nanocomposites production. The study reports microstructural changes taking place in a Mg-based alloy (AE42) subjected
to FSP under different cooling conditions. The FSP process was carried out with single as well as multipass options. The friction
stir processed samples were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission
electron microscopy (TEM), focused ion beam (FIB)-scanning ion microscopy (SIM), and X-ray diffraction (XRD). It was observed
that FSP tends to fragment the elongated precipitates and produces near homogeneous distribution of fine particles. The smallest
particle size was observed to be produced by double-pass FSP supplemented by rapid cooling, thereby generating in situ nanocomposites. Vickers microhardness testing was done along the thickness (transverse direction) of the specimen to study
and understand the variation of hardness with thickness. Nearly a two-times increase in the microhardness of AE42 was observed
in the case of double-pass, FSP AE42 with cooling at temperature of approximately 253 K (–20 °C). To confirm these observations,
another magnesium alloy AM50 was also friction stir processed under similar conditions. The fine submicron grain structure
produced in AE42 alloy contributed immensely toward grain boundary strengthening and Orowan strengthening had only marginal
influence. Subgrain boundary pinning by in situ nanoparticles contributed significantly in the strengthening process. |
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