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Title: Effects of in-process cryocooling on metallurgical and mechanical properties of friction stir processed Al7075 alloy
Authors: Kumar A.
Godasu A.K.
Pal, Kaushik
Mula, Suhrit
Published in: Materials Characterization
Abstract: Friction stir processing (FSP) of heat treatable aluminum alloys is reported to deteriorate strength and hardness properties in spite of huge grain size refinement. The improvement in strength due to the grain size refinement after FSP could not be able to offset the reduction in strength due to coarsening or dissolution of the strengthening precipitate(s). To overcome this, the present work investigates an effective way of heat rejection from the FSP zone to control the precipitate evolution besides the grain size refinement during FSP of Al7075 alloy. The FSP was carried out with standardized process parameters (i.e. 720 rpm, 65 mm/min traverse speed) under two different cooling environments: (i) at normal air cooling and (ii) by rushing a chilled mixture (−30 °C) of liquid nitrogen and methanol through the bottom of the backing plate. Microstructural evolution was examined through optical, scanning and transmission electron microscopy and electron backscatter diffraction to confirm the grain size and morphology of precipitate(s) formed. The in-process cryocooling during the FSP led to 65 and 72% improvement in the Vickers hardness and tensile strength, respectively, in comparison to the solutionized base metal. The results have been analyzed in terms of precipitate interface characteristics and its strengthening effect, Hall–Petch strengthening due to grain size reduction and tradeoff between them. © 2018 Elsevier Inc.
Citation: Materials Characterization (2018), 144(): 440-447
Issue Date: 2018
Publisher: Elsevier Inc.
Keywords: Age-hardenable alloy
Electron microscopy
In-process cryocooling
Mechanical characterization
ISSN: 10445803
Author Scopus IDs: 55716701800
Author Affiliations: Kumar, A., Department of Metallurgical and Materials Engineering, IIT Roorkee247667, India
Godasu, A.K., Department of Metallurgical and Materials Engineering, IIT Roorkee247667, India
Pal, K., Department of Mechanical and Industrial Engineering, IIT Roorkee247667, India
Mula, S., Department of Metallurgical and Materials Engineering, IIT Roorkee247667, India
Corresponding Author: Mula, S.; Department of Metallurgical and Materials Engineering, IIT RoorkeeIndia; email:
Appears in Collections:Journal Publications [ME]
Journal Publications [MT]

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