Improvement of the mechanical properties of aluminium alloy (AA2219) with large plastic deformation at ambient and cryogenic temperatures

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dc.contributor.advisor Mukhopadhyay, Jyoti
dc.contributor.author Davinder
dc.date.accessioned 2017-10-18T05:35:12Z
dc.date.available 2017-10-18T05:35:12Z
dc.date.issued 2017
dc.identifier.citation Davinder (2017). Improvement of the mechanical properties of aluminium alloy (AA2219) with large plastic deformation at ambient and cryogenic temperatures (M.Tech. Dissertation). Indian Institute of Technology, Gandhinagar, pp. 99 (Acc No: T00251) en_US
dc.identifier.uri https://repository.iitgn.ac.in/handle/123456789/3231
dc.description.abstract Aluminum alloys find the extensive applications in aerospace industry due to their light weight, and combination of other mechanical properties such as high strength, toughness, good weldability etc. AA 2219 alloy is used for the fabrication of propellant tanks of cryogenic stages. In the present study thermomechanical processing is used to improve the mechanical properties of AA 2219. In the present study, we critically evaluate the role of cryorolling and present for the first time, mechanical properties of AA 2219 large strain deformed sheets and bars at 77K (-1960C). In the first part of the present work Aluminum alloy AA 2219 bars were cryorolled to three different reduction ratios viz. 30pct, 50pct and 70pct in a caliber rolling mill. Mechanical properties of the rolled bars were evaluated at ambient temperature and 77K in as-rolled condition as well as after peak aging. The mechanical properties monotonically increased with increase of the percentage of reduction in both as received and aged condition. Bars with excellent combination of strength and ductility could be fabricated using cryorolling and the mechanical properties obtained were correlated to microstructural evolution through both optical and transmission electron microscopy. An improvement in the mechanical properties has been observed after aging for 8hours for all three cryorolled bars. For ST + 70% CR bar UTS of 523 MPa, 0.2 % YS of 451 MPa and the percentage elongation of 15 % have been reported at room temperature. Significant improvement in the mechanical properties of the cryorolled bars was motivation for the second part of the present work. Aluminum alloy AA 2219 sheets are required for the fabrication of propellant tanks. The fabrication involves roll bending of sheets to shells and long seam welding of shells. These shells are welded to end domes to realize propellant tanks. The higher surface area of the sheets poses difficulty in maintaining work piece temperature during cryorolling. In the second part, sheets were produced by rolling at room and cryogenic temperatures. Accordingly, AA 2219 plates were rolled to same amount of deformation (86.6%) in three pre-deformation conditions. Viz. (a) without solution treated (WST) (b) solution treated and reverse rolled at room temperature (ST & RR @ RT) (c) solution treated and reverse rolled at cryogenic temperature (ST & RR @ CT) The mechanical properties of sheets in as rolled and peak aged condition were evaluated at RT and 77K and the same was correlated to the microstructural evolution using both optical and transmission electron microscopy. The sheets rolled without solution treatment exhibited mechanical properties that were inferior to the starting material. On the other hand, the sheets rolled after solution treatment at both room and cryogenic temperature showed significant improvement in mechanical properties. An important outcome of this study is to show that cryorolling is not essential for obtaining improved mechanical properties, as similar properties could be obtained by room temperature rolling under identical conditions. Mechanical properties were also evaluated at 77K for sheets and similar improvement was also observed for sheet rolled at room and cryogenic temperature in both as-rolled and aged condition. Based on this study it is recommended to process AA2219 sheets to a true strain of 2 at RT to impart improved mechanical properties (490 MPa yield strength at RT and 627 MPa at 77K). en_US
dc.description.statementofresponsibility by Davinder
dc.format.extent 99 p.; 29 cm.
dc.language.iso en_US en_US
dc.publisher Indian Institute of Technology Gandhinagar en_US
dc.title Improvement of the mechanical properties of aluminium alloy (AA2219) with large plastic deformation at ambient and cryogenic temperatures en_US
dc.type Thesis en_US
dc.contributor.department Mechanical Engineering
dc.description.degree M.Tech.


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