Research Papers

Manufacturing of Nanostructured Blades for a Francis Turbine by Isothermal Forging of AA6063

[+] Author and Article Information
C. J. Luis

e-mail: cluis.perez@unavarra.es

R. Luri

Mechanical, Energetics and Materials Engineering Department,
Public University of Navarre,
Campus de Arrosadia s/n,
Pamplona 31006, Navarre, Spain

Manuscript received January 8, 2013; final manuscript received August 9, 2013; published online November 5, 2013. Assoc. Editor: Brad L. Kinsey.

J. Manuf. Sci. Eng 136(1), 011009 (Nov 05, 2013) (11 pages) Paper No: MANU-13-1007; doi: 10.1115/1.4025396 History: Received January 08, 2013; Revised August 09, 2013

This research work deals with the manufacturing of blades for a Francis turbine with a submicrometric structure through the isothermal forging of a heat-treatable aluminum alloy that has been previously processed by angular channel extrusion. In addition, mechanical properties and microstructure of these same blades are analyzed. A comparative study is also carried out between the properties obtained in the forged blades from the alloy previously deformed through angular channel extrusion and those obtained by employing two other isothermal forging processes of this alloy which mean utilizing different process stages. Moreover, a modeling by finite element about the isothermal forging process of the blades is performed using flow rules obtained from compression tests on these alloys at different temperatures. In this way, a much higher degree of accuracy is achieved in the results compared with that obtained through traditional approaches. With this present study, it is intended to make some progress in the development of nanostructured mechanical components with the aim of demonstrating the feasibility of their manufacturing and achieving an improvement in their mechanical properties.

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Fig. 1

Hydraulic press of 3000 kN adapted for isothermal forging (a) and dies for the forging of the blades for a Francis turbine (b)

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Fig. 2

ECAE press (a) and dies (b) used for the angular channel extrusion of AA6063

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Fig. 3

Preform (a) and forged part (b) of AA6063

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Fig. 4

Blades of AA6063 manufactured from starting material coming from the three studied cases and starting preform

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Fig. 5

Employed geometries in the simulations

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Fig. 6

Flow curves of AA6063

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Fig. 7

Plastic strain for the case at 150 °C: (a) stroke at 5 mm, (b) stroke at 7 mm, (c) stroke at 9 mm, (d) stroke at 11 mm, and (e) stroke at 12.5 mm

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Fig. 8

Temperature field inside the billet for isothermal forging at 150 °C: (a) stroke at 5 mm, (b) stroke at 9 mm, and (c) stroke at 12.5 mm

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Fig. 9

Accumulated damage in the part for the case of 150 °C: (a) stroke at 5 mm, (b) stroke at 7 mm, (c) stroke at 9 mm, (d) stroke at 11 mm, and (e) stroke at 12.5 mm

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Fig. 10

Stress values in the die for the case at room temperature: (a) upper die: stroke at 5 mm, (b) upper die: stroke at 12.5 mm, (c) lower die: stroke at 5 mm, and (d) lower die: stroke at 12.5 mm

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Fig. 11

Comparison between experimental values of the force developed by the press at temperature values of 25 °C (a) and 150 °C (b) and the finite element simulations using different friction coefficient values

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Fig. 12

Comparison of mean microhardness values for AA6063 blades for the three cases considered. The uncertainty values are one standard deviation

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Fig. 13

Comparative analysis among the experimental values for the force developed by the press in the three cases under consideration: (a) temperature at 25 °C, (b) temperature at 150 °C, and (c) temperature at 250 °C

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Fig. 14

Microstructure (SEM micrographs) of the blades manufactured by the isothermal forging of the AA6063 previously ECAE processed and after the aging heat treatment: (a) starting material (N0), (b) after ECAE (N2), (c) forging at 25 °C, (d) forging at 150 °C, and (e) forging at 250 °C

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Fig. 15

Pump design manufactured utilizing the nanostructured blades




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