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Research Papers

The Effect of Applied Forging Pressure on Primary Structure Deformation in Rheology Forging Process With Solid Fraction Controlled A356 and AA2024 Alloys

[+] Author and Article Information
S. M. Lee

Engineering Research Center for Net Shape and Die Manufacturing, Pusan National University, San 30, Chang-Jun Dong, Busan 609-735, South Koreasmlee@pusan.ac.kr

H. H. Kim

Graduate School of Mechanical and Precision Engineering, Pusan National University, San 30, Chang-Jun Dong, Busan 609-735, South Koreagn777me@pusan.ac.kr

C. G. Kang

School of Mechanical Engineering, Thixo-Rheo National Research Laboratory, Pusan National University, San 30, Chang-Jun Dong, Busan 609-735, South Koreacgkang@pusan.ac.kr

J. Eng. Mater. Technol 132(2), 021015 (Mar 12, 2010) (7 pages) doi:10.1115/1.4000671 History: Received August 01, 2008; Revised February 02, 2009; Published March 12, 2010; Online March 12, 2010

Mechanical properties and microstructure of heat-treated samples of A356 and AA2024 aluminum alloys, which were rheoforged by varying the change in pressure and temperature were investigated, preventing defects such as porosity, liquid segregation, and insufficient filling occurring during rheoforging process. The rheology material was fabricated by an electromagnetic stirring process by controlling stirring current so that shearing force and temperature of the molten metal were controlled during electromagnetic stirring. As a result, by crushing dendrite and rosette type microstructures, fine and globularized rheology material was obtained and the feasibility of the rheoforging process was found to be positive. In the case of the direct rheoforging process, excessive applied forging-pressure caused material spattering, which in turn caused eutectic segregation. This segregation brought about a shrink hole and thus led to a deterioration of mechanical strength. According to varied applied forging pressures, agglomeration phenomena of primary particles of wrought aluminum alloy remarkably increased as compared with an as-cast aluminum alloy.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic diagram of electromagnetic stirrer in an inner diameter of 165 mm and a height of 300 mm and the crucible in an inner diameter of 90 mm and height of 183 mm

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Figure 2

Schematic diagrams of rheology forging process

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Figure 3

Microstructures after electromagnetic stirring at the center position with A356 alloy according to pouring temperature (ts=60 s, C=80 A)

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Figure 4

Microstructures after electromagnetic stirring at the center position with A356 according to stirring current (Tp=655°C, ts=60 s)

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Figure 5

Microstructures after electromagnetic stirring according to pouring temperature at center position with AA 2024 (ts=60 s, C=60 A)

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Figure 6

Microstructures after electromagnetic stirring according to stirring current at the center position with AA 2024 (Tp=690°C, ts=60 s)

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Figure 7

Positions of microstructure and tensile specimen

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Figure 8

Microstructures of A356 forged sample versus various forging-pressure at position 1 (stirring current is 60 A and solid fraction is 70%)

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Figure 9

Microstructures of forged A356 sample versus various forging-pressure at position 2 (stirring current is 60 A and solid fraction is 70%)

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Figure 10

Mechanical properties of A356 rheoforged sample

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Figure 11

Microstructures of A356 alloy sample fabricated at condition 4 in Table 2 (sample with spattered melt at the parting line)

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Figure 12

Microstructure of AA2024 forged sample versus various forging-pressure at position 1 (stirring current is 60 A and solid fraction is 70%)

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Figure 13

Microstructures of AA2024 forged sample versus various forging-pressure at position 2 (stirring current is 60 A and solid fraction is 70%)

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Figure 14

Mechanical properties of AA2024 rheoforged sample

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Figure 15

Photograph and EDS analysis of air-blow in AA2024 rheoforged sample

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