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Research Papers

Experimental Analysis and Microstructure Modeling of Friction Stir Extrusion of Magnesium Chips

[+] Author and Article Information
Reza Abdi Behnagh

Department of Mechanical and
Industrial Engineering,
University of Iowa,
Iowa City, Iowa 52242;
School of Mechanical Engineering,
College of Engineering,
University of Tehran,
Tehran 11155-4563, Iran;
Faculty of Mechanical Engineering,
Urmia University of Technology,
Urmia 57155-3419, Iran

Ninggang Shen

Department of Mechanical and
Industrial Engineering,
University of Iowa,
Iowa City, Iowa 52242

Mohammad Ali Ansari, Morteza Narvan, Mohammad Kazem Besharati Givi

School of Mechanical Engineering,
College of Engineering,
University of Tehran,
Tehran 11155-4563, Iran

Hongtao Ding

Department of Mechanical and
Industrial Engineering,
University of Iowa,
Iowa City, Iowa 52242
e-mail: hongtao-ding@uiowa.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received May 26, 2015; final manuscript received August 6, 2015; published online October 27, 2015. Assoc. Editor: Gracious Ngaile.

J. Manuf. Sci. Eng 138(4), 041008 (Oct 27, 2015) (11 pages) Paper No: MANU-15-1255; doi: 10.1115/1.4031281 History: Received May 26, 2015; Revised August 06, 2015

In this work, the feasibility to recycle pure magnesium machining chips is first investigated experimentally with a solid-state recycling technique of friction stir extrusion (FSE). Heat generated from frictions among the stirring chips, die, and mold facilitates the extrusion process. Mechanical tests, optical microscopy (OM), and scanning electron microscopy (SEM) analysis are conducted to evaluate the mechanical and metallurgical properties of extruded wires. Mechanical tests show that almost all recycled specimens can achieve higher strength and elongation than original material of magnesium at room temperature. Due to a refined grain microstructure, good mechanical properties are obtained for samples produced by the rotational speed of 250 rpm and plunge rate of 14 mm/min. A metallo-thermo-mechanical coupled analysis is further conducted to understand the effects of process parameters. The analysis is carried out with a multistep two-dimensional (2D) coupled Eulerian–Lagrangian finite-element (FE) method using abaqus. The material constitutive model considers both work hardening and strain softening. Material grain size evolution is modeled by dynamic recrystallization (DRX) kinetics laws. The deformation process and its consequential microstructural attributes of grain size and microhardness are simulated. Physics principles of the microstructure evolution are discussed based on both experimental and numerical analyses.

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References

Figures

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Fig. 1

Mg chips and microstructures: (a) Mg machined chips; (b) optical micrograph of the base Mg ingot material; and (c) optical micrograph of the machined chips

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Fig. 2

Experimental setup for the FSE process

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Fig. 3

Wires extruded at different conditions

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Fig. 4

Microstructures at the center of fabricated wires in different conditions: (a) F14-250 rpm; (b) F20-250 rpm; (c) F14-355 rpm; and (d) F20-355 rpm

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Fig. 5

Histograms of grain size distribution in the center of wires from (a) F14-250 rpm and (b) F20-355 rpm

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Fig. 6

Fine-grained microstructure in the boundary layer produced by test F20-355 rpm: (a) micrograph and (b) histogram of grain size distribution

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Fig. 7

Tensile test results

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Fig. 8

SEM images of fracture surfaces from tensile tests: (a) F14-250 rpm; (b) F20-250 rpm; (c) F14-355 rpm; and (d) F20-355 rpm

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Fig. 9

Microhardness profile along the radius of the samples after extrusion

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Fig. 10

The CEL modeling configuration

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Fig. 11

Infrared temperature measurement and model predictions at point A: (a) F14-250 rpm; (b) F20-250 rpm; and (c) F14-355 rpm

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Fig. 12

The computation flowchart of material constitutive model

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Fig. 13

Steady-state simulation for condition F14-250 rpm: (a) temperature, (b) equivalent plastic strain, and (c) strain rate

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Fig. 14

Microstructure simulation for condition F14-250 rpm: (a) simulated volume fraction of DRX; (b) grain size; and (c) microhardness distributions

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Fig. 15

The comparison of the experimentally measured and predicted microhardness profile along the radial direction for F14-250 rpm

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Fig. 16

The comparison of the experimentally measured and simulated: (a) average grain sizes and (b) average microhardness for three conditions

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