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Research Papers: Friction & Wear

An Investigation on Transition Between Mild and Severe Wear in Mg–5Al–0.8Zn Magnesium Alloy Using Recrystallization Kinetics Modeling

[+] Author and Article Information
C. Liang, T. F. Su, Y. B. Wang, X. Han, M. L. Yin

Key Laboratory of Automobile Materials,
Ministry of Education,
Department of Materials Science and Engineering,
Jilin University,
Changchun 130025, China

J. An

Key Laboratory of Automobile Materials,
Ministry of Education,
Department of Materials Science and Engineering,
Jilin University,
Changchun 130025, China
e-mail: anjian@jlu.edu.cn

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received November 13, 2014; final manuscript received February 15, 2015; published online March 31, 2015. Assoc. Editor: Satish V. Kailas.

J. Tribol 137(3), 031602 (Jul 01, 2015) (12 pages) Paper No: TRIB-14-1277; doi: 10.1115/1.4029846 History: Received November 13, 2014; Revised February 15, 2015; Online March 31, 2015

Wear behavior of Mg–5Al–0.8Zn alloy was studied using a pin-on-disk type wear apparatus within a load range of 20–380 N and a sliding speed range of 0.1–4.0 m/s. Analyzes on morphology and chemical composition of worn surfaces were undertaken using scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) for determination type of wear mechanism. Investigations on microstructure, plastic strain, and hardness in subsurfaces were carried out using optical microscope and hardness tester for understanding changes in the microstructure and hardness before and after mild to severe wear transition. The subsurface microstructure beneath the worn surface was subjected to a large plastic strain, and experienced strain hardening, dynamic recrystallization (DRX), and melting successively with increasing load or sliding speed. The transition between mild and severe wear was controlled by microstructure transformation from a strain-hardened into a thermal soften DRX microstructure in subsurface. A contact surface DRX temperature criterion is proposed for prediction of transition between mild and severe wear in Mg–5Al–0.8Zn alloy. The mild to severe wear transition loads were predicted under various sliding speeds using DRX kinetics. The validity of the proposed method for prediction of transition between mild and severe wear is also verified in AZ31 and AZ61 alloys.

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Figures

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Fig. 1

XRD pattern of Mg–5Al–0.8Zn alloy

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Fig. 2

Micrographs of microstructure for Mg–5Al–0.8Zn alloy: (a) showing the grain size of α-Mg solid solution phase and distribution of intermetallic particles and (b) showing the details of the microstructure

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Fig. 3

DTA thermogram of Mg–5Al–0.8Zn alloy

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Fig. 4

COF (a) and wear-rate (b) as a function of applied load for tests conducted at different speeds

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Fig. 5

SEM micrographs of worn surfaces of Mg–5Al–0.8Zn alloy under different sliding conditions: (a) 0.1 m/s and 20 N, (b) 0.785m/s and 20 N, (c) 0.5 m/s and 200 N, (d) center location, 0.785 m/s and 200 N, (e) extruded edge, 0.785 m/s and 200 N, and (f) 1.5 m/s and 180 N

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Fig. 6

EDS spectra of worn surfaces of Mg–5Al–0.8Zn alloy under different sliding conditions: (a) 0.1 m/s and 20 N and (b) 0.785 m/s and 200 N

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Fig. 7

Wear mechanism map for Mg–5Al–0.8Zn alloy

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Fig. 8

Measured and calculated transition loads for Mg–5Al–0.8Zn alloy at different sliding speeds

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Fig. 9

Cross-sectional microstructures of Mg–5Al–0.8Zn alloy after sliding at different loads under sliding speed of 0.785 m/s: (a) 20 N, (b) 80 N, (c) 140 N, (d) 140 N, showing the deformed region, (e) 200 N, (f) 200 N, showing the DRX region, (g) 320 N, and (h) 320 N, showing the solidified region and DRX region

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Fig. 10

Micrographs of microstructures at a depth of about 15 μm in subsurfaces of worn specimens tested at: (a) 80 N, (b) 80 N, showing high density of twins, (c) 120 N, (d) 120 N, showing refined DRX α-Mg grains, (e) 140 N, showing refined DRX α-Mg grains and Mg17Al12 phase particles, (f) 160 N, showing refined DRX α-Mg grains and less Mg17Al12 phase particles, and (g) 180 N, showing solidified microstructure

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Fig. 11

Variations in equivalent plastic strains with depth from surface for Mg–5Al–0.8Zn alloy tested at 20 N, 80 N, and 140 N under 0.785 m/s

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Fig. 12

Variation in hardness with depth from surface at different load ranges: (a) 20–140 N and (b) 140–260 N

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Fig. 13

Hardness of worn surfaces of Mg–5Al–0.8Zn alloy subjected to different loads and sliding speeds

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Fig. 14

Measured and calculated transition loads for as-cast AZ31 and hot deformed AZ61 alloys at different sliding speeds

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