Friction & Wear

In Situ Strengthening of the Aluminum-based Gadolinium Alloy Composite for Tribological Applications

[+] Author and Article Information
Brady Barkley, Carlos Sanchez

 Mechanical Engineering, Texas A&M University, College Station, TX 77843

Hong Liang1

 Mechanical Engineering, Texas A&M University, College Station, TX 77843hliang@tamu.edu


Corresponding author.

J. Tribol 134(1), 011603 (Feb 24, 2012) (9 pages) doi:10.1115/1.4005648 History: Received December 07, 2010; Revised October 30, 2011; Published February 21, 2012; Online February 24, 2012

In the present research, a new composite material was developed for increased strength and tribological performance. The gadolinium silicon-germanium compound, GSG, was synthesized into an aluminum substrate to form a composite (GSG-Al). Experimental investigation indicated that the phase transformation of the GSG at its Curie temperature induced significant changes in crystal structures resulting in a giant strain effect. Such an effect increased the wear resistance at a temperature range from −25 °C to 150 °C. The built-in and “self-strengthening” property of such a material is highly desirable for tribological applications. In this manuscript, details of material synthesis, characterization, mechanical, and tribological behavior will be discussed.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

The experimental setup for the two tribometer tests. They contain a tribometer (left), linearly oscillating platform (center), thermocouple and reader (bottom right). Dry ice is placed near the sample for the low temperature tests, while a Mica heater is employed during the high temperature tests.

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Figure 2

XRD phase profiles of GSG-Al (black-labeled) compared with the phase profile of different compounds: (a) GSG (red-unlabeled), (b) Pure aluminum (blue-unlabeled), and (c) aluminum gadolinium germanium (blue-unlabeled)

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Figure 3

GSG-Al sample magnified 100 × with the GSG phase showing sharp and darker phases and the aluminum rich phase being represented by the rest of the portion

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Figure 4

Hardness of sample materials: (a) Rockwell, and (b) Vickers hardness of GSG-Al in regions of mostly aluminum, mostly GSG, mixed regions of GSG, and aluminum phases

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Figure 5

Thermal measurement analysis: (a) linear thermal expansion of GSG-Al, and (b) thickness expansion of GSG-Al with increasing temperature from −18 °C to 8 °C

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Figure 6

Comparison of the coefficients of friction for both GSG-Al and Al 6061-T651at temperatures of −25 °C, 25 °C, 50 °C, and 150 °C

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Figure 7

Coefficient of friction plots for (a) GSG-Al, and (b) Al 6061-T651 conducted at −25 °C for 30 min. Plots for (c) GSG-Al and Al 6061-T651 at 25 °C, and (d) GSG-Al at 25 °C, 50 °C, and 150 °C

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Figure 8

Comparison of the wear rates for GSG-Al and Al 6061-T651 at temperatures of 25 °C, 50 °C, and 150 °C

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Figure 9

Wear debris analysis under TEM from wear tests of: GSG-AL at (a) room temperature, (b) 50 °C, and (c) 150 °C, and Al 6061-T651 at (d) room temperature for comparison. (e) Weight percentage of the different elements contained within the GSG-Al wear test debris at different test temperatures.

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Figure 10

SEM analysis of the wear mechanism. Crack propagation in (a) the GSG-Al sample, and (b) in a sample of Al 6061-T651 at the wear surface. Fractography of (c) GSG-Al, and (d) Al6061-T651, which failed due to tensile stresses.



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