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Materials 2014, 7(3), 1573-1589; doi:10.3390/ma7031573
Article

Effect of Thermal History on Microstructures and Mechanical Properties of AZ31 Magnesium Alloy Prepared by Friction Stir Processing

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Received: 13 January 2014; in revised form: 6 February 2014 / Accepted: 19 February 2014 / Published: 28 February 2014
(This article belongs to the Special Issue Light Alloys and Their Applications)
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Abstract: Hot-rolled AZ31 (Mg-2.57Al-0.84Zn-0.32Mn, in mass percentage) magnesium alloy is subjected to friction stir processing in air (normal friction stir processing, NFSP) and under water (submerged friction stir processing, SFSP). Thermal history of the two FSP procedures is measured, and its effect on microstructures and mechanical properties of the experimental materials is investigated. Compared with NFSP, the peak temperature during SFSP is lower and the duration time at a high temperature is shorter due to the enhanced cooling effect of water. Consequently, SFSP results in further grain refinement, and the average grain size of the NFSP and SFSP specimens in the stir zone (SZ) are 2.9 μm and 1.3 μm, respectively. Transmission electron microscopy (TEM) examinations confirm that grain refinement is attributed to continuous dynamic recrystallization both for NFSP and SFSP. The average Vickers hardness in the SZ of the NFSP and SFSP AZ31 magnesium alloy are 76 HV and 87 HV. Furthermore, the ultimate tensile strength and the elongation of the SFSP specimen increase from 191 MPa and 31.3% in the NFSP specimen to 210 MPa and 50.5%, respectively. Both the NFSP and SFSP alloys fail through ductile fracture, but the dimples are much more obvious in the SFSP alloy.
Keywords: AZ31 magnesium alloy; friction stir processing; thermal history; microstructure; mechanical properties AZ31 magnesium alloy; friction stir processing; thermal history; microstructure; mechanical properties
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Chai, F.; Zhang, D.; Li, Y. Effect of Thermal History on Microstructures and Mechanical Properties of AZ31 Magnesium Alloy Prepared by Friction Stir Processing. Materials 2014, 7, 1573-1589.

AMA Style

Chai F, Zhang D, Li Y. Effect of Thermal History on Microstructures and Mechanical Properties of AZ31 Magnesium Alloy Prepared by Friction Stir Processing. Materials. 2014; 7(3):1573-1589.

Chicago/Turabian Style

Chai, Fang; Zhang, Datong; Li, Yuanyuan. 2014. "Effect of Thermal History on Microstructures and Mechanical Properties of AZ31 Magnesium Alloy Prepared by Friction Stir Processing." Materials 7, no. 3: 1573-1589.


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