On the Microstructural Homogeneity and Mechanical Properties of Al 6063 Alloy Processed by the Cyclic Expansion Extrusion Process

Autor: K. A. Padmanabhan, Balasivanandha Prabu Shanmugavel, V. Babu
Rok vydání: 2020
Předmět:
Zdroj: Journal of Materials Engineering and Performance. 29:6870-6880
ISSN: 1544-1024
1059-9495
DOI: 10.1007/s11665-020-05151-8
Popis: This work reports the severe plastic deformation processing of aluminum alloy 6063 (AA 6063) at a temperature of 130 °C (0.2 Tm of AA 6063) up to 6 passes using the cyclic expansion extrusion (CEE) process at a pressing velocity of 0.5 mm s−1. The CEE die had an extrusion semi-die angle (α) of 30°. The effects of plastic deformation on the microstructure and mechanical properties were studied after every two passes by determining the micro-hardness, and tensile properties, and performing an electron backscatter diffraction (EBSD) analysis. The severe strain introduced by plastic deformation gives rise to ultrafine-grained structures with improved strength and hardness properties. The EBSD analysis revealed the refinement of (average) grain size from the starting material grain size of 22 ± 5 to 3 ± 1 µm. The EBSD analysis and transmission electron microscope (TEM) observations confirmed the formation of fine grains with high-angle grain boundaries (HAGBs). Nano-sized grains of d ~ 50 nm and ultrafine grains (up to d ~ 300 nm) could also be seen at the end of 6 passes which, however, occupied only 8% of the total volume. Likewise, the micro-hardness value showed a significant increase through grain refinement. The ultimate tensile strength of AA6063 improved by ~ 87% compared to parent material. In addition, the role of HAGBs and LAGBs in the strengthening mechanisms is discussed.
Databáze: OpenAIRE
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