On the Microstructural Homogeneity and Mechanical Properties of Al 6063 Alloy Processed by the Cyclic Expansion Extrusio
- PDF / 9,181,209 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 16 Downloads / 181 Views
JMEPEG https://doi.org/10.1007/s11665-020-05151-8
On the Microstructural Homogeneity and Mechanical Properties of Al 6063 Alloy Processed by the Cyclic Expansion Extrusion Process V. Babu, Balasivanandha Prabu Shanmugavel, and K.A. Padmanabhan (Submitted September 10, 2019; in revised form August 20, 2020; Accepted: 6 September 2020) 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 s21. The CEE die had an extrusion semi-die angle (a) 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 ultrafinegrained 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 lm. 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. Keywords
Al 6063 alloy, cyclic expansion extrusion, electron backscatter diffraction, severe plastic deformation, ultrafine grain
1. Introduction The development of ultrafine-grained (UFG) metals and alloys with grain sizes in the range of 100 nm–1 lm is commercially very important. The UFG structure has been produced using severe plastic deformation (SPD) techniques in which coarse-grained materials are subjected to severe straining by incremental deformation (Ref 1). Grain refinement improves the strength and toughness simultaneously. Severe straining helps develop high densities of defects in the microstructures, including dislocations and twins and also refines the coarse grains into UFG (or) nano-grains (Ref 2, 3). UFG Al alloys, due to their several advantages, have received significant attention in the aerospace and automotive industries. It was established that CEE is a good grain refinement technique to improve the properties of copper and its alloys (Ref 4), Al (Ref 5) as well as Al-alloys (Ref 6, 7). Al-Mg-Si alloys (AA 6063) are used in aviation, transportation, architecture, decoration and automotive structural applications owing to their reduced weight without compromising on the properties required for the applications. For example, AA 6063 alloy has been used in
V. Babu, Balasivanandha Prabu Shanmugavel,
Data Loading...
