Journal of Ultrafine Grained and Nanostructured Materials

Journal of Ultrafine Grained and Nanostructured Materials

Analysis of Strengthening Mechanisms in an Artificially Aged Ultrafine Grain 6061 Aluminum Alloy

Document Type : Research Paper

Authors
Mohammad Reza Rezaei 1
Mohammadreza Toroghinezhad 2
Fakhreddin Ashrafizadeh 2
1 School of Engineering, Damghan University, Damghan, Iran.
2 Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
10.22059/JUFGNSM.2017.02.10
Abstract
The current study adopted a quantitative approach to investigating the mechanical properties, and their relationship to the microstructural features, of precipitation-strengthened 6061 aluminum alloy processed through accumulative roll bonding (ARB) and aging heat treatment.  To serve this purpose, the contributions of different strengthening mechanisms including grain refinement, precipitation, dislocation and solid-solution strengthening to the yield strength of five-cycle ARB samples processed under pre-aged (ARBed) and aged (ARBed+Aged) conditions were examined and compared. Microstructural characterizations were performed on the samples through the transmission electron microscope (TEM) and X-ray diffraction (XRD). Also, the mechanical properties of the samples were investigated through the tensile test. The obtained results showed that an equiaxed ultrafine grain structure with nano-sized precipitates was created in the both ARBed and ARBed+Aged samples. The grain refinement was the predominant strengthening mechanism which was estimated to contribute 151 and 226 MPa to the ARBed and ARBed+Aged samples, respectively, while the dislocation and Orowan strengthening mechanisms were ranked second with regard to their contributions to the ARBed and ARBed+Aged samples, respectively. The overall yield strength, calculated through the root mean square summation method, was found to be in good agreement with the experimentally determined yield strength. It was also found that the presence of non-shearable precipitates, which interfered with the movement of the dislocations, would be effective for the simultaneous improvement of the strength and ductility of the ARBed+Agedsample .
Keywords
Accumulative roll bonding (ARB)
Aging
Strengthening mechanisms
Microstructure
Mechanical properties
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Journal of Ultrafine Grained and Nanostructured Materials
Volume 50, Issue 2
December 2017
Pages 152-160

  • Receive Date 17 September 2017
  • Revise Date 04 December 2017
  • Accept Date 04 December 2017