The effects of combined cyclic close die forging and aging process on microstructure and mechanical properties of AA7075

It is well known that applying severe plastic deformation methods on the precipitation hardenable aluminum alloys at room temperature is very difficult because of crack formation and segmentation of the specimen during the processes. In this study, several procedures were experimentally examined for...

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Bibliographic Details
Published in:Proceedings of the Institution of Mechanical Engineers. Part L, Journal of materials, design and applications Journal of materials, design and applications, 2020-09, Vol.234 (9), p.1242-1251
Main Authors: Moazam, MA, Honarpisheh, M
Format: Article
Language:English
Subjects:
Aluminum base alloys
Die forging
Electron microscopy
Grain size
Guinier Preston zone
Mechanical properties
Microhardness
Microscopy
Microstructure
Plastic deformation
Quench hardenability
Room temperature
Segmentation
Solid solutions
Tensile stress
Water quenching
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Summary:It is well known that applying severe plastic deformation methods on the precipitation hardenable aluminum alloys at room temperature is very difficult because of crack formation and segmentation of the specimen during the processes. In this study, several procedures were experimentally examined for performing the cyclic close die forging (CCDF) and improving the mechanical properties of AA7075. The experimental tests revealed that supersaturated solid solution of AA7075 after water quenching is formable for only about 5 min and performing the CCDF process in this limited time is possible. Optical and scanning electron microscopy and transmission electron microscopy were used to study the microstructure of the processed samples. It was observed that by applying two passes of CCDF, the grain size of the material reduced from 30 µm to about 200–300 nm. In addition, the X-ray diffractometer results demonstrated that Guinier–Preston zone picks of the processed samples are very weak and the equilibrium η-phase does not exist in none of the suggested procedures. Furthermore, it was found that by combining CCDF and aging processes according to the proposed procedures, the mechanical properties of the processed AA7075 were improved when compared with the AA7075-T6. To put it more clearly, micro-hardness, yield strength and ultimate tensile stress of the processed sample were improved as much as 38.6%, 25% and 23%, respectively.
ISSN:1464-4207
2041-3076
DOI:10.1177/1464420720931528