Hot deformation behavior and microstructure evolution of carbon nanotube/7055Al composite

In this study, carbon nanotube (CNT) reinforced 7055Al composite was fabricated by high energy ball milling combined with powder metallurgy. The as hot-pressed composite had an inhomogeneous microstructure composed of coarse grains without CNTs and fine grains with uniformly dispersed CNTs. Processi...

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Bibliographic Details
Published in:Journal of alloys and compounds 2021-02, Vol.854, p.157275, Article 157275
Main Authors: Ma, K., Liu, Z.Y., Zhang, X.X., Xiao, B.L., Ma, Z.Y.
Format: Article
Language:English
Subjects:
Abnormal grain growth
Aluminum matrix composite
Ball milling
Boundaries
Carbon nanotube
Carbon nanotubes
Crack propagation
Cracks
Energy dissipation
Evolution
Grain growth
High temperature
Hot deformation
Microcracks
Microstructure
Nucleation
Powder metallurgy
Process mapping
Strain rate
Stress concentration
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Summary:In this study, carbon nanotube (CNT) reinforced 7055Al composite was fabricated by high energy ball milling combined with powder metallurgy. The as hot-pressed composite had an inhomogeneous microstructure composed of coarse grains without CNTs and fine grains with uniformly dispersed CNTs. Processing maps were established and the hot deformation behavior as well as the microstructure evolution during deformation was investigated. It was indicated that the power dissipation efficiency of the composite was relatively lower at higher deformation temperature or lower strain rate. Abnormal grain growth (AGG) and cracking occurred when the composite was deformed at high temperature with low strain rate. A few of CNTs were embedded into coarse grains as AGG occurred, and the micro-cracks formed at the boundaries between the coarse and the fine grained zones. The cracking mechanism was considered as the stress concentration caused by the dragging effect of CNTs, and the reduced critical stress required for pore nucleation due to AGG at the boundaries between the coarse and the fine grained zones. [Display omitted] •Initial CNT/7055Al composite had an inhomogeneous microstructure.•The power dissipation efficiency was low at high temperature and low strain rate.•Abnormal grain growth (AGG) increased stress concentration and led to cracking.•AGG was caused by the migration of coarse - fine grain boundaries.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2020.157275