Grain boundary and grain interior strengthening in nano-micron grain sized Cu-1wt.%Al₂O₃ composite

ABSTRACT

A bulk Cu-1 wt%Al₂O₃ composite was synthesised to 97–99% theoretical density by mechanical alloying and spark plasma sintering to get varying grain sizes in the range 70 nm–2 µm. Tensile tests were done at room temperature, and the substructure evolution was examined as a function of the grain size and strain. The flow property revealed bilinear Hall–Petch relationship with a transition at 0.55 µm grain size. The stress–strain curves were found to follow the Hollomon-type relationship exhibiting an increase in strength coefficient and a decrease in strain hardening exponent with decreasing grain size. The variations in flow stress with grain size and strain delineate equivalent effects. The inter-dependence between the grain size and strain is explained by the substructure evolution and its contribution to the partitioning of work hardening between the grain interior and grain boundaries.

KEYWORDS:

• Stress–strain behaviour
• Composites
• Powder methods
• Electron microscopy
• Grains and interfaces
• Nanocrystalline materials

Acknowledgements

The authors are grateful to the Director, ARCI, for his support and facilities provided. Acknowledgments are also due to Mr P.V.V. Srinivas for his help in spark plasma sintering.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used are from the Ph.D. work of the first author and the same is under consideration for further extension of the work. In view of this, the authors will not be able to submit the data at this stage.