Investigations on the hot workability characteristics and deformation mechanisms of aluminium alloy-Al2O3 nanocomposite

• Al7075–Al2O3 nanocomposite is successfully fabricated using stir-casting process.
• Flow analysis indicated occurrence of dynamic recovery and recrystallization.
• Constitutive equation is developed to estimate the load and power requirements.
• Processing map is generated – the safe zone obtained is larger than matrix alloy.
• The deformation mechanisms were confirmed using microstructure analysis.

Hot deformation behaviour analysis of an extruded aluminium alloy-Al2O3 nanocomposite is presented in this paper. The cast-extruded nanocomposite specimens were subjected to hot compression test in the temperature range of 573–773 K and in the strain rate range of 0.001–0.1 s−1 up to a strain of 0.5. The constitutive equations relating the strain rate and flow stress were developed for the fabricated nanocomposite. The average activation energy for the aluminium nanocomposite is found to be 307.23 kJ/mol, which is significantly larger than the 196 kJ/mol value of the corresponding matrix alloy. The processing map was developed and the kinetic analysis was carried out to arrive at the optimum operating conditions. The optimum hot working zone is found to be the temperature region of 620–740 K with strain rate of 0.01–0.1 s−1. In the case of Al–Al2O3 nanocomposite, the safe region obtained is significantly larger in size compared to that of matrix alloy. When the strain was increased up to 0.7 in the instability zone, surface cracking was observed. Microstructure analysis had also been done to verify and validate the deformation mechanisms.

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