Low-temperature superplasticity of Al2O3(p)/Ni–Co nanocomposites

Nanocomposites of Al2O3/Ni–Co prepared using Al2O3 of various particle sizes were fabricated by pulse current electrodeposition. Their superplastic tensile deformation was investigated at strain rates of 8.33 × 10−4 s−1 and 1.67 × 10−3 s−1 and temperatures of 723–823 K. The Al2O3 particle sizes and the deformation temperature had significant influence on the elongation of the deposited materials. The optimal superplastic condition and the maximum elongation were determined. A low temperature superplasticity with elongation of 632% was achieved at a strain rate of 1.67 × 10−3 s−1 and 823 K. Scanning electron microscopy and transmission electron microscopy were used to examine the microstructures of the deposited and deformed samples. The grains grew to a micrometer dimensions and were elongated along the tensile direction after superplastic deformation. Superplasticity in electrodeposited nanocomposites is related to the presence of S at grain boundaries and to deformation twinning.

► Al2O3/Ni–Co nanocomposites were fabricated and their superplastic tensile deformation behaviors were investigated. ► Optimal superplastic condition and the maximum elongation were determined. ► The microstructures were observed to analyze the influence of Al2O3 particles size on the superplasticity. ► The superplasticity in electrodeposited nanocomposites is related to the presence of S and deformation twinning.