Low-temperature superplasticity of Al 2O 3(p)/Ni–Co nanocomposites

Abstract

Nanocomposites of Al 2O 3/Ni–Co prepared using Al 2O 3 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 Al 2O 3 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.