Low-temperature superplasticity of Al_2O_3(P)/Ni-Co nanocomposites

摘要

Nanocomposites of Al_2O_3/Ni-Co prepared using A1_2O_3 of various particle sizes were fabricated by pulse current electrodeposition. Their superplastic tensile deformation was investigated at strain rates ol 8.33 x 1CT4 s"1 and 1.67 x 10~3 s"1 and temperatures of 723-823 K. The A1_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 super plasticity with elongation of 632% was achieved at a strain rate of 1.67 x 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 nanocom posites is related to the presence of S at grain boundaries and to deformation twinning.