The Effect of Cerium on Superplasticity of AL-6CU-0.35 MG-0.2ZR Alloy

ABSTRACTThe effect of Cerium addition on the superplasticity of Al-6Cu-0.35Mg-O.2Zr alloy is investigated. The superplastic elongation of the alloy is increased from 450% to 500–700% by the addition of 0.5wt% Cerium, with some decrease in superplastic tensile resistance, when the alloy is deformed at 789K(516°C) with a strain rate of 8.33×10−4S−1. Microstructure observation shows that the addition of Cerium decreases the grain growth rate both in static annealing and during superplastic deformation. This is considered to be the result of the enhanced pinning of fine Zirconium-rich precipitates and the additional pinning of Cerium-rich phase particles. TEM and X-ray diffraction analysis show that Cerium in the alloy forms Cerium-rich phases (AlgCu4Ce and Al4CuCe), and these phase particles join in the pinning of second phase particles on grain boundary, stablizing the microstructure. The addition of Cerium also affects the distribution of Zirconium and Zirconium Aluminide in the alloy.