Effect of electric current pulse on grain growth in superplastic deformation of 2091 Al-Li alloy
(1. School of Materials Science and Engineering,
Central South University, Changsha 410083, China;
2. School of Metallurgy and Materials,
Northeast University, Shenyang 110006, China)
Central South University, Changsha 410083, China;
2. School of Metallurgy and Materials,
Northeast University, Shenyang 110006, China)
Abstract: The effect of electric current pulse on the grain growth in the superplastic deformation of 2091 Al-Li alloy was investigated. Optical metallographic microstructure observation and average linear intercept measuring results show that at same strain， the grain size in the superplastic deformation loaded with electric current pulse is smaller than that unemploying electric current pulse, and so does the grain growth rate. TEM observation shows that the dislocation density at grain boundary in the superplastic deformation applied with electric current pulse is lower than that unemploying electric current pulse.It indicates that electric current pulse increases the rate of dislocation slip and climb in grain boundary, which leads to a decrease of both the density of the dislocation slipping across grain boundary at same strain rate and the driving force for grain growth, therefore the rate of grain growth decreases.The established model for grain growth shows an exponential relation of grain size with strain.
Key words: Al-Li alloy; grain growth; current pulse; superplastic; deformation