High strain-rate superplasticity of ultrafine-grained Al-Mg-Mn-Zn-Zr alloy

The microstructure evolution in 1565ch alloy of the Al-Mg-Mn-Zn-Zr system during thermomechanical treatment including severe plastic deformation and subsequent isothermal rolling at a temperature of 200 degrees C is studied. The treatment resulted in the formation of an ultrafine-grained (UFG) structure with regulated distribution of Al6Mn, Al3Zr and Al3Mg2 phases both in the body and along the grain boundaries in 1565ch alloy which made it possible to implement the effect of superplasticity (SP) at 300 degrees C and high strain rates of 5 x10(-2), 10(-2) and 5 x10(-3) s(-1). The deformation relief formed on the gauge part of UFG 1565ch samples at the stage of a steady-state SP flow is analyzed. It has been established that high-rate SP at a temperature of 300 degrees C occurs by a combination of cooperative grain-boundary sliding and intragranular dislocation slip.