High temperature tensile behavior of ultra-fine grained Al-3.3Mg-0.2Sc-0.2Zr alloy by equal channel angular pressing

High temperature tensile tests at temperatures of 293-773 K and initial strain rates of 5×10^-4 to 1×10^-1s^-1 were carried out on Al-3.3Mg-0.2Sc-0.2Zr alloy prepared by equal channel angular pressing (ECAP) at 473 K. The microstructure of the alloy before and after ECAP was investigated by TEM and XRD. The results showed that the intensities of (1 1 1)/(2 2 2) and (2 0 0)/(4 0 0) peaks for the ECAPed alloy decrease significantly and the peak widths at half height become broadening in comparison to the corresponding values for the alloy before ECAP. The equiaxed ultra- fine grains of ∼0.2 μm were obtained in the alloy after eight pass ECAP. The distribution of Sc and Zr elements and the second phase particles was homogeneous in the specimen after ECAP. The ultra-fine grained microstructure was stable below 773 K because the alloy retained extremely fine grain size of ∼1 μm after static annealing at 773 K for 1 h. When tested at 293 K and strain rates varying from 5×10^-4 to 1×10^-1s^-1, the alloy showed strain rate insensitive plasticity. When tested at 523, 623 or 773 K, there were monotonous increases in maximum flow stress and decreases in ductility with the increasing of strain rates. The maximum elongation to failure of 365% was obtained at 773 K and 5×10^-4s^-1.