Simultaneously improving the strength and ductility of an Al-5.5Mg-1.6Li-0.1Zr alloy via warm multi-pass ECAP

Overcoming the ductility inadequacy while maintaining relatively high strength of Al-Li alloys is in urgent need for developing new low-density and high-performance aerospace aluminum alloys. In this research, a warm multi-pass equal-channel angular pressing (ECAP) process was developed to simultaneously improve the strength and ductility of an Al-5.5Mg-1.6Li-0.1Zr alloy. The effects of the process on the microstructure evolution, plastic deformation and strengthening mechanism were also investigated. Results show that the ultimate strength (UTS) and elongation to failure (EL) of ultrafine-grained (UFG) alloy after 16 ECAP passes at 300 degrees C reach up to 476 MPa and 21.6% respectively, about 74% and 108% higher than those of the as-cast sample with coarse grains. The great improvement can be attributed to the coupling effect of the UFG microstructure and uniform distribution of large number of precipitates.