EFFECT OF THE BIMODAL STRUCTURE PROCESSED BY ECAP AND SUBSEQUENT ROLLING ON STATIC STRENGTH AND SUPERPLASTICITY OF Al-Mg-Sc-Zr ALLOY

Microstructure and mechanical properties of the 1570C aluminum alloy were studied after equal channel angular pressing (ECAP) to the strain of 3 at 325 degrees C and subsequent warm and cold rolling with near 80% reductions at 325 degrees C and 20 degrees C, respectively. Even containing a partially recrystallized bimodal structure with a volume fraction of ultrafine grains of 0.3 and their size not exceeding 2 mu m, the alloy after ECAP demonstrated an excellent balance of room temperature static strength parameters (yield strength (YS) approximate to 300 MPa, tensile strength (UTS) approximate to 400 MPa and elongation (El) approximate to 26%), and high strain rate superplasticity (with maximum elongation exceeding 2500% at 520 degrees C and a strain rate of 1.4 x 10(-2) s(-1)). Subsequent warm and cold rolling resulted in an increase in YS to 340 and 430 MPa and UTS to 415 and 485 MPa amid El decreased to 24 and 11%, respectively. Despite the difference in the deformation structures formed in both rolling states, similar superplastic behavior was observed with maximum elongations of up to 3000% at temperatures of 500-520 degrees C and strain rates of about 10(-2) s(-1). It was concluded that the initial processing of the alloy to relatively low ECAP strains before warm/cold rolling, leading to bimodal structure with a low fraction of ultrafine grains, is sufficient to ensure a favorable combination of both service and technological properties of the sheets obtained.