Grain refinement and mechanical properties at elevated temperature of Al-Mg alloy by hard-strain-process

By use of an Equal-Channel-Angular-Extrusion (ECAE) process, the structure of Al-Mg alloy (AA5056) was refined to be less than about 0.3 mu m. The grain refinement was simply caused by an interaction between highly shear strain and thermal recovery during ECAE processing. The deformation behavior of the as-ECAE processed AA5056 alloy with a very refined structure has been investigated by tensile testing at initial strain rates from 10(-5) to 10(-3) s(-1) at temperatures between 473 and 548 K. The total elongation of the ECAE processed alloy was twice as high as that of an unstrained annealed alloy (AA5056-O) with a large grained structure, though flow stresses in both alloys were nearly equal when tested at an initial strain rate of 10(-3) s(-1) at a temperature of 473 K. Also the elongation increases with increasing temperature from 100 to about 200 %. Surface observations reveal that the dominant deformation mechanism of samples tested at higher temperatures is grain boundary sliding.