Stress state effect on dynamic strain aging and surface markings during stretching of AlMg7 alloy sheet

Abstract

Stress state effect on dynamic strain aging (DSA) and the related surface appearance was analyzed in uniaxial and biaxial room temperature stretching of AlMg7 alloy sheet. In uniaxial tension the serrated yielding was found pertinent at the entire strain range for the tested material. Stretcher markings, usually noted as A ("flamboyant") type, formed during yield point elongation, while type B ("parallel bands") appeared at higher strains, due to the Portevin Le Chatelier effect. Stretching the tested sheet material over an hemispherical punch, and simulating a different degree of biaxiality, the dynamic strain aging (DSA) appeared to be suppressed by increasing the biaxiality, and accordingly the surface morphology was also changed in a complex manner