Comparsion of forming and fracture limits of an aluminum alloy and austenitic stainless steel

Forming and fracture limits of AA 3104 aluminum alloy and AISI 304 type stainless steel were studied. Hydraulic bulge testing was employed in the stretch forming experiments. Marciniak-type in-plane tests and tensile testing were carried out to study the limit strains in the deep drawing region. Both screen-printed and laser-marked grids were used to measure the surface strains. Although the forming limits of the AA 3104 were generally much lower than the AISI 304 stainless steel, they both failed in stretch forming by ductile shearing in the through thickness direction without any visible local necking. The preferred failure direction for AA 3104 alloy was transverse to the rolling direction, as could be observed in the bulge tests with a circular die. In the Marciniak-type in-plane tests the AA 3104 alloy showed multiple necking similar to what has previously been reported for low-carbon steel. In the tensile testing, central cracking and subsequent local necking as well as local necking without previous central crack formation were observed both for the AA 3104 aluminum alloy and the AISI 304 stainless steel.