Mechanical and anisotropic behaviors of Mg-Li-Zn alloy thin sheets

The suitability of two recently developed aluminium alloys (an Al–Mg–Mn alloy and an Al–Li–Cu alloy) for press forming applications has been examined. The characterisation involved the experimental determination of microstructural aspects, tensile properties, and formability parameters such as average plastic strain ratio and planar anisotropy. The forming limit diagram has been experimentally evaluated. A detailed analysis of the strain distribution profiles obtained from punch stretching experiments has been attempted. An attempt has been made to correlate the crystallographic texture with the formability parameters. The fracture surfaces of the punch stretched samples were observed using scanning electron microscopy with a view to obtaining a correlation between fracture behaviour and formability. The alloys, in particular the Al–Mg–Mn alloy, have been found to possess good stretchability but both show very limited drawability. Texture analysis indicated negligible earing during deep drawing. T...

Formability of two aluminium alloys

Mechanical properties and formability of an Mg–6%Li–1%Zn alloy thin sheet at elevated temperatures

Room temperature formability testing was performed on an AlMg6.8 type alloy sheet with a fully recrystallized structure (average grain diameter ∼18 μm) and after partial annealing with a retained deformed structure. The yield strengths attained after full recrystallization and after partial annealing, were 175 and 283 MPa respectively. Such an increase in strength is followed by formability degradation, maximized around the plain strain state to either 42%, as obtained using the limiting dome height test (LDH), or 35% after using forming limit curves (FLC). A comparison with known high-strength formable alloys has shown that the tested alloy in the recrystallized condition has a better stretch formability (at the same or even higher yield stress level), while in the unrecrystallized-partially annealed condition it has a lower formability, limiting its application to moderate forming requirements for very high-strength parts. © 1998 Chapman & Hall

Formability of a high-strength Al-Mg6.8 type alloy sheet

Uniaxial tension and press forming tests were carried out at two different strain rates and temperatures to investigate the formability of fine-grained AZ31B-O Mg alloy thin sheet. Formability parameters were determined by tensile test results. The tensile properties and formability parameters were correlated with the forming limit diagrams. The present work focused on the effects of loading orientation and deformation rate on formability. Anisotropic behaviors were observed in the mechanical properties. Maximum strengths were obtained in the direction perpendicular to the rolling direction (RD). It can be concluded that the formability of the rolled fine-grained AZ31B-O Mg alloy sheet can be influenced by loading orientation and deformation rate. Stretch formability can be enhanced at a higher deformation rate, resulting from a lower anisotropy and a higher work hardening effect. In contrast, the drawing processes can be performed at a lower deformation rate to take advantage of a higher anisotropic behavior. Specimens with the RD parallel to the major strain in the press forming tests can enhance stretch formability, whereas specimens with the RD perpendicular to the major strain can improve deep-drawability.

D. Ravikumar

Papers

The formability and texture level of a recent automotive stamping grade AI-Mg-Mn alloy