Property Criteria for Automotive Al-Mg-Si Sheet Alloys

Abstract

In this study, property criteria for automotive Al-Mg-Si sheet alloys are outlined and investigated in the context of commercial alloys AA6016, AA6005A, AA6063 and AA6013. The parameters crucial to predicting forming behavior were determined by tensile tests, bending tests, cross-die tests, hole-expansion tests and forming limit curve analysis in the pre-aged temper after various storage periods following sheet production. Roping tests were performed to evaluate surface quality, for the deployment of these alloys as an outer panel material. Strength in service was also tested after a simulated paint bake cycle of 20 min at 185 °C, and the corrosion behavior was analyzed. The study showed that forming behavior is strongly dependent on the type of alloy and that it is influenced by the storage period after sheet production. Alloy AA6016 achieves the highest surface quality, and pre-ageing of alloy AA6013 facilitates superior strength in service. Corrosion behavior is good in AA6005A, AA6063 and AA6016, and only AA6013 shows a strong susceptibility to intergranular corrosion. The results are discussed below with respect to the chemical composition, microstructure and texture of the Al-Mg-Si alloys studied, and decision-making criteria for appropriate automotive sheet alloys for specific applications are presented.

Design strategy for controlled natural aging in Al–Mg–Si alloys

“…This generates two problems for the transportation industry: first, dynamic hardening during n.a. reduces formability [4]; second, clustering results in a negative effect of n.a. on subsequent artificial aging (a.a.) [12,13,[16][17][18].…”

“…on subsequent artificial aging (a.a.) [12,13,[16][17][18]. The transportation industry, however, requires several months of stable formability combined with good a.a. performance so as to obtain reproducibility of designs that have increasing complexity [4,10]. Hence, pre-aging treatments have been developed to improve a.a. and to achieve a relatively "stable" material state [8,10,[19][20][21][22].…”

“…The delivery of semi-finished products mostly occurs after quenching to enable forming operations at low strength prior to the final heat treatment to gain high strength [4,[8][9][10].…”

“…6xxx-series alloys are especially attractive as they combine good formability with medium to high strength after age hardening, good corrosion resistance, and weldability. In the automotive industry, for example, they are used as outer skin alloys, for non-decorative inner parts, and structural or crash components with individual property criteria [1][2][3][4][5]. Yet, the ever-growing demand to increase formability and strength for more complex parts of lower weight drives the alloy development considerably [4][5][6][7].…”

Voids and Microstructure Evolution in Aluminium Sheets during High Deformation

“…The bending performances can be affected negatively by intermetallic particles naturally presented in such alloys. In addition this alloy present moderate strength, good corrosion resistance and surface quality regarding roping [3]. Other factor is the influence of the microstructure on the mechanical properties of this alloy and on his resistance during service as the final auto part.…”