Forming limit studies on different thickness aluminium 6xxx series alloys used in automotive applications

During sheet metal forming, one of the major measures of success for the material is to show forming strains below the safe limit of a forming limit curve (FLC) and to show minimum thinning in critical areas in the forming die. To understand this behaviour, tensile tests and 7 point FLC tests were conducted to evaluate the forming limit of the alloy using Instron and Erichsen machines respectively. This paper presents the outcome of investigations into the forming characteristics of different thickness of aluminium 6xxx series alloys with T4 and T6 temper and compares them to results obtained from previously published investigations. Metallographic analyses were also conducted on these alloys in order to correlate the microstructure with the observed forming behaviour. The results presented indicate how both material thickness and tempering treatment affect the forming limit of the material.