Microstructure and Hemming Properties of AA6016 Aluminum Alloy Sheets

Abstract

The use of Al-Mg-Si-(Cu) heat treatable 6xxx alloys is steadily increasing in the automotive industry. The possibility of weight reduction of the cars in combination with the good formability and high in-service dent resistance of these alloys, make them a favorable material for body panel applications. One of the most common, environment-friendly and easy to perform processes used to join aluminum sheets, is the hemming joining operation. This operation heavily relies on the bendability of the sheets, because they are bent to an angle of 180° over of a radius equal to their thickness. Tearing or cracking of the outer bent surface are often very common. In this study we attempt to understand the relations between the microstructural features of the sheets and their hemming behavior. The hemming experiments are performed in laboratory conditions and the results are discussed together with the data obtained from crystallographic, microstructural and textural investigations. Relations between the hemming appearance, chemical composition, natural aging time and dispersoid’s density are found and discussed.

Microstructure controlled bending response in AA6016 Al alloys

“…This fact gives a clue that the fracture mechanisms involved in this grade during bending does not necessary include formation of voids around constituent particles and their further interaction with the propagating shear bands. The EDX analyses of those particles show higher content of Mn in grade B than in grade A [18] which is in agreement with the chemical composition of these alloys -cf. Table 1.…”

Influence of quench rate and microstructure on bendability of AA6016 aluminum alloys

“…In alloys with excess Si, pure Si particles are known to precipitate [8,11,[32][33][34], and have previously been observed as nanometricsize grain boundary particles [25]. Nanometric-size Mg 2 Si particles are also commonly observed in T4 conditions, both along grain boundaries [25,26] and within grains [35].…”

Recycle-Friendly Aluminum Alloy Sheets for Automotive Applications Based on Hemming

“…The bendability difference of various iron content rass is affected mainly by grain size [13], grain orientation [14,15], micrometer-sized intermetallic particles [8], shear bands [16], grain boundary particle density [17], and precipitationfree zones [18] (short for PFZs) adjacent to the grain boundaries. Quenching and hot-rolling reduction rates affected the hemming ability, as shown in Figs.…”