Microstructure and hemming properties of AA6016 aluminum alloy sheets

摘要

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.