When bending aluminum alloy, how should the layout be made concerning the material's grain?

In bending aluminum alloy, the orientation of the grain plays a crucial role in the performance and integrity of the bend. When a bend is positioned at 90° to the grain, it maximizes the strength and ductility of the material in the bent area. This is because aluminum alloys have a pronounced grain structure that affects their mechanical properties, particularly their ability to deform without cracking.

By bending at a right angle to the grain, you leverage the material's ductility, allowing it to stretch and compress appropriately during the bending process. This helps avoid issues such as cracking or deformity that can occur if the bend runs parallel to the grain or in alignment with it, which may not provide the necessary flexibility or strength.

Other options either do not capitalize on the material's inherent properties or suggest orientations that might compromise the structural integrity of the bent section. Thus, positioning the bend at 90° to the grain is the optimal approach in sheet metal practices for aluminum alloys.