Three-Point Bending of Heat-Treatable Aluminum Alloys: Influence of Microstructure and Texture on Bendability and Fracture Behavior

摘要

Three-point bending tests of extruded aluminum alloys showed lower bendability when the bending axis is aligned with the extrusion direction compared to the transverse direction. In the present work, three different microstructures of a commercial AA7108 aluminum alloy were studied with respect to mechanical properties, texture, constituent particles, and crack propagation. The three different microstructures were an as-cast and homogenized material, a fibrous extruded material, and a cold rolled and recrystallized material. While the mechanical properties in tension are more or less the same for the three materials, the bendability is strongly dependent on the microstructure and the global alignment of constituent particles. The as-cast and homogenized material shows poor bendability due to large grains and constituent particles on the grain boundaries, which leads to decohesion and premature failure. The response of both the fibrous and the recrystallized materials depends on the direction of the bending axis. A strong fiber texture is found to influence the bendability by initiation of shear bands. The crucial fracture mechanism, however, seems to be the global alignment of constituent particles, which is inherited from the deformation process.