Deformation Behavior of the Percolating Intermetallic Microstructure of High Pressure Die Cast AZ91 Alloy

The intermetallic microstructure in two representative regions of the cross section, the corner and the core, of a cast-to-shape tensile specimen was studied. Available 3D data of the intermetallic, obtained with focused dual ion beam tomography, were incorporated into a finite element code to simulate the deformation behavior. The modeling reveals a high structural compliance at both the corner and the core, akin to the bending-dominated behavior of cellular foams. The high compliance suggests that the percolating microstructure should keep most of its structural integrity, reinforcing the alloy without compromising the ductility, for strains above 1%. Scanning electron microscope observations of the damage by cracking of the intermetallic along the gauge of a tensile specimen deformed to fracture supported this prediction.