The role of intermetallic particles on mode I crack propagation mechanisms in metal plates

In metal plates, the crack propagation mechanism sets the amount of the plastic deformation before failure: a slanted or a cup-cone crack typically yields limited plate thinning within the fracture process zone, while large deformation precedes cup-cup crack propagation. The present work investigates the effect of intermetallic particles on the propagation mechanisms and the associated fracture surface morphologies when tearing Al 1050 plates under far-field mode I loading. Both single edge notched and double edge notched tension specimens, with thicknesses ranging from 0.5 to 5 mm, were tested. The chemical compositions of intermetallic particles were determined by performing energy dispersive X-ray measurements, and their morphological features were characterized by Scanning Electron Microscopy (SEM). Likewise, SEM images were taken to display the fracture surfaces, and the details of the surface morphology were visualized in three dimensions by using X-ray Tomography scanning. The experimental results indicate that an increase in the volume fraction, size, and aspect ratio of the intermetallic particles all promote slanted/cup-cone cracks, while a low amount of small, circular particles leads to cup-cup cracks. Furthermore, two-dimensional finite element simulations for mode I crack propagation support the experimental findings.