Relationship between microstructural extremum and fracture path in a cast Al-Si-Mg alloy

Finite element analysis of the stress distributions near damaged Si particle clusters in cast Al–Si alloys

“…However, particles with high aspect ratios consistently show an increased propensity for fracture (Gurland and Plateau, 1963;Yeh and Liu, 1996;Dighe and Gokhale, 1997). In addition, the fracture plane in the silicon is usually perpendicular to the applied loading axis (Gurland and Plateau, 1963;Yeh and Liu, 1996;Dighe and Gokhale, 1997). These two e ects are arguably the most dominant ones observed in micrographs, and they are both predicted by continuum analysis of the particles (Gurland and Plateau, 1963).…”

“…However, despite the fact that particle shape has a strong impact on the fractured silicon particle distribution under monotonic (Gurland and Plateau, 1963;Yeh and Liu, 1996;Dighe and Gokhale, 1997) and cyclic (Gall et al, 1999b) loading conditions, the model did not capture the geometrical aspects of particle fracture. Localized plastic¯ow near the particles will lead to dislocation pileups and hardening at the microscale.…”

“…Particles contained within aluminum alloys are generally classi®ed according to their size (Davidson and Lankford, 1985): precipitates (d`0X02 lm), dispersoids (0X02`d`0X5 lm), and inclusions (d b 1 lm). The silicon particles Mechanics of Materials 32 (2000) 277±301 www.elsevier.com/locate/mechmat in cast Al±Si alloys are considered inclusions since their average size is around 5 lm (Dighe and Gokhale, 1997). It is well established that hard second phase particles dispersed throughout a ductile matrix have a strong in¯uence on the overall ductility (Broek, 1973), fracture toughness (Hahn and Rosen®eld, 1975), and fatigue resistance (Broek, 1969) of aluminum alloys.…”

“…Consequently, the failure of cast aluminum alloys under monotonic loading is very sensitive to the silicon particle morphology. In general, coarse irregular shaped silicon particles promote rapid damage evolution and result in a cast aluminum alloy with low ductility and ultimate tensile strength (Closset and Gruzleski, 1982;Pan et al, 1991;Voigt and Bye, 1991;Samuel and Samuel, 1995;Caceres et al, 1995;Dighe and Gokhale, 1997). Other factors such as high porosity (Samuel and Samuel, 1995) and brittle intermetallics (Murali et al, 1996;Tan et al, 1995, Gall et al, 1999a can also degrade the monotonic properties of Al±Si castings by further facilitating the localization of damage.…”

“…If the mismatch stresses did not in¯uence particle fracture, particles would be expected to fracture in a random distribution, irrespective of the particle geometry. However, particles with high aspect ratios consistently show an increased propensity for fracture (Gurland and Plateau, 1963;Yeh and Liu, 1996;Dighe and Gokhale, 1997). In addition, the fracture plane in the silicon is usually perpendicular to the applied loading axis (Gurland and Plateau, 1963;Yeh and Liu, 1996;Dighe and Gokhale, 1997).…”