Exploring Design and Manufacturing Causes for Failure of Zambian Cast Aluminum Pots

Recycled cast aluminum elevated pots, made in rural Zambia by independent craftspeople, have been reported to fail due to brittle fracture of their legs with the application of minimal force.  Optical emission spectroscopy shows that these fractures are likely due to the inclusion of iron-based intermetallic compounds increasing the likelihood of fracture in the cast alloy.  A controlled simulation of the casting process determined that the use of a reclaimed iron crucible is a notable cause of iron inclusion in the resulting aluminum alloy. Samples were taken from a graphite crucible of molten aluminum in which an iron rod was submerged for a period of 25 minutes. Six total samples were collected at five minute intervals over the course of the experiment. An X-Ray Fluorescence (XRF) machine was used to determine the percentage by weight of iron in each sample and demonstrated that the 25 minutes of exposure to the iron rod increased the percentage of iron to 5.97% of the material composition. As the removal of the iron inclusions from the cast alloy may not be feasible for pot makers, this paper also proposes alternative designs for the legs of the elevated pot, and analyzes their success in reducing the maximum von Mises stress experienced within the leg of the pot through Finite Element Analysis (FEA).