Casting

research contact: Srinath Viswanathan

Numerical simulations of casting processes are used to predict microporosity and other materials defects. Through synergies between ORNL's experimental and simulation programs in casting and solidification, goals of national importance are being achieved in the areas of lightweight materials, enhanced component life, and increased fuel efficiency.

Avoiding surface defects in aluminum 356 alloy motor mount

severe surface defects

Casting quality can be significantly affected by the flow behavior of molten aluminum alloy into the die cavity. The first figure shows an aluminum 356 alloy motor mount which exhibits severe surface defects. The sequence of simulation images illustrates backfill and recirculation in the flow. This is responsible for entrapment of air which forms oxide in reaction with molten aluminum, causing surface defects. Using these simulation results, a modified gating system was developed that eliminates air entrapment, resulting in the shown defect-free motor mount.

defect-free

Three images of simulated oxide-producing backfill and recirculation in the flow

Al-Cu alloy casting simulation

Microporosity defects

Premature failure in cast parts result from microporosity and other shrinkage defects that form during solidification. Such microporosity defects are seen as dark regions in the first image. The simulation images show, respectively, the liquid fraction dirstribution, pressure drop due to solidification shrinkage, corresponding interdendritic fluid velocity, and resulting microporosity distribution in a bar-shaped casting of aluminum-copper alloy.

liquid fraction distribution

pressure drop

interdendritic fluid velocity

microporosity distribution