Macrosegregation in thin walled castings produced via the direct squeeze casting process

Abstract

Squeeze casting offers significant gains in material properties in relation to other casting techniques. Acceptance of the process suffers from a lack of design criteria and understanding of the process. A common problem of producing castings via this method is segregation in thin walled components. While this phenomenon is apparent in most casting techniques, in squeeze casting the driving force is supplied by the squeezing load not just the force from solidification shrinkage thus it becomes a significant problem. The primary causes of the segregation are surface tension, of the molten alloy, and the design of the component. Using the pressure difference across a curved surface and equating this to the pressure due to depth the minimum web width for no significant segregation can be estimated. This estimation has been verified for LM25. Thus components can be designed with walls of minimum thickness and minimum radius for corners for production using the squeeze casting technique.