Semi-solid formed aluminum

The semi-solid forming process offers the near net shape capabilities and process economics of die casting, but produces components that have mechanical properties well in excess of permanent mold castings and approaching those of forgings. These advantages result from the engineered properties of a semi-solid aluminum alloy, and include: less solidification shrinkage than a fully liquid alloy, since the material has already undergone partial freezing; less total heat content than a fully liquid alloy, since the material contains only a fraction of the heat of fusion and is at a lower temperature; significantly higher viscosity, which permits non-turbulent flow at higher filling rates than possible with a fully liquid alloy. These process benefits produce a unique set of performance payoffs. The precise detail and dimensional repeatability permit near net shape designs and the avoidance or reduction of costly secondary machining operations. The highly viscous filling characteristics of the semi-solid aluminum alloy reduces the potential for air and die-lubricant entrapment, which can compromise component integrity and mechanical performance. The engineered microstructure of discrete, small-diameter alpha particles, and the very high solidification rate resulting from pressurized metal mold cooling, result in very fine microstructural detail.