Testing of liquid and solidification contraction of aluminium alloys

THE shrinkage of metals in the mold can be divided into three distinctly different steps : (a) liquid contraction during cooling of the metal from the pouring temperature to the solidification temperature, (b)solidification contraction as it passes from the liquid to the solid state, between the liquidus and solidus temperatures, and (c) solid contraction as the solid casting cools to room temperature. The first two forms of contraction are mainly responsible for the formation of shrinkage cavities in
casting and the solidification contraction is by far the
most important in this respect. The solid contraction
appears as the reduction of linear dimensions of the
solidified casting as compared with the mold cavity and
is responsible for warping, hot tearing of castings etc.
While there are sufficient data available in the litera-ture regarding solid contraction and total contraction
of metals, there are relatively few data available for
liquid and solidification contraction of different alloys
due to experimental difficulties involved in their deter-mination