Displacement method

Method to examine the solidification morphology whereas the examination method is based on the principle that residual melt is displaced from hardened crystallite.

The success of this method requires several conditions:

a) The liquid which is used for displacement has to have a low solubility in the melt to be examined.

b) The displacement melt density has to be higher than the examination melt density. Only if this is given, it can be displaced to the top form the the partially hardened zone of the solidification front.

c) The displacement alloys melting temperature has to be lower than the examination melt one, i.e. hardened crystallites may not melt again.

In case od Al or Cu alloys, liquid lead is often used, in case of die cast copper may also be used as displacement melt (according to S. Engler, P. Reisener).