Why is the sound speed of nodular cast iron lowered after heat treatment?
Sound travels faster in a solid than it does in a liquidOr so, after heating, the intermolecular repulsion decreases, so that the same potential energy conduction requires molecules to move more distances, making the transmission slower
This may be the material microstructure changes after heat treatment, is generally the pearlite content increased, the available change heat treatment and then check the corresponding microstructure and corresponding measuring sound velocity adjustment, such as annealing, normalizing etc..
After the heat treatment, the microstructure of the material changes, the graphite changes, eliminating the internal stress of molecules, thus slowing down the speed.
