EN-GJMW-400-5 | Annealing B

The photos illustrate a white malleable cast iron after several days of annealing. The malleable carbon has diffused out of the complete cross-section and left cavities.
In the oxidised edge area, Fe-Si oxides have formed at the grain boundaries. The edge structure is purely ferritic, but pearlite is also found in the core.
The SEM images show a force fracture by tensile testing. The residual cavities of the former tempered coal, which are preferentially exposed during fracture, can be seen impressively.
The iron matrix fractures partly ductile, partly brittle by cleavage fracture.