MICROSTRUCTURE AND PROPERTIES EVALUATION OF DUCTILE CAST IRON SUBJECTED TO HOT PLASTIC DEFORMATION AND AMBIENT TEMPERATURE COMPRESSION

The as-cast microstructure of ductile cast iron (DI) was investigated using light microscopy (LM) and SEM techniques. Further the influence of hot plastic extrusion at 1000(degrees)C with plastic strain in the range of 20-60-80% on the transformation of the as-cast microstructure and on the mechanical properties was studied. Besides this, the microstructure of DI subjected to hot extrusion after the fracture of the corresponding samples induced by compression tests was thoroughly investigated. It was found that compression had a dramatic influence on a shear deformation and hence shear fracture of the compressed samples. It was shown that the shear fracture of the hot deformed ductile iron is accompanied by the occurrence of a narrow zone of severe plastic deformation. The fracture surfaces of the extruded samples subjected to the tensile tests and the compression tests were examined.