Effect of heat treatment process on microstructure and properties of NbVTi alloyed gray iron

Microstructure and mechanical properties of newly developed NbVTi alloyed gray iron after heat treated at different temperatures for different time, were studied by means of scanning electron microscopy (SEM) and mechanical property tests. The results show that with the increase of holding time or temperature, cicular bainite becomes thicker and shorter, meanwhile, graphite gets thicker and longer. The tensile fracture of NbVTi alloyed gray iron is quasi-cleavage fracture. Ductile rupture characteristics appear on the fracture which lead to improvement of the alloy's plasticity and toughness. The tensile strength and Brinell hardness of NbVTi alloyed gray iron decrease with the increase of holding time or temperature.