Microstructure and brittle fracture resistance of layered steel composites produced by explosion welding and pack rolling followed by heat treatment

In the present paper, the microstructure and fracture resistance characteristics of 7-layered composites based on Fe-2Mn-1Si low carbon low alloyed steel and Fe-11Cr-9Ni-2Mo-1Ti maraging steel obtained by two different methods such as explosion welding and hot pack rolling with subsequent heat treatment were investigated. It was shown that an important microstructural features of Fe- 2Mn-1Si steel layers are associated with the formation of a fragmentation zone similar to 10 mu m wide with a size of structural elements 0.5-1.0 mu m near the interface in the welded composites and the appearance of decarburized ferrite zone similar to 50 mu m wide in the hot-rolled composites. According to local energy dispersive X-ray microanalysis, at the interface of welded and hot-rolled composites, the most active diffusion processes near of Fe-2Mn-1Si and Fe-11Cr-9Ni-2Mo-1Ti steel interlayer borders occur during the composites production by pack rolling. It was established that explosion welding makes it possible to retain the initial microstructure of steel blanks, with the exception of a narrow near-weld zone of grain fragmentation. After the subsequent heat treatment of explosively welded and hot-rolled composites, Fe-2Mn-1Si steel layers are characterized by a viscous ferrite(sorbitol)-pearlite microstructure, and Fe-11Cr-9Ni-2Mo-1Ti steel layers possess a martensitic microstructure with strengthening intermetallic particles. From the results of impact tests at temperatures from +20 degrees C to -60 degrees C, it was found that the impact strength KCV and energy of impact loading A of the hot-rolled composites are 2 and 3.5 - 5.4 times higher than the ones of the welded composites, respectively.