Dynamic compressive deformation behaviour of S50C medium carbon steel

Abstract

This paper discusses the effects of strain rate and temperature on the mechanical response and microstructure of annealed plain medium carbon steel S50C subjected to compressive deformation by the split Hopkinson pressure bar. It is found that the flow stress increases with strain rate but decreases with temperature. The material temperature sensitivity parameter increases with increasing strain rate. Both the strain rate sensitivity parameter and the activation volume vary with loading rate and temperature. A constitutive equation based on the Zerilli – Armstrong bcc model describes the high strain rate plastic behaviour of S50C very well. The microstructure is analysed by transmission electron microscopy. The dislocation density and dislocation tangle both increase with strain rate, showing the formation of smaller dislocation cells at higher strain rates. As the temperature is raised, the disappearance of dislocations and the dissolution of cementite occur more easily. These data give much information on the dynamic deformation behaviour of S50C medium carbon steel, with particular applicability for high speed fabrication processes such as rolling and forging.

Keywords:

• MEDIUM CARBON STEEL
• STRAIN RATE
• IMPACT RESPONSE
• DISLOCATIONS
• DYNAMIC RECRYSTALLISATION