The deformation behaviour and dislocation sub-structure of AISI 4340 alloy steel under high-rate loading conditions are studied. The mechanical characterization of the specimens is performed over a wide range of strain-rate (10-3-5 x 103 s-1) at different strain levels by means of the compression split-Hopkinson bar technique. The dynamic stress-strain response, strain-rate sensitivities, activation volume and deformation mechanisms are determined. The results of these experiments and how they correlate with the effects of strain rate on mechanical behaviour are discussed also. Based on the stress-strain results, a constitutive equation which accounts for the effect of work hardening and strain-rate sensitivity on the stress is suggested. The variations of the dislocation configurations produced by deformation for each test condition are investigated using the transmission electron microscopy technique (TEM). Experimental observations reveal structural differences between specimens deformed at very high strain-rate, the dislocation density, cell structure and cell size being found to be related to the strain, strain-rate and flow-stress levels.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Computer Science Applications
- Metals and Alloys
- Industrial and Manufacturing Engineering