Reverse loading-rate sensitivity of tensile fracture energy of smooth and pre-cracked specimens of carbide-free bainitic steel

In this paper, the tensile fracture energies of smooth and pre-cracked specimens of a carbide-free bainitic steel at various loading rates were investigated. It is demonstrated that the tensile fracture energy of smooth specimen decreases gradually with increasing the loading rate and this is related to the gradually decreased TRIP effect due to less amount of martensitic transformation at higher loading rates. However, the tensile fracture energy of pre-cracked specimen increases with the increase of loading rate and this is associated with more M and M/A islands concentrated at the crack tip at lower loading rates.