Low-cycle fatigue behaviour and fracture feature of stainless-clad bimetallic steel

The stainless-clad (SC) bimetallic steel that is manufactured by metallurgically bonding stainless steels as cladding metal and conventional mild (CM) steel as substrate metal, is a kind of advanced steel with low cost, high strength and outstanding corrosion-resistant performance. Such advanced steels are especially competitive in the application of engineering structures with demands of high corrosion resistance. Unfortunately, the cyclic behaviour of the SC bimetallic steel is different from that of CM steel or stainless steel, and the research work on the SC bimetallic steels from material level to structural design level for the applications in structural engineering field is very limited. Therefore, this paper aims to investigate the low-cycle fatigue behaviour of the SC bimetallic steel made by hot roll bonding of austenitic stainless steel (S31603) and CM steel (Q355B). The test adopted a constant strain amplitude cyclic loading system with strain ratios of -1 and 0, a strain rate of 0.5%.s(-1) and strain amplitudes varying from 1.00% to 2.50%. The fracture feature, cyclic characteristic, stress-strain response and the influence of surface defect and strain rate are analysed herein, and the strain-fatigue life curves are fitted and predicted by adapting the Basquin-Coffin-Manson model and Kuroda model. Research outcomes show that the introduction of cladding steel could significantly improve its ductility and low-cycle fatigue life; the fatigue life of the SC bimetallic steel is generally 30% similar to 60% higher compared with the corresponding CM steel, indicating its excellent low-cycle fatigue behaviour. The low-cycle fatigue life of the two steels could be well predicted by the strain-life relationship with adapted Basquin-Coffin-Manson model and Kuroda model, and the former is indicated superior to the latter in terms of the essential meaning and applicability.