Abstract
To improve the shape memory effect (SME) of 304 austenitic steel effectively and efficiently, thermomechanical cycling, comprising deformation at room temperature and annealing, was applied. The influences of cycle number and annealing temperature on the SME and microstructures in 304 austenitic steel were investigated by light microscope (LM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The shape recovery ratio was remarkably improved from 16% to 40% after two thermomechanical cycles. The optimum annealing temperature was 833 K in the process of thermomechanical cycling. The improved SME by thermomechanical cycling was mainly related to stress-induced ε martensite rather than stress-induced α’ martensite. The reason is that thermomechanical cycling can not only promote the occurrence of the stress-induced γ→ε martensitic transformation, but also suppress the subsequently stress-induced ε→α′ transformation.
Highlights
Because of its good mechanical properties, corrosion resistance, and weldability, 304 austenitic steel is widely used in civil engineering applications [1]
Mangonon et al reported that such a repetition can occur in 304 austenitic steel when deformed at subzero temperatures and after subsequent annealing [16]
We investigate the effects of thermomechanical cycling comprising 13% tensile deformation at room temperature (RT) and subsequent annealing at different temperatures on the shape memory effect (SME) and microstructures of 304 austenitic steel, in order to investigate the aforementioned issues
Summary
Because of its good mechanical properties, corrosion resistance, and weldability, 304 austenitic steel is widely used in civil engineering applications [1]. Reported that, as a result of the stress-induced γ→ε martensitic transformation and its reverse transformation, a weak shape memory effect (SME) occurred in 304 austenitic steel [4,5]. A good SME could be obtained in FeMnSi-based alloys resulting from the stress-induced γ→ε martensitic transformation [6,7,8,9,10,11]. Considering the superior corrosion resistance and workability of 304 austenitic steel, it is significant to improve the SME resulting from the stress-induced γ→ε martensitic transformation in 304 austenitic steel. Mangonon et al reported that such a repetition can occur in 304 austenitic steel when deformed at subzero temperatures and after subsequent annealing [16]
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