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Yield Point Elongation and Localized Deformation Bands in 22MnB5 Steel at Room Temperature



22MnB5 steel shows a yield point elongation (YPE) of ∼0.5% at room temperature. Uniaxial tensile tests of 22MnB5 steel specimens were performed in a quasi-static strain rate range from 3.33 × 10−5 s−1 to 3.33 × 10−3 s−1 with the aid of digital image correlation (DIC) technique to investigate the deformation behavior of 22MnB5 steel in a small strain range from 0 to ∼0.02. The evolutions of full fields of strain and strain rate on the 22MnB5 steel specimens were obtained. Discontinuously propagating localized deformation bands (LDBs) were observed before, during and beyond YPE, which are known as Type B Portevin-Le Chatelier (PLC) bands resulting in serrations on stress strain curves and they are not Luders bands unexpectedly. The peak strain rates in the LDBs before the YPE is relatively small, and during the YPE, the strain rate in the LDBs increases to ∼2 times of the applied nominal strain rate, which is explained by micro- and macro-plastic deformation mechanism.