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

Abstract

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.

Improving the Mechanical Properties of Low‐Carbon Steel by In Situ Strain Aging

“…Two main factors contribute to the elongation of YPE: the Cottrell atmosphere and grain size. [ 27–30 ] As discussed earlier, the Cottrell atmospheres were further developed through the generation of dislocations and diffusion of interstitial atoms during the in situ strain aging process. The Cottrell atmosphere‐induced yield point phenomenon (YPP) exhibits an upper yield point due to strongly pinned dislocations and a lower yield point when the pinned dislocations break away, allowing dislocation movement at lower stress levels.…”

“…The Cottrell atmosphere‐induced yield point phenomenon (YPP) exhibits an upper yield point due to strongly pinned dislocations and a lower yield point when the pinned dislocations break away, allowing dislocation movement at lower stress levels. [ 27,28 ] Therefore, the dislocations generated and the additional formation of Cottrell atmospheres during the in situ strain aging process extended the YPE of the AP‐LC steel. Such an extension of the YPE demonstrates the additional formation of the Cottrell atmospheres during the in situ strain aging process.…”

Hot forming with a nonuniform temperature field using die partition cooling

“…As a result, the hot forming of high-strength steel has been widely used in automobile manufacturing; indeed, ultrahigh-strength steel components with tensile strengths in the range from 1500-2000 MPa can be manufactured by hot forming. Hot formed parts are widely used in the production of vehicle body structural parts such as anti-collision beams in doors, A-pillars, B-pillars and C-pillars [4,5]. With the development of science and technology, people have gradually obtained that the loads on automobile parts when the automobile is in service are not uniformly distributed.…”