Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays
We investigate the non uniform plastic deformation of a TWIP FeMnC steel by diffraction of high energy synchrotron X-rays. In particular, we observe the propagation of bands of plastic strain localisation. Debye-Scherrer rings are recorded in situ during tensile tests at two different strain rates. Discontinuous initial rings characteristic of unstrained polycristals with no texture become rapidly continuous after several percents of plastic strain due to strain gradients within the grains and a strong texture develops. The crystallographic dependence of the Young’s modulus is estimated and is consistent with the elastic anisotropy of a cubic crystal. A delay between the serrations on the macroscopic tensile curve and the stepwise variations of the diffracted peak’s position and width are consistent with propagating bands nucleating outside the X-ray beam. Slower and thinner bands are observed at the lowest strain rate. A tensile test interrupted to perform a few minute relaxation leads to a displacement of the nucleation site of the bands from one end to the middle of the gauge part.
B. Mishra, M. Ionescu and T. Chandra
J. P. Chateau-Cornu et al., "Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays", Materials Science Forum, Vols. 783-786, pp. 1105-1110, 2014