Microstructure evolution and impact toughness measurement on a coarse grained heat affected zone (CGHAZ) of Q890steel have been investigated in this study by Gleeble 1 500 simulation technique. The results indicate that a relevant mediate energy input is recommended for welding of Q890 steel, according to a fact that an impact energy as high as 83 J is attained in the CGHAZ with t 8/5 of 20 s. It is related to the cumulative contribution of prior-phase bainitic ferrite separated martensite comprises interlocking structure of laths that can promote a sufficient subdivision of the block and finer effective grain size and the highest density of high angle boundaries. Higher heat input can result in brittle fracture in the CGHAZ since the stress concentration and triaxiality of the neighboring matrix are increased by the hard phase particles such as M-A constituents.KEY WORDS: microstructure; M-A constituents; impact toughness; electron backscattered diffraction (EBSD).

The effect of cold deformation on microstructure and mechanical properties of a Fe–20Mn–19Cr–0.5C–0.6N high nitrogen austenitic steel has been studied. Microstructural observations show that the low cold deformation is fully dominated by the dislocation structures, namely, pile‐ups, Taylor lattice, and dislocation cells. With further cold deformation, the effect of twinning induced plasticity and grains fragmentation play an important role during cold deformation process. At critical cold deformation reduction range of 26–36%, the microstructural transitions by dislocation planar slip and multiplication gradually transits to twinning. For mechanical properties, with the increase of cold deformation reduction, the yield strength increases from 0.52 to 1.60 GPa, being increased by three times. The flow stress–strain model of the solution‐treated specimen can be described as . In addition, the strength‐elongation product and the cold deformation reduction present a linear relationship with a correlation coefficient of −0.27 to estimate the variation rate of the strength‐elongation product during cold deformation.

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