Investigation of Physical-Mechanical Properties and Structural Stability of the Nitrogen-Free and Nitrogen-Containing Austenitic Alloys of Fe-Cr-Mn System at Cryogenic Temperatures

摘要

Nitrogen effect on metastable state of Fe-Cr-Mn alloy at cryogenic temperature have been studied. Topograms were experimentally built showing distribution of mechanical characteristics at 77 K for the Fe-Cr-Mn and Fe-Cr-Mn-N system alloys (in the limits of 20-50% Mn and 0-15% Cr). Decreasing of maximal relative elongation, reduction and impact strength by 34, 23 and 50% respectively, was observed for the alloys doped with 0.15% N. With this, strength properties and stability of the γ-phase simultaneously increased. Area of maximal stability and impact strength broadens towards increasing of Mn and Cr content, as well. Nitrogen effect on decreasing of plasticity and impact strength properties in purely austenitic alloys at 77 K depends on Mn and Cr content. Obtained results allow us to plot the phase diagram of the investigated region of Fe-Cr-Mn system at cryogenic temperatures in quenched and tempered states before and after deformation and draw AB-line separating γ- and γ + δ+ σ -phase region at 77 K.