Cold Work Hardening of High‐Strength Austenitic Steels

Abstract

Mechanisms of cold work hardening in three austenitic steels containing (mass%) 12Mn and 1.2C (Hadfield steel denoted as C1.2); 21Cr, 23Mn, 2Ni and 0.9N (Böhler steel P‐560 denoted as N0.9); 18Cr, 18Mn, 0.345C, 0.615N (CARNIT steel denoted as CN0.96) were studied using mechanical tension tests and TEM studies of substructure formed in the course of plastic deformation. Hadfield steel C1.2 reveals the smallest yield and ultimate stresses and elongation but the highest cold work hardening. Similar yield and ultimate stresses were obtained for steels N0.9 and CN0.96 with a higher elongation and cold work hardening for the latter. The analysis of TEM results leads to the following conclusions: Cold work hardening of the carbon steel C1.2 is mainly due to intensive twinning with rather thick twins. Localized planar slip is a feature of the substructure in the nitrogen steel N0.9 and carbon+nitrogen steel CN0.96 at strains up to 10 %, whereas twinning is involved in deformation at strains in the range of 10 to 50%. The strain‐induced ∊ martensite is rarely observed in both of these steels at strains above 30 %. The substructure and cold work hardening are discussed in terms of stacking fault energy, short‐range atomic order and binding between interstitial atoms and dislocations.

Hydrogen environment embrittlement of stable austenitic steels

“…It is known that under tensile strain Hadfield steel undergoes work hardening as a result of twin formation. Intensive twinning was found to occur already at low strains of 10% which corresponds to the range of reported stacking fault energies between 23 and 52 mJ/m 2 [8,51]. Formation of a 0 or 3-martensite does not occur even at high strains.…”

The influence of the nitrogen/nickel‐ratio on the cyclic behavior of austenitic high strength steels with twinning‐induced plasticity and transformation‐induced plasticity effects

“…The mechanical and chemical properties can be adjusted by further alloying elements like molybdenum and nitrogen as well as by cold-working [4,5]. Thus chromiummanganese-based austenitic high-nitrogen steels with up to 1 wt.% nitrogen were developed providing high strength and ductility [6][7][8].…”

Austenitic high interstitial steels vs. CoCrMo – Comparison of fatigue behavior

“…C and N are interstitial alloying elements and stabilize the austenitic phase. However, solid solution hardening by means of C and N is known to be more efficient than cold work hardening [10][11][12]. Another way to increase the solubility of N in the melt is adjusting the production methods [13].…”