Influence of Temperature on Phase Transformation and Deformation Mechanisms of Cast CrMnNi-TRIP/TWIP Steel

Abstract

At different temperatures ranging from ‑60°C to 200°C a cast CrMnNi-TRIP steel was deformed by uniaxial tension. The resulting microstructure was investigated using XRD, EBSD and LOM. The correlation of the phase transformation with the deformation temperature was examined. Depending on temperature, a transition in the deformation mechanisms was observed. Starting with the generation of deformation bands, accompanied by martensitic phase transformation, followed by twinning, the deformation mechanism turned to conventional dislocation glide with raising temperature. Between -60°C and 20°C the TRIP (TRansformation Induced Plasticity)-effect is the dominating deformation mechanism, whereas between 20°C and 200°C the TWIP (Twinning induced plasticity) effect is observed. The geometrical arrangement of martensite within the microstructure is considered within this study. The amount of α'-martensite is mainly responsible for the hardening rate and the resulting mechanical properties.

Deformation and strain hardening behavior of powder metallurgical TRIP steel under quasi-static biaxial-planar loading

“…First of all, the SEM micrographs were taken in backscattered electron (BSE) contrast reveal clearly both the formation of deformation bands (DB) within the austenitic matrix as well as the '-nuclei formed inside the deformation bands. This is in good agreement with literature and uniaxial tests [26].…”

Temperature Depending Influence of the Martensite Formation on the Mechanical Properties of High‐Alloyed Cr‐Mn‐Ni As‐Cast Steels

“…In the temperature range between 60°C and 100°C Cr‐Mn‐Ni steels show a combined TRIP and TWIP effect. For temperatures above 100°C a dominant formation of twins in the austenite is shown for Cr‐Mn‐Ni steels 8. Therefore, high‐alloyed Cr‐Mn‐Ni steels show in dependence of the temperature a TRIP effect or a TWIP effect or both.…”

“…These steels show the martensitic γ→α´ transformation in the temperature range between ‐60°C and 60°C, which can proceed directly or indirectly with the participation of the ε martensite. The result is the γ→ε→α´ sequence 7, 8. The direct γ→α´ transformation was never observed outside of deformation bands.…”

“…This can be obtained from suitable experiments 5. For Cr‐Mn‐Ni steels different mechanisms for transformation of the austenite into martensite and twins are discussed 7, 8. These steels show the martensitic γ→α´ transformation in the temperature range between ‐60°C and 60°C, which can proceed directly or indirectly with the participation of the ε martensite.…”

Considerations in the Design of Formable Austenitic Stainless Steels Based on Deformation-Induced Processes

“…As mentioned earlier, this does not apply to highly stable austenitic steels in which the threshold SFEs for the α′-martensite formation may not be attained even at cryogenic temperatures [14]. The α′-martensite formation under extremely planar glide conditions commonly occurs at the intersections of planar glide features [29][30][31].…”