The Effects of Intercritical Annealing Temperature and Initial Microstructure on the Stability of Retained Austenite in a 0.1C-6Mn Steel

Abstract

The effects of the intercritical annealing temperature and initial microstructure on the stability of retained austenite were investigated for a 0.1C-6Mn (wt-%) steel. Medium-Mn transformation-induced plasticity (TRIP) steels exhibit a strong dependence of their mechanical properties on the variation of intercritical annealing temperature. This behavior is strongly linked to the amount and stability of the retained austenite. Thus, interrupted tensile tests were used to examine the effect of annealing temperature on the stabilization of the retained austenite. Detailed microstructural investigations were employed to elaborate the effects of its chemical and mechanical stabilization. Furthermore, the final microstructure was varied by applying the batch annealing step to an initial non-deformed and deformed microstructure respectively. Retained austenite stability along with resulting mechanical properties of the investigated medium-Mn TRIP steel was significantly influenced as the amount and morphology of the respective phases altered as a consequence of both initial microstructure and applied intercritical annealing temperature.

Effect of Manganese on the Structure-Properties Relationship of Cold Rolled AHSS Treated by a Quenching and Partitioning Process

“…This was linked to the presence of α' prim in the initial microstructure related to low chemical RA-stability. Therefore, in this case, RA could not contribute to the enhanced TRIP-effect, which is in correlation with results reported in literature [28][29][30].…”

Impact of Si and Al on Microstructural Evolution and Mechanical Properties of Lean Medium Manganese Quenching and Partitioning Steels

“…This is confirmed by a significant increase in k p values ( Figure 7 a), particularly in case of the samples containing α′ final (open symbols). As already reported in several studies, [ 31,32 ] this can be attributed to the pronouncedly declining chemical stabilization by lower C enrichment in austenite. As obvious from Figure 7a, achieving a k p value below 50 is of vital importance to sufficiently stabilize RA up to RT and consequently avoid the formation of α′ final .…”

On the Damage Behavior of a 0.1C6Mn Medium‐Mn Steel

“…It can be seen that the RA‐stability significantly decreased with increasing T IA (Figure ). As already reported by Steineder et al, this is due to a significant decrease in the chemical stabilization by lower C as well as Mn‐enrichment in the austenite and a decreasing mechanical stabilization due to substantial grain growth of the RA. Linking the RA‐stability to the mechanical properties presented in Figure and , it became evident that an intermediate RA‐stability is favorable to generate the best combination of UTS and TE.…”

“…As a result, ultimate tensile strengths (UTS) >800 MPa combined with total elongations (TE) up to 40% can be obtained for this steel grade. This can be achieved by the transformation of metastable RA into hard martensite during deformation by the TRansformation Induced Plasticity (TRIP) effect, which improves both strength and elongation of medium‐Mn steels …”

“…This can be achieved by the transformation of metastable RA into hard martensite during deformation by the TRansformation Induced Plasticity (TRIP) effect, which improves both strength and elongation of medium-Mn steels. [1][2][3] Most of the research work on medium-Mn steels conducted so far has been directed toward understanding the role of chemistry, [3][4][5] the microstructural evolution, [6][7][8][9] and the resulting mechanical properties determined by tensile testing. [3,[10][11][12][13] Since the manufacturing of complex body parts as well as the crash performance are requested properties for medium-Mn steels, the topic of damage behavior is of paramount interest for this steel group.…”