Effect of the Cold Rolling Reduction on the Microstructural Characteristics and Mechanical Behavior of a 0.06%C–17%Mn TRIP/TWIP Steel

Abstract

High Mn steels, alloyed with Si and Al, present large plasticity when deformed due to the TRIP/TWIP effect. The present work studies the microstructural evolution and its influence on the mechanical behavior of a steel containing 17%Mn and 0.06%C after cold rolling to 45 and 90% reduction and subsequent annealing at 700 °C for different times. The microstructural analysis is performed by X‐ray diffraction (XRD), scanning electron microscopy (SEM)‐electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). It is observed that cold reduction induces the formation of ϵ‐ and α′‐martensite. The material exhibits yield and tensile strength around 700 and 950 MPa, respectively, with a total elongation around 43% and a work hardening exponent of around 0.30 after 45% cold rolling and subsequent annealing and a yield and tensile strength of 750 and 950 MPa, respectively, with a total elongation of almost 50% when 90% cold rolling and subsequent annealing. The austenite texture contains brass, copper, and Goss components, while the α′‐ and ϵ‐martensite textures mainly consist of rotated cube and prismatic and pyramidal fibers, respectively.

Effect of rolling temperature on microstructure and mechanical properties of 18%Mn TWIP/TRIP steels

“…The values of UTS for the present steels processed by warm to hot rolling do not depend on the magnitude of work hardening (Fig. 7) similar to other studies on high-Mn TRIP/TWIP steels subjected to conventional rolling [17,34,53,54]. Therefore, the product of UTS×δ progressively increases from 35 to 95 GPa % with an increase in the rolling temperature from 773 K to 1373 K. It is worth noting that the Fe-18Mn-0.6C steel processed by warm rolling exhibits very high value of the yield strength up to 950 MPa provided by high dislocation density of 3.6×10 15 m −2 , which is comparable to that of (3.5-4.5)×10 15 m −2 observed in other high-Mn steel after large strain cold rolling [44].…”

“…The total elongation up to 90% and the ultimate tensile strength of about 1000 MPa can be attained, although the yield strength is approx. 300 MPa in such steels with recrystallized microstructure after conventional hot working or cold rolling followed by annealing [8,[15][16][17][18][19][20][21][22][23][24][25]. Commonly, an increase in the carbon content was favorable for the yield strength, ultimate tensile strength, and ductility [20,26,27], although even 0.8%C did not result in significant changes of the strength and plastic properties, namely, the ultimate tensile strength and yield strength of about 1000 and 300 MPa, respectively, and a total elongation of 80% were reported for Fe-17Mn-0.6C hot rolled at 1273 K [28].…”

The TRIP Effect and Its Application in Cold Formable Sheet Steels

“…The total elongation (TEL) versus ultimate tensile strength (UTS) diagram for steels utilizing the TRIP effect; representative mechanical properties of HMnS TRIP, Q&P TRIP, MMnS TRIP, Maraging TRIP, HEA TRIP from literature, LC TRIP from Autosteel website, and Meta‐stable ASS from standard EN10088‐2 …”

“…It has been reported that the TRIP effect in high‐manganese steels could result in superior mechanical properties, an excellent combination of high strength and good ductility, and high strain‐hardening capacity . There are mainly three high‐manganese steel groups, which have been intensively studied, namely Fe–Mn–Al–Si, Fe–Mn–C, and Fe–Mn–Al–C alloys. The chemical composition and corresponding SFE of some typical high‐manganese TRIP steels are listed in Table .…”

Formability of strong metastable Fe–15Cr–3Mn–3Ni–0.2C–0.1N austenitic TRIP/(TWIP) steel – A comparison of different base materials

“…However, another mechanism described as deformation-induced martensite formation could be observed as a result of rolling. Depending on the temperature, stress-or straininduced martensite can be formed, while stacking faults may also occur [24]. Indeed, Eskandari et al find that martensitic transformation can be minimized or completely suppressed at increased rolling temperatures [37].…”