Abstract
This study investigated the tensile properties and deformation behavior of an aged Fe-26Mn-6Al-1C (mass%) alloy with a stacking fault energy of approximately 60 mJ·m−2. The results show that an ordered phase with a “short-range ordering” (SRO) structure formed after aging at 550°C for 10 h, further increasing the aging time to 48 h. Lamellar second-phase precipitates appeared at the austenitic grain boundaries. The aged sample at 550°C for 10 h exhibited an enhanced tensile strength (∼898 MPa) without notably sacrificing uniform elongation (∼46.3%), which was mainly attributed to the relatively high strain hardening in the entire plastic deformation due to the synergistic effects of planar slip, twinning-induced plasticity (TWIP), microband-induced plasticity (MBIP), and especially the formation of short-range ordering.
Highlights
IntroductionFe-Mn-Al-C steels have been extensively researched over the past several decades due to the high specific strength and stiffness of this material, which is a good trade-off between high ultimate tensile strength and good tensile ductility (Frommeyer and Brüx, 2006; Li et al, 2015; Klimova et al, 2017; Sarkar et al, 2019; Choi et al, 2020; Li et al, 2020) when compared with conventional high strength steels
After solution treatment at 1,100°C for 1 h, the grain size of γ was measured at around 130 μm with some amount of annealing twins (Figure 1A), and only γ phase peaks were detected by XRD patterns (Figure 2)
It has been reported that the coarse second-phase particles could be observed along the austenitic grain boundaries by optical microscopy for the Fe-(28–31.5)Mn(8.0–9.0)Al-(0.8–1.05)C alloys aged for 120–129 h (Hwang et al, 1993), which was different from the present short-time aged Fe26Mn-5.84Al-1.0C alloy
Summary
Fe-Mn-Al-C steels have been extensively researched over the past several decades due to the high specific strength and stiffness of this material, which is a good trade-off between high ultimate tensile strength and good tensile ductility (Frommeyer and Brüx, 2006; Li et al, 2015; Klimova et al, 2017; Sarkar et al, 2019; Choi et al, 2020; Li et al, 2020) when compared with conventional high strength steels. The addition of Al to high Mn austenitic steels reduces the weight of the automotive body due to its lower density and varies the deformation mechanisms of steels from either transformation-induced plasticity (TRIP) or twinning-induced plasticity (TWIP) (Grässel et al, 2000; Sohn et al, 2014; Yuan et al, 2015; Huang et al, 2017; Luo and Huang, 2018) to dislocation slip due to the increased stacking fault energy (SFE) (Frommeyer and Brüx, 2006; Li et al, 2015; Choi et al, 2020; Li et al, 2020). In the late 1970s, the (Fe,Mn)3A1C κ-carbide precipitates with an ordered L’l2
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