Abstract
This study evaluates the role of thermomechanical processing and heat treatment on the microstructure and mechanical properties of a hot rolled, annealed, and aged Fe-18Mn-10Al-0.9C-5Ni (wt%) steel. The steel exhibited rapid age hardening kinetics when aged in the temperature range of 500–600 °C for up to 50 h, which has been shown in other work to be the result of B2 ordering in the ferrite and κ-carbide precipitation within the austenite matrix. The ultimate tensile strength increased from 1120 MPa in the annealed condition to 1230 MPa after 2 h of aging at 570 °C. Charpy V-notch toughness was evaluated at −40 °C in sub-sized specimens with a maximum in the annealed and quenched condition of 28.5 J in the L-T orientation.
Highlights
Steels in the Fe-Mn-Al-C alloy system continue to be of interest as high-strength, low-density alternatives to traditional structural and automotive steels
This study investigated the role of thermomechanical processing and heat treatment on the microstructural development and mechanical properties of a Fe-18Mn-10Al-0.9C-5Ni steel that was hot rolled, annealed, and aged for plate applications
Annealing time and temperature are a critical factor in mechanical property optimization in this alloy system
Summary
Steels in the Fe-Mn-Al-C alloy system continue to be of interest as high-strength, low-density alternatives to traditional structural and automotive steels. Austenitic based compositions have excellent combinations of both strength and ductility, which depends on the composition and heat treatment. Precipitation of κ-carbide in hot rolled and recrystallized Fe-30Mn-9Al-1Si-0.9C (in wt%) steel has been shown by Bartlett et al [8] to greatly increase strength from 950 MPa to 1160 MPa after aging for 60 h at 530 ◦ C. Cast and solution treated steels with nominal compositions in the range of Fe-30Mn-9Al-1Si-0.9C (in wt%) have shown exceptional room temperature Charpy V-notch (CVN) toughness of up to 200 J in the solution treated condition at 20 HRC. The loss of strain hardening and toughness during aging is the result of dislocation shearing of the κ-carbide and the corresponding glide plane softening effect and grain boundary precipitation of deleterious phases [9]
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