Effect of retained austenite on the microstructure and mechanical properties of cold-rolled medium-manganese Q&P steel

Abstract

The effect of retained austenite stability on microstructure evolution and mechanical properties of a new cold-rolled medium-manganese steel (0.12C, 7.69Mn, 1.45Si, 2.76Al wt-%) under intercritical annealing Q&P process at different partitioning temperatures was investigated. The evolution of retained austenite was characterized and statistically analysed using SEM, TEM, EBSD, and XRD techniques. The results show that the stability of retained austenite depends to a large extent on the applied heat treatment and is mainly attributed to the retained austenite content and morphology, whose carbon content is not the main influence. More retained austenite content and the formation of heterogeneous austenite structures (granular, massive, lamellar) are observed at a partitioning temperature of 150°C. The retained austenite of different morphologies has different stabilities and can sustain the TRIP effect at different strain stages, obtaining the best comprehensive mechanical properties with 34.5% elongation and the product of tensile strength and elongation is up to 43.5 GPa•%.

Effect of annealing time on microstructure and mechanical properties of Fe–C–Mn–Al–Si steel

“…It has been found that retained austenite with different morphologies and degrees of stability can maintain the TRIP effect at different strain stages, thereby obtaining excellent mechanical properties. 5,6 Hu studied the microstructure and properties of 0.06C-5.5Mn steel at different annealing temperatures and annealing times. In the inter-critical annealing process, it is found that the reverse transformation of martensite to austenite, the austenite reversed by shows different stability, thereby improving plasticity and delaying necking.…”

Effects of different annealing time on microstructure and mechanical properties of lightweight Al-containing medium-Mn steel

“…The purpose of our development of medium manganese steel is to minimize the use of alloying elements without changing the overall properties of the steel, to achieve the effect of energy saving, emission reduction, and cost reduction of automotive steel. The results suggest that the retained austenite (γ) in medium manganese steels exhibits the transformation-induced plasticity (TRIP) effect, which is the primary cause of the excellent mechanical characteristics of these steels [7][8][9][10][11][12][13]. Therefore, one of the main challenges in developing medium manganese steels is the need to obtain a certain amount of metastable austenite.…”

The Impact of Tempering Temperature on Retained Austenite and Mechanical Properties of 1.2842 Tool Steel

“…Generally, an optimal amount of RA can bolster ductility and toughness, whereas an excess can impair the dimensional stability, strength, and wear resistance of steel components. Therefore, it is important to select proper heat treatment conditions for achieving optimal service life and mechanical properties [3][4][5][6].…”