Study of the decomposition behavior of retained austenite and the partitioning of alloying elements during tempering in CMnSiAl TRIP steels

Characteristic of retained austenite decomposition during tempering and its effect on impact toughness in SA508 Gr.3 steel

“…Small amount of carbides firstly precipitate from the RA during tempering, and then the depleted RA can transform into other microstructures. According to the results in literature [14], the carbon diffusivity at 400 C is much lower than at 650 C. As a results, the RA spend much more time for decomposition during tempering at 400 C than at 650 C.…”

Study of The Precipitation Behavior and Strengthening of Carbides during the Partition Process

“…Although the Si and Al elements in the spring steel can inhibit the precipitation of cementite in the Q&P process,E.P.Da Siva, D.De knijf, D.V.Edmods and Moor [5][6] all indicate that carbides precipitation in the partition period cannot be completely suppressed even in low carbon steels with relatively high Si and Al content, especially transition carbides [7][8].While precipitation of carbides and the diffusion of carbon in martensite into austenite are a competition mechanism.Carbides precipitation not only lead to the less content of retained austenite at room temperature, but also contribute to poor carbon in martensite,which can reduce comprehensive mechanical properties.As the second phase particle precipitation, the size of carbides will affect the mechanical properties of steel [9][10].The large size carbide particles formed in partition time are easy to cause stress concentration, reduce the plasticity and toughness,and it will result in serious brittle fracture.So,in addition to martensite,precipitation of carbides is also an important factor determining the mechanical properties of spring steel treated by Q&P process [11][12].…”

“…It mainly work in bending periodic, alternating torsion stress conditions, subjected to pull, pressure, shock, torsional fatigue, corrosion and other effects, sometimes bear high short-term sudden load. So the comprehensive mechanical properties of spring steel high requirements.The microstructure of martensite and retained austenite can be obtained by heat treatment of spring steel by Q&P process, and it has the advantages of both high strength and high plasticity in performance [1][2][3][4].Although the Si and Al elements in the spring steel can inhibit the precipitation of cementite in the Q&P process,E.P.Da Siva, D.De knijf, D.V.Edmods and Moor [5][6] all indicate that carbides precipitation in the partition period cannot be completely suppressed even in low carbon steels with relatively high Si and Al content, especially transition carbides [7][8].While precipitation of carbides and the diffusion of carbon in martensite into austenite are a competition mechanism.Carbides precipitation not only lead to the less content of retained austenite at room temperature, but also contribute to poor carbon in martensite,which can reduce comprehensive mechanical properties.As the second phase particle precipitation, the size of carbides will affect the mechanical properties of steel [9][10].The large size carbide particles formed in partition time are easy to cause stress concentration, reduce the plasticity and toughness,and it will result in serious brittle fracture.So,in addition to martensite,precipitation of carbides is also an important factor determining the mechanical properties of spring steel treated by Q&P process [11][12].There were no systemic study of precipitation of spring steel in the partition of carbides and its effects on the mechanical properties in the domestic and foreign literatures.The purpose of the present work was to explore the influence ofcarbides on mechanical properties by the statistics of carbides precipitation types, quantity and size distribution of spring steel after different Q&P processes,and calculate the contribution to strength.It is determined that In addition to the changes in mechanical properties caused by different tissue structures, the contribution of carbides precipitation strengthening is confirmed ,which can provide guidance for optimizing mechanical properties. …”

Effects of Phase Evolution on Mechanical Properties of Laser-Welded Ferritic Fe-Al-Mn-C Steel

“…To enable a prediction of the effect of the heat input on the microstructure and mechanical properties of joints in a 0.35 wt % C-3.5 wt % Mn-5.8 wt % Al lightweight steel, Sohn et al [10] evaluated the effect of the annealing temperature on the microstructural evolution and tensile properties of the steel. Choi et al [30] performed simulations of the kinetics and controlled solidification of similar steels while Park et al [31] proposed a tempering approach as a means of understanding the effects of heat treatments on such steels.…”