Potential Significance of Low Tempering Treatment in Improving the Mechanical Properties of a Cold‐Rolled and Intercritical Annealed Medium Mn Steel

Abstract

Herein, the effect of tempering at 200 °C for 20 min on the mechanical properties of a cold-rolled and intercritical annealed medium Mn steel is investigated in this study. This effect is mainly dependent on the original annealing condition. For the sample annealed at a relatively low temperature (660 °C), the austenite stability of this sample is further improved significantly after tempering. Thus, the transformation-induced plasticity (TRIP) effect is severely inhibited during deformation, which leads to a decrease in the properties of the sample. By contrast, for the sample possessing suitable austenite fraction (%30%) and heterostructure, that is, the sample annealed at 680 °C for 10 min, the simultaneously increased strength and ductility are significantly intrigued by tempering treatment. Electron probe microanalysis and 3D atom probe results reveal that C concentration in austenite is increased due to the C repartition during tempering, which leads to the persistent TRIP effect in a broad strain range during tensile deformation. In addition, the heterogeneous-deformation-induced stress of the heterostructured sample is found to be obviously intensified by tempering treatment. Thus, an excellent strength plastic synergistic effect with a product of ultimate tensile strength and total elongation of approximately 70 GPa% is obtained in the tempered sample.

Effect of Al Content on Inclusions in Fe‐15Mn‐xAl‐C Low‐Density Steel

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In recent years, Fe-Mn-Al-C low-density steel has been applied in important fields such as automobiles, ships, and aerospace, due to its excellent wear resistance, corrosion resistance, and lightweight. [1][2][3][4][5] Mn element has the effect of expanding the austenite zone, and its induced twinning effect is beneficial for hindering the propagation of cracks in the material, significantly improving the plasticity of the steel. [6] When the Al content in the steel increases by 1%, the density of the steel decreases by about 1.3%.

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