Effect of a New Prestrain, Intercritical Annealing, Quenching, and Partitioning Process on the Microstructure and Mechanical Properties of Medium‐Manganese Steels

Abstract

Simultaneously, the benefits of the traditional quenching and partitioning (Q&P) process (carbon distribution) and the austenite reverse transformation (ART) process (manganese diffusion) are combined to apply the Q&P process to the production of medium-manganese steels. [2][3][4] The elements C and Mn are broken down from ferrite/martensite and stabilized in austenite during reverse phase transformation. the microstructure of medium manganese steels, therefore, consists of a two-or three-phase microstructure of ultrafine grain ferrite, substable austenite, and/or fresh martensite (from austenite transformation). [5] However, the amount and stability of retained austenite are the most important elements influencing the mechanical characteristics of medium-manganese steels. Furthermore, the effects of chemical composition, [6] morphology, [7] grain size, [6] surrounding phases, [8] grain orientation, [9] and strain distribution between phases on retained austenite must be taken into account. At the same time, creating automobile components is a complicated process that involves many stretching, bending, and forming processes to finish. [10] Because these forming processes are similar to prestraining the sheet to varying degrees, studying the effects of prestrain on the microstructure and properties of the sheet can serve as a guide to the actual manufacture of the part. In recent years, studies on the prestrain of low-alloy high-strength duplex steels under unidirectional tensile stress have been published. The unidirectional stretching process pre-strain was used by Qiao, [11] with different sizes of prestrain (0%, 5%, 10%, and 15%) for DP780 duplex steel. The yield strength and tensile strength both rose when the prestrain increased, although the change in tensile strength was less. The mechanical properties and hardening behavior of transformation induced plasticity (TRIP) steels under different prestrain were studied by Hu. [12] As the tensile prestrain rose, the material's work-hardening capability was found to be significantly reduced. The prestretching, cupping, and reaming tests on high-strength steel DH780 were carried out by Liu. [13] It was discovered that when the prestrain rose, the retained austenite content steadily reduced, the yield strength and tensile strength both

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

“…The specimen's local stresses are subsequently transmitted to the ferrite and retained austenite, resulting in a relative reduction in the work-hardening rate. As a result, the microstructure undergoes fluctuating work-hardening rates [36]. The SIV stage is caused by the depletion or over-stabilization of retained austenite, which results in stress concentration in the microstructure and, eventually, plastic failure [19].…”