Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions

Steels for bearings

The effect of morphology on the stability of retained austenite in a quenched and partitioned steel

Dual-phase (DP) steel is the flagship of advanced high-strength steels, which were the first among various candidate alloy systems to find application in weight-reduced automotive components. On the one hand, this is a metallurgical success story: Lean alloying and simple thermomechanical treatment enable use of less material to accomplish more performance while complying with demanding environmental and economic constraints. On the other hand, the enormous literature on DP steels demonstrates the immense complexity of microstructure physics in multiphase alloys: Roughly 50 years after the first reports on ferrite-martensite steels, there are still various open scientific questions. Fortunately, the last decades witnessed enormous advances in the development of enabling experimental and simulation techniques, significantly improving the understanding of DP steels. This review provides a detailed account of these improvements, focusing specifically on (a) microstructure evolution during processing, (b) exp...

An Overview of Dual-Phase Steels: Advances in Microstructure-Oriented Processing and Micromechanically Guided Design

Austenite stability and deformation behavior in a cold-rolled transformation-induced plasticity steel with medium manganese content

Experimental and numerical analysis on formation of stable austenite during the intercritical annealing of 5Mn steel

Microstructure of low alloy martensitic steel treated by quenching and partitioning (QP the fresh martensite is formed at the final quenching step and looks like ‘blocky’ type phase with size about 0.2–3 μm, and the retained austenite is mainly located on the packet boundary and initial austenite grain boundary. The measured volume fractions and carbon contents of these phases were slightly different from those predicted by the constrained paraequilibrium (CPE) model proposed by Speer, which was interpreted by the effects of the different grain sizes of the untransformed austenite after first quenching. Mechanical properties of steels processed by Q&P assume much higher strength and ductility than those processed by Q&T. It is concluded that Q&P process is a promising approach to control the multiphase structure with hard matrix and a ductile retained austenite, which gives an excellent combination of strength and ductility.

Characterization of microstructure obtained by quenching and partitioning process in low alloy martensitic steel

Microstructure and mechanical properties of medium manganese steel (Fe–0.2C–5Mn) processed by annealing at 650 °C with annealing time up to 12 h after accelerated cooling were studied. It was found that the martensite structure was gradually transformed into a superfine ferrite and austenite duplex structure by austenite reverted transformation during annealing process. The annealing heat treatment results in a large volume fraction of austenite (34%) and an excellent combination of ultimate tensile strength (∼1000 MPa) and total elongation (>40%) at room temperature. The ultrahigh tensile strength and improved ductility of present steel were mainly attributed to the enhanced phase transformation induced plasticity due to the large fractioned austenite.

Microstructure and mechanical properties of Fe–0.2C–5Mn steel processed by ART-annealing

Effect of intercritical annealing on the Lüders strains of medium Mn transformation-induced plasticity steels

The microstructural evolution of Fe–0.2C–5Mn steel during intercritical annealing with holding time for up to 144 hours was examined by TEM and STEM. It was demonstrated by TEM that the martensite lath structure gradually transformed into a lamellar ferrite and austenite duplex structure. The partitioning of manganese from ferrite to austenite was found by STEM. Typical Kurdjumov-Sachs orientation relationship between austenite lath and ferrite lath was observed by electron back scattered diffraction (EBSD). Based on the analysis of the austenite lath thckening behavior, it was proposed that the Mn-partitioning in austenite dominated the microstructure evolution of the ultrafine lamellar ferrite and austenite duplex structure during annealing process.

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Han Dong

Papers

Experimental and numerical analysis on formation of stable austenite during the intercritical annealing of 5Mn steel

Characterization of microstructure obtained by quenching and partitioning process in low alloy martensitic steel

Microstructure and mechanical properties of Fe–0.2C–5Mn steel processed by ART-annealing

Effect of intercritical annealing on the Lüders strains of medium Mn transformation-induced plasticity steels

Development of Ultrafine Lamellar Ferrite and Austenite Duplex Structure in 0.2C5Mn Steel during ART-annealing