Bainite

About: Bainite is a research topic. Over the lifetime, 9520 publications have been published within this topic receiving 145305 citations.

In situ synchrotron X-ray evaluation of strain-induced martensite in AISI 201 austenitic stainless steel during tensile testing

Abstract: The formation of strain-induced martensite in AISI 201 austenitic stainless steel was followed by in situ synchrotron X-ray diffraction during tensile testing. Real-time information allowed tracking microstructural changes related to the decomposition of metastable austenite (γ) into hcp-e-martensite and bcc-α′-martensite. Approximately 78% of α′-martensite was found after an equivalent strain of 0.39 and a corresponding elongation of 0.70 in the analyzed region. Microstructural characterization was carried out using electron backscatter diffraction and scanning electron microscopy. The work hardening behavior of each phase was evaluated and a strain partitioning between martensite and austenite was observed. Microstrain in austenite increased with strain whereas it remained nearly unchanged in α′-martensite during the experiment. At the end of the test, these two phases showed similar values of microstrain. The formation of martensite and the accumulation of defects in austenite are responsible for the overall work hardening behavior. Kernel average misorientation analyses showed very similar values of stored elastic energy in austenite and α’-martensite. Orientation relationships among the phases close to {111}γ//{0002}e//{011}α′ and γ// e// α′ were found.

Microstructure and mechanical characterization of friction stir welded high strength low alloy steels

Abstract: Friction stir welding (FSW) is a promising technique to join HSLA steels without the problems encountered during fusion based welding processes. In the present work, 3 mm thick HSLA plates were successfully welded using FSW. A tool made of tungsten-rhenium alloy was used in this work. The relationship between microstructure and tensile strength was studied under various welding conditions i.e. change in traverse speed (57–97 mm/min). The microstructure of the weld nugget revealed the presence of upper bainite and fine ferrite phases. The amount of upper bainite reduced with increase in traverse speed. EBSD images showed a reducing trend for grain size. The details of hardness, tensile strength and bending test were reported.

Interrelations of compositions, transformation kinetics, morphology, and mechanical properties of alloy steels

Abstract: The strong influence of the fine-scale microstructural features on mechanical properties has become increasingly evident during the past decade. This is particularly true for fracture toughness of quenched and tempered alloy steels. Large differences in microstructure can be produced by isothermal, rather than athermal, treatments in the bainite and upper martensite temperature ranges. The kinetics of transformation, as well as the kinds and volume fractions of transformation products can be varied o ver wide ranges by relatively small changes in chemical composition. The effects of the common alloying elements on transformation kinetics, both separately and in various combinations were determined experimentally. The synergistic effects of individual elements added as pairs of elements were not predictable from a knowledge of the effects of the individual elements. Isothermal treatments, coupled with variations in the kinds and amounts of alloying elements, produced different morphologies, compositions, and volume fractions of the transformation products. The effects of such microstructural differences on tensile properties, fracture toughness, and fatigue characteristics were evaluated. Beneficial effects were found, such as substantial increases in fracture toughness, with small changes in alloy content or with heat treatments that differed from those conventionally used.