The possibility of producing bainite at low temperatures by suppressing transformation using substitutional solutes has been investigated, as an alternative to using large carbon concentrations to achieve the same purpose. It is found that although transformation temperatures can indeed be suppressed in this way, the difference between the bainite and martensite start temperatures diminishes. T...

structural steels with very high strength levels are often referred to as ultrahigh-strength steels (uhss). the usage of uhss has been extensively studied in aerospace industries and offshore platforms. in this study, medium carbon low alloy steel (ams6305) was thermomechanicaly treated to obtain an ultra-high strength bainitic steel for aircraft engine compressor disk. a novel themomechanical ...

During the course of our research on the quantitative design of steels [1,2], an exciting discovery was made, in which carbide–free bainite was obtained by transformation at incredibly low temperatures, as low as 125 ◦C [3]. To put this into context, the random jump distance of an iron atom at that temperature is only 10 m over a period of three weeks. The consequence of the low transformation–...

New developments with bainite have resulted in a steel with an ultimate tensile strength of 2500 MPa, a hardness of 600-670 HV and a toughness in excess of 30-40 MPa m [1]. The novel microstructure is generated in a high carbon (0.98 wt.%) high silicon (1.46 wt.%) steel austenitized for 15 min. at 1000 oC, and then isothermally transformed at temperatures of ∼200 oC. Iron does not diffuse durin...

We investigated the effects of the additions of Zr and other alloying elements on the mechanical properties and microstructure in Cr-Mo plastic mold steels. The addition of alloying elements changed the microstructure of the normalized samples from the upper bainite to lower bainite due to the increased hardenability. The tempering temperature influenced the strength and hardness values, especi...

Steels with a mixed microstructure of allotriomorphic ferrite, bainitic ferrite, retained austenite and martensite have potentially good combinations of high strength and formability. This work describes a kinetic theory for the formation of bainite in steels where the precipitation of carbides is suppressed. The theory is based on the mechanism of transformation. It includes, for example, a nu...

Several experimental techniques are used for phase identification and microstructure characterization of austempered vermicular cast irons (XRD, SEM, TEM and Mössbauer spectroscopy). Acicular structures were found to be composed by ferrite and austenite with average sizes compatible with those reported for bainitic ferrite in steels. An assessment of the free energy change involved in the auste...

By using an iron alloy that transforms slowly to bainite at a low temperature, it has been possible to study the development of the upper bainite under the influence of exceptionally large stresses, which are nevertheless below the yield strength of the parent austenite. It is found that a uniaxial stress whose magnitude is below the elastic limit, strongly favours the growth of compliant varia...

Shielded metal arc welding and submerged arc welding were used to prepare experimental weld metals with variations in nickel, manganese and carbon contents. The weld metals contained Ni between 6.6 and 10.5 wt. %, Mn between 0.5 and 2.0 wt. % while carbon was varied between 0.03 and 0.11 wt. %. Mechanical properties were found to be sensitive to alloying content. However once the optimum level ...