Using metallurgical models, three steels were designed to obtain carbide-free bainitic structures in the as-rolled condition. Experimental castings were hot-rolled in a pilot mill and their austenite decomposition kinetics were measured using dilatometry. Tensile and Charpy impact properties were measured and the microstructures were characterised using X-ray diffractometry, optical and scannin...

A bainitic microstructure with fine ferrite plates (20 to 40 nm) in a matrix of high-carbon retained austenite, obtained by isothermal transformation at 200°C, was characterized with an energy-compensated optical position-sensitive three-dimensional atom probe. The average carbon concentration in the austenite was found to be 8.0±1.6 at.% and in the bainitic ferrite 1.1±0.7 at.%. The latter con...

Bainitic transformation at low transformation temperatures leads to a microstructure involving fine plates of bainitic ferrite and thin films of retained austenite. This microstructure has shown ultimate tensile strength of about 2.2 GPa, noticeable uniform elongation in the range of 5 to 30%, hardness values of about 600 to 670 HV and impact toughness in the range of 30 to 40 MPa m1/2. With ca...

the influence of aluminium on the microstructure of austempered ductile cast iron (adi) has been studied. anumber of irons of different compositions have been made by green sand casting and gravity die casting ofappropriate design to provide the experimental materials. austenitising was carried out at different temperaturesand holding times for a variety of experimental irons to achieve suffici...

the development of nano/ultrafine bainitic structure in aisi 52100 steel was the goal of this study. for this purpose,the aisi 52100 the specimens were austenitized at 1050 °c for 60 min followed by low-temperature austemperingtreatment at different temperatures and times. the austempered samples were characterized using field emissionscanning electron microscopy (fesem), x-ray diffraction (xrd...

Martensitic and bainitic steels are two types of widely used steels with excellent mechanical behaviors in automatic industry. It’s universally acknowledged that asquenched martensite possesses poor ductility and impact toughness, which should be tempered before putting into application. During tempering, as-quenched martensite changes from a hard and brittle microstructure to more ductile and ...

The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation between the nanobainitic microstructure and the fatigue limit is fundamental. Therefore, o...

The effect of tempering temperature, within the range of 400 to 700°C, on the microstructure and hardness of two super-bainitic steels, one as the control parent sample and the other with added Co & Al was investigated. Post-tempering examinations of the super-bainitic samples showed that low temperature tempering cycles (400–500°C) resulted in carbides formation, and some increases in the hard...

Seamless pipes are usually quenched and tempered after manufacture in order to obtain the desired properties. The possibility of avoiding this heat treatment is explored here, by designing steels which transform into an carbide free bainitic microstructure during cooling from the hot processing phase of the pipe. The cooling conditions studied are appropriate for the manufacturing process and c...

The influence of aluminium on the microstructure of austempered ductile cast iron (ADI) has been studied. A number of irons of different compositions have been made by green sand casting and gravity die casting of appropriate design to provide the experimental materials. Austenitising was carried out at different temperatures and holding times for a variety of experimental irons to achieve suff...