The present paper gives a review of results of recent studies investigating the fundamentals of the martensitic and related phase tr-ansformations in Ni-A]. For the former case, the emphasis will be on the microstructure of martensite plates. The latter include the metastable Ni2A1 o-like and stable Ni5A13 bainitic phases. These phases will be discussed in view of their atomic structure, nuclea...

Neural network predictions suggested that the strength of a high strength steel weldmetal with 7 wt-% nickel and 0.5 wt-% manganese could be increased significantly at moderate expense to impact toughness by additions of carbon. Based on this, three experimental weldmetals were produced with carbon contents between 0.03 and 0.11 wt-%. Mechanical test results were in agreement with predictions. ...

Knowledge of carbon content in retained austenite (RA) with different neighbouring phases is essential to understand the chemical stability of RA, which is useful for microstructure tuning of transformation-induced plasticity (TRIP) steels. The present study investigates different morphologies and chemical compositions of RA by correlating electron backscattering diffraction, transmission elect...

Bainite has been obtained by heat treatment at temperatures as low as 125°C in a high carbon, high silicon steel. This has had the effect of greatly re® ning the microstructure, which is found to have a strength in excess of 2.5 GPa together with an ability to ̄ ow plastically before fracture. Such properties have never before been achieved with bainite. In this paper metallographic details are ...

Neural network predictions suggested that strength of a high strength steel weld metal with 7 wt. % nickel and 0.5 wt. % manganese could be increased significantly at moderate expense to impact toughness by additions of carbon. Based on this, three experimental weld metals were produced with carbon levels between 0.03 and 0.11 wt. %. Mechanical test results were in agreement with predictions. W...

Bainitic steels are now at the forefront of new and exciting developments in steel technology. This paper discusses how phase transformation theory is being exploited in the systematic design of every aspect of the new alloys, emphasising the immense influence that Professor Wayman has had on the development of the subject [1]. Technology of Bainitic Steels Gone are the days when industry could...

A combination of neural networks and genetic algorithms has been used to design a TRIP assisted steel in which the silicon concentration is kept low. In this context, the steel has a novel microstructure consisting of d ferrite dendrites and a residual phase which at high temperatures is austenite. This austenite can, with appropriate heat treatment, evolve into a mixture of bainitic ferrite an...

Recent work has shown that bainitic ferrite plates produced by transformation at low temperatures can be as thin as 20 nm with a hardness in excess of 650 HV30, tensile strengthy2.3 GPa and toughnessy30 MPa m. Because these properties rely on the fine scale of the microstructure, a study has been carried out in relation to the tempering resistance of steel over the temperature range 350 – 750uC...

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...

The development of ultrafine bainitic structure in AISI 431 stainless steel was the goal of this study. For this purpose, the AISI 431 specimens were austenitized at 1100 °C for 60 min followed by low-temperature austempering treatment at different temperatures and times. Austempered samples were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (X...