Microstructure and properties have been studied for high strength steel weld metals with variations in carbon, manganese and nickel. Based on neural network modelling, experimental welds were made using shielded metal arc welding with manganese at 0.5 or 2.0 wt. % and nickel at 7 or 9 wt. %. Additional welds were made where carbon was varied between 0.03 and 0.11 wt. %. Generally there was very...

A theory is developed for the evolution of bainite as a function of time, temperature, chemical composition and austenite grain size. The model takes into account the details of the mechanism of transformation, including the fact that nucleation begins at the austenite grain surfaces, and that the growth of a sheaf occurs by the repeated nucleation of small platelets. Predictions made using the...

There is a novel steel invented in which the structure consists of extremely fine platelets of bainitic ferrite dispersed in a matrix of carbon enriched retained austenite. The resulting large density of interfaces makes the alloy very strong in its transformed condition. The authors report the first fatigue tests on this system, by measuring the life of parallel gauged samples tested using cyc...

High silicon (>1.5%) steels with different compositions were isothermally transformed to bainite at 220 and 250 ◦C to produce what is often referred to as nanostructured bainite. Interrupted tensile tests were carried out and the retained austenite was measured as a function of strain. Results were correlated with tensile ductility. The role of retained austenite stability is remarkably underli...

A PM approach is investigated in the context of extremely fine low temperature bainitic steels with a reasonable combination of ultimate tensile strength and uniform elongation. The strategy consists of three steps. First, ball milling is used for mechanical alloying and to create a large density of interfaces prior to sintering. In the second step, spark plasma sintering is used as a rapid con...

Strong steels also have to be tough and hence rely on fine microstructures such as bainite or martensite, produced commercially by continuous cooling transformation. Depending on the detailed requirements, the steel-design process may explicitly require other higher temperature phases to be absent in the final microstructure. Such a procedure can be made easier by the availability of a good met...

This work is to the best of my knowledge original, except where acknowledgements and references are made to previous work. Neither this, nor any substantially similar dissertation has been or is being submitted for any other degree, diploma or other qualification at any other university. This dissertation does not exceed 60,000 words in length. Abstract iii DFT Pak, Jun Hak 20080959 Coalesced s...

Herein, the diffusion and distribution of hydrogen (H) atoms in ferrite bainite contained an X80 pipeline steel is studied by both scanning Kelvin probe force microscopy finite-element modeling. The effect metallurgical microphases on H-atom accumulation analyzed. It showed results that H-charging elevates electrochemical dissolution activity steel, as indicated increased Volta potential thus d...