Neural networks are now a prominent feature of materials science with rapid progress in all sectors of the subject. It is premature, however, to claim that the method is established. There are genuine difficulties caused by the often incomplete exploration and publication of models. The assessment presented here is an attempt to compile a loose set of guidelines for maximising the impact of any models that are created, in order to encourage thoroughness in publication to a point where the work can be independently verified.

The martensite start and bainite start temperatures have been determined in reheated, high strength weld deposits, with each result associated with 95% coincidence limits. This helped define isothermal transformation temperatures where bainite can be obtained without the risk of unintentional transformation to martensite. It has been demonstrated, therefore, that coalesced bainite, which is detrimental to mechanical properties, can be generated isothermally without the possibility of confusion with autotempered martensite.

An experiment is presented which succeeds for the first time in stimulating the formation of coarse plates of bainite by the coalescence of identically oriented individual platelets. Transformation under the influence of a tensile stress dramatically promotes the formation of the coalesced bainite by increasing the probability of growing parallel platelets in close proximity. Whereas the coarse plates are detrimental to toughness, the result serves to validate the mechanism of coalescence which has been discussed extensively in the literature.Key words: Coalesced bainite, mechanism of coalescence, stress affected transformation, bimodal plate sizeIt is now known that in appropriate circumstances, thin-platelets of martensite or bainite can coalesce to produce much coarser plates that are detrimental to mechanical properties [1,2]; the subject has been reviewed [3]. The consequences of this coarser microstructure with a bimodal distribution of plate sizes, on toughness, continue to be revealed since the original work [4]; some recent studies on strong steels include [5][6][7][8][9][10]. One of the criteria necessary to obtain such coalescence is that the driving force for transformation must exceed the increase in strain energy associated with the coalescence process, and another that the platelets that combine must form on parallel habit planes

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Coarse crystals of martensite can form by the coalescence of thin individual platelets of martensite under appropriate circumstances. Although these coarse grains are essentially single crystals, there exist significant orientation gradients across their dimensions. It is demonstrated that these gradients arise because of the plasticity induced in austenite due to the transformation strain associated with martensite growth. The resulting localised change in austenite orientation is then inherited by the new martensite growth, which consumes the deformed austenite.