In situ neutron diffraction of the uniaxial tension test was used to study the effect of the surrounding matrix microstructure on the mechanical stability of retained austenite in highcarbon bearing steels. Comparing the samples with bainitic microstructures to those with martensitic ones it was found that the retained austenite in a bainitic matrix starts transforming into martensite at a lower strain compared to that within a martensitic matrix. On the other hand, the rate of transformation of the austenite was found to be higher within a martensitic microstructure. Crystal plasticity modeling was used to analyze the transformation phenomenon in these two microstructures and determine the effect of surrounding microstructure on elastic, plastic and transformation components of the strain. The results showed that the predominant difference in the deformation accumulated was from the transformation strain and the critical transformation driving force within the two microstructures. The retained austenite was more stable for identical loading conditions in case of martensitic matrix compared to the bainitic one.It was also observed that the initial volume fraction of retained austenite within the bainitic matrix would alter the onset of transformation to martensite but not the rate of transformation.

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Advances in stabilized finite element methods for bulk and sheet metal forming processes AIP Conf.Abstract. At The Timken Company, finite element modeling has been utilized successfully to design, improve and optimize metal forming processes in many areas from steel making processes for long products and tubes, and forming and shaping of discrete parts. It is very challenging to apply the finite element modeling to most incremental forming processes due to continuously changing contact conditions between workpiece and forming tools. This paper illustrates the use of different finite element formulations for the analysis of various incremental forming processes. Each finite element analysis (FEA) program has its own advantages and disadvantages in the areas of computational time and accuracy of results, so the selection of proper program to analyze a certain process is quite significant. Unique applications of FEA programs to assist the design of tooling and process parameters of several forming processes at The Timken Company are discussed. The analysis results of several cases were compared with available in-plant data and excellent agreement was observed.