Super austenitic stainless steels are often welded using high Mo, Ni base filler metals to maintain the corrosion resistance of the weld. An important aspect of this processing is the weld metal dilution level, which will control the composition and resultant corrosion resistance of the weld. In addition, the distribution of alloying elements within the weld will also significantly affect the corrosion resistance. Dissimilar metal welds between a super austenitic stainless steel (AL-6XN) and two Ni base alloys (IN625 and IN622) were characterised with respect to their dilution levels and microsegregation patterns. Single pass welds were produced over the entire dilution range using the gas tungsten arc welding process. Microstructural characterisation of the welds was conducted using light optical microscopy, scanning electron microscopy, and quantitative image analysis. Bulk and local chemical compositions were obtained through electron probe microanalysis. The quantitative chemical information was used to determine the partition coefficients k of the elements in each dissimilar weld. The dilution level was found to decrease as the ratio of volumetric filler metal feedrate to net arc power increased. Reasons for this behaviour are discussed in terms of the distribution of power required to melt the filler metal and base metal. In addition, the segregation potential of Mo and Nb was observed to increase (i.e. their k values decreased) as the Fe content of the weld increased. This effect is attributed to the decreased solubility of Mo and Nb in austenite with increasing Fe additions. Since the Fe content of the weld is controlled by dilution, which in turn is controlled by the welding parameters, the welding parameters have an indirect influence on the segregation potential of Mo and Nb. The results of the present work provide practical insight for corrosion control of welds in super austenitic stainless steels.

This report documents a model to represent the true stress-strain, σ − , behavior of structural steel. It is based on combination of data from the NIST World Trade Center collapse investigation and many other evaluated literature sources. Unlike other models for stress-strain behavior of structural steel, such as the Eurocode 3 formulation [1], the model explicitly describes the time-dependent nature of the strength of steel at high temperature. For untested steels, it predicts the stress-strain behavior using only the measured room-temperature yield strength, S y. The relative deviation between the model of this report and the actual data for the steels is generally less than 25 %, and is always less than 50 %. On subset of eight steels, the model predicts the stress-strain behavior slightly better than the equally complicated Eurocode 3 model. For three literature structural steels, not analyzed as part of the model, the model of this report and the Eurocode 3 model predict stress-strain behavior with similar quality.

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A method has been developed that allows measurement of stress-strain curves for sheet metal being deformed in multiaxial tension. The strain state is imposed using a modification of the Marciniak in-plane biaxial stretching test. Resulting stresses are measured using a modified Xray diffraction (XRD) residual stress measurement system. This system is flexible enough to allow spatial mapping of in-plane stress and measurement of stresses at specific locations of interest on the sample, such as developing localizations. Results are presented correlating measurements on a thin strip of AA5182 with data from standard uniaxial tension test. Also presented are experimentally determined curves for this material in balanced biaxial tension in both the rolling and transverse directions.