An investigation was carried out to determine the effect of rapid solidification on the weld metal microstructure of austenitic stainless steels and its implication on the ferrite constitution diagram. A wide variety of stainless steels were laser welded at different welding speeds and laser power levels. The results indicate that both weld pool cooling rate and the postsolidification solid state cooling rates have a profound effect on the microstructures. For the steels investigated, the microstructures ranged from duplex austenite (7") + ferrite (6) to fully austenitic or fully ferritic. These microstructures were found to be sensitive to both cooling rates and composition. The observed results are rationalized based on rapid solidification theory. Observations of this investigation indicate that solidification rates and postsolidification cooling rates have a profound effect on the observed microstructures, thus making it impossible to predict the microstructures of rapidly cooled weld metal from the conventional constitution diagrams. The influence of the observations made in this investigation on the Schaeffler diagram is demonstrated and possible corrections to the constitution diagram incorporating the cooling rate effects are proposed.

This note considers a method, recently described by Dykstra, for augmenting existing data in response surface experiments. Examples are given to show how this relatively simple approach can be usefully applied, not only to design repair problems, but to situations in which the experimenter, after reviewing his initial results, decides to change his region of interest, his model, or both. KEY WORDSDesign Augmentation Design Repair D-optimality Response Surface P-1 Linear Model Polynomial Regression Region of Interest (Note: This note, which might alternatively be titled '(Augmentation of a Note by Dykstra,"was reduced from a longer paper which was to have been published in this issue. The recent publication of Dykstra's note [5] makes much of our original paper redundant.In fact, the problem, the design criterion, and the method of design augmentation are essentially the same. Therefore, we have shortened our original paper into the present note, the main purpose of which is simply to illustrate this design augmentation method with a wider range of examples.)

No abstract

No abstract

No abstract