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The aim of this work is to find out the most suitable method for detecting and analyzing accurately the formation conditions of secondary phases, particularly Sigma-phase (σ-phase) and Chiphase (χ-phase) in duplex stainless steels (UNS S32205 and UNS S32750). The microstructure was characterized after a solution annealing at 1080oC followed by an isothermal heating at 830oC for different time ranges, ranging from 1 minute to 9 hours, in order to enlighten the controversial point concerning the mechanism of χ-phase nucleation in relation with the σ-phase. Etched samples were observed using optical microscopy (MO), and scanning electron microscopy (FESEM) with a backscattered electron detector (BSE) was used on unetched samples. Compositional microanalysis (EDS) was carried out for identifying the different phases present in the steels. Sigma phase was easily observed using different etching procedures, whereas χ-phase was only clearly detected with FESEM-BSE on unetched samples. The compositional analyses showed that the molybdenum content in χphase almost doubles the content of this element in σ-phase, and as a result the kinetics of nucleation and growth were also found to be remarkably faster when the alloy content in the steel is higher. In addition, chromium nitrides and carbides were also observed to precipitate as a result of the heat treatments and, in the case of the chromium nitrides, they act as a favorable site for the nucleation of σphase and χ-phase.

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Previous processing studies have shown that constituents that are prosodically marked as focus lead to an activation of alternatives. We investigate the processing of constituents that are prosodically marked as contrastive topics. In German, contrastive topics are prosodically realized by prenuclear L∗+H accents. Our study tests (a) whether prenuclear accents (as opposed to nuclear accents) are able to activate contrastive alternatives, (b) whether they do this in the same way as constituents prosodically marked as focus with nuclear accents do, which is important for semantic modeling, and (c) whether the activation of alternatives is caused by pitch accent type (prenuclear L∗+H as contrastive accent vs. prenuclear L+H∗ as non-contrastive accent) or by differences in F0-excursion (related to prominence). We conducted two visual-world eye-tracking studies, in which German listeners heard declarative utterances (e.g., The swimmer wanted to put on flappers) and watched displays that depicted four printed words: one that was a contrastive alternative to the subject noun (e.g., diver), one that was non-contrastively related to it (e.g., sports), the object (e.g., flappers), which had to be clicked, and an unrelated distractor. Experiment 1 presented participants with two naturally produced intonation conditions, a broad focus control condition with a prenuclear L+H∗ accent on the subject and a contrastive topic condition with a prenuclear L∗+H accent. The results showed that participants fixated more on the contrastive alternative when the subject was produced with an L∗+H accent, with the same effect size and timing as reported for focus constituents. Experiment 2 resynthesized the stimuli so that peak height and F0-excursion were the same across intonation conditions. The effect was the same, but the time course was slightly later. Our results suggest that prenuclear L∗+H immediately leads to the activation of alternatives during online processing, and that the F0-excursion of the accent lends little. The results are discussed with regard to the processing of contrastive focus accents and theories of contrastive topic.