Differential Scanning Calorimetry Study and Computer Modeling of b a Phase Transformation in Ti-6Al-4V Alloy

The relationship between heat-treatment parameters and microstructure in titanium alloys has so far been mainly studied empirically, using characterization techniques such as microscopy. Calculation and modeling of the kinetics of phase transformation have not yet been widely used for these alloys. Differential scanning calorimetry (DSC) has been widely used for the study of a variety of phase transformations. There has been much work done on the calculation and modeling of the kinetics of phase transformations for different systems based on the results from DSC study. In the present work, the kinetics of the transformation in a Ti-6Al-4V titanium alloy were studied using DSC, at continuous cooling conditions with constant cooling rates of 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C/min. The results from calorimetry were then used to trace and model the transformation kinetics in continuous cooling conditions. Based on suitably interpreted DSC results, continuous cooling–transformation (CCT) diagrams were calculated with lines of isotransformed fraction. The kinetics of transformation were modeled using the Johnson–Mehl–Avrami (JMA) theory and by applying the "concept of additivity." The JMA kinetic parameters were derived. Good agreement between the calculated and experimental transformed fractions is demonstrated. Using the derived kinetic parameters, the transformation in a Ti-6Al-4V alloy can be described for any cooling path and condition. An interpretation of the results from the point of view of activation energy for nucleation is also presented.

Gazing at Ground Zero: Tourism, Voyeurism and Spectacle

This essay uses the temporary viewing platform at the site of the former World Trade Center to explore our fascination with violence, conflict and disaster. It illustrates how discourses of voyeurism and authenticity promote a desire for sites of horror, and examines how that desire both disrupts and reinforces our prevailing interpretations of global politics. The viewing platform at Ground Zero was initially constructed to manage the thousands of people who traveled to New York in response to the shocking media images of 11 September. However, their desire to escape mediation and touch "the real" had the opposite effect - it transformed Ground Zero into a tourist attraction. Using Ground Zero as a starting point, this essay theorizes discourses of voyeurism and authenticity through the work of Baudrillard, Debord and Bauman in an effort to position the tourist as a significant political subject.