D.T. McDonald

Ti-6Al-4V Recycled from Machining Chips by Equal Channel Angular Pressing

Ti-6Al-4V machining chips have been recycled into fully dense material by a solid-state process based on equal channel angular pressing (ECAP). The as-recycled material possessed a refined microstructure and contained a series of oxide layers associated with the boundary of each machining chip. The chip boundaries were observed to dissolve into interstitial solid solution following static annealing. A series of static heat treatments within the temperature range 700 to 1000°C, for durations of between 1 and 20 hours, were performed. The effect of thermomechanical processing on microstructure and mechanical properties is discussed and compared to the as-recycled and commercially available materials.

Member roles and identities in online support groups: Perspectives from corpus and systemic functional linguistics

Online support groups (OSGs) are common sources of both health information and social support. To augment existing qualitative understandings of member roles and identities in OSGs, this article presents a corpus-based investigation of shifts in member lexicogrammatical and discourse-semantic choices in a bipolar disorder OSG. In total, 8.4 million words in 57,000 posts were transformed into a structured, grammatically annotated corpus and investigated using systemic functional linguistics (SFL) as a theoretical framework, focusing on interpersonal and experiential meanings. The findings of mood and transitivity analyses show marked differences between new and veteran members’ language choices over the course of membership in the OSG: particularly, in how veteran members provide advice, and in how new and veteran members ascribe and attribute bipolar disorder to both the self and others. Discussion addresses the affordances and limitations of corpus linguistics and SFL as strategies for providing quantitative support for key claims of earlier research in this field.

Effect of Equal Channel Angular Pressing on Lamellar Microstructures in Nickel Aluminum Bronze

A lamellar nickel aluminum bronze has been processed by equal channel angular pressing (ECAP) and its microstructure investigated. The orientation, spacing, and morphology of the lamellae after ECAP were observed to be dependent on the orientation of the lamellae before ECAP with respect to the shear plane. Two distinct microstructures were produced following a single ECAP pass. The most common type consisted of fragmented lamellae with a reduced lamellar spacing, inclined between >0 deg and <45 deg to the exit channel, and the second type comprised bent lamellae with an increased spacing and were inclined between >45 deg and <180 deg, with exceptions at 0/180 deg and 45 deg. A model describing the evolution of lamellar microstructures subjected to a single ECAP pass has been proposed.