Yield strength insensitivity in a dual-phase high entropy alloy after prolonged high temperature annealing

Recent studies of FeMnCoCr-based high entropy alloys have demonstrated uncommon deformation behaviors such as transformation-induced plasticity, which were largely believed to be restricted to select families of steels. Coupled with the potential for entropy stabilization of high symmetry phases at high temperatures, this system represents a promising class of materials for structural applications in extreme environments. Yet, transformation-induced plasticity mechanisms are notably sensitive to microstructure parameters and the literature offers examples of deleterious decomposition of high entropy alloys under heat treatment, which raises concerns of resiliency in mechanical performance. Here, we evaluate the evolution of microstructure and mechanical properties of a FeMnCoCr high entropy alloy after prolonged heat treatment at high temperature. Microstructures are found to retain their characteristic austenite/martensite features, with parent face-centered cubic grains partitioned by hexagonal close-packed laths after heat treatment at 1200 C for up to 48 hours. Results of mechanical testing reveal an unusual insensitivity of this alloy to grain growth-induced weakening effects. Namely, the yield strengths of FeMnCoCr samples are observed to remain constant across all heat treatment conditions, despite a near four-fold increase in the grain size. Close examination of post-heat treatment microstructures reveals a dramatic decrease in the inter-lath spacing at longer durations, which segments parent austenite grains. This crystal partitioning counteracts conventional grain growth-induced weakening by introducing additional barriers for dislocation pile-up. These results offer new insights into the mechanical resiliency of this transformation-induced plasticity high entropy alloy under prolonged high temperature heat treatment

The Properties and Gaseous Environments of Powerful Classical Double Radio Galaxies

The properties of a sample of 31 very powerful classical double radio galaxies with redshifts between zero and 1.8 are studied. The source velocities, beam powers, ambient gas densities, total lifetimes, and total outflow energies are presented and discussed. The rate of growth of each side of each source were obtained using a spectral aging analysis. The beam power and ambient gas density were obtained by applying the strong shock jump conditions to the ends of each side of the source. The total outflow lifetime was obtained by applying the power-law relationship between the beam power and the total source lifetime derived elsewhere for sources of this type, and the total outflow energy was obtained by combining the beam power and the total source lifetime. Composite profiles were constructed by combining results obtained from each side of each source. The composite profiles indicate that the ambient gas density falls with distance from the central engine. The source velocities, beam powers, total lifetimes, and total energies seem to be independent of radio source size. This is consistent with the standard model in which each source grows at a roughly constant rate during which time the central engine puts out a roughly constant beam power. The fact that the total source lifetimes and energies are independent of radio source size indicates that the sources are being sampled at random times during their lifetimes.Comment: 7 pages, 5 figures, to appear in "Extragalactic Jets: Theory and Observation from Radio to Gamma Ray", eds. T. A. Rector and D. S. De Young, ASP conference series, Replaced version has minor textual correction

Deformation Mechanisms in High Entropy Alloys: A Minireview of Short-Range Order Effects

The complex atomic scale structure of high entropy alloys presents new opportunities to expand the deformation theories of mechanical metallurgy. In this regard, solute-defect interactions have emerged as critical piece in elucidating the operation of deformation mechanisms. While notable progress has been made in understanding solute-defect interactions for random solute arrangements, recent interest in high entropy alloys with short-range order adds a new layer of structural complexity for which a cohesive picture has yet to emerge. To this end, this minireview synthesizes the current understanding of short-range order effects on defect behavior through an examination of the key recent literature. This analysis centers on the nanoscale metallurgy of deformation mechanisms, with the order-induced changes to the relevant defect energy landscapes serving as a touchstone for discussion. The topics reviewed include dislocation-mediated strengthening, twinning and phase transformation-based mechanisms, and vacancy-mediated processes. This minireview concludes with remarks on current challenges and opportunities for future efforts

Better Ways to Work: HVAC management, repair and maintenance in the mid-tier commercial office sector

This is the first piece of work from the Better Ways to Work project. It presents the results of the largest national survey of facilities managers, HVAC contractors and associated design and systems specialists undertaken to date

Light-activated modulation and coupling in integrated polymer-liquid crystal systems

We explore the transfer of an incident light pattern onto the liquid crystal (LC) bulk in a photorefractive cell through an integrated photoconducting layer that modulates the electric field applied to the device. The electrical properties and the strength of modulation are investigated as a function of the incident light intensity as well as the frequency and amplitude of the applied voltage, for two LCs with very different electrical conductivity. A simplified electrical model of the cell is proposed, demonstrating that the LC conductivity is a key factor determining the beam-coupling strength

The most powerful form of activism is just the way you live : grassroots intentional communities and the sustainability of everyday practice

University of Technology Sydney. Institute for Sustainable Futures.Changing household consumption patterns may be the fastest pathway for reducing the currently unsustainable levels of resource consumption in the developed world. Between 50% and 80% of global land, water and material consumption and greenhouse gas emissions can ultimately be traced to household consumption, contributing substantially to environmental degradation. Changing household consumption practices therefore presents an opportunity to significantly reduce this negative environmental impact. This thesis has explored ‘intentionally sustainable communities’, such as ecovillages and cohousing communities, as sites where significant changes to household consumption are occurring. These communities are niche sites of grassroots innovation; crucibles in which new arrangements of potentially innovative and sustainable household practices are formed that may (or may not) be usefully transferred to mainstream households. This research examines the extent to which these intentionally sustainable communities have reduced their environmental impacts. It then explores the environmentally beneficial household consumption practices that have been established and sustained, the role of the intentionally sustainable community in enabling members to change their practices, and the potential for these communities to have wider influence. A mixed method approach was adopted, first undertaking a systematic literature review of ecological and carbon footprint studies of intentional communities globally. Second, two Australian case study communities; a rural land sharing cooperative (Bundagen), and an urban cohousing community (Murundaka), explored the practices and elements of practice that residents perceived as significant for their everyday sustainability. Finally, the potential for Murundaka to influence household consumption practices on a wider scale was considered. The systematic review found strong but limited evidence that many intentional communities are achieving substantial reductions in environmental footprints. Empirical insights from the case studies revealed that a broad range of community-led interventions across many domains of practice were improving household sustainability in the communities. Key elements discussed include explicit and shared meanings from creating a community vision, the impacts of shared spaces, infrastructures and resources, and the role of community dynamics in circulating competences through effective social learning. The research highlights the key role played by nonmainstream practices such as the intentional, resident-driven creation of community and community-scale governance. These practices enable community members to act as both policy makers and practitioners, with greater scope and reflexivity to intervene in the systems of practice which shape their daily lives. Finally, pathways through which intentionally sustainable communities may be able to influence the practices of wider society were discussed, through an exploration of the influence of Murundaka on its broader community