Enhancement of properties in cast Mg-Y-Zn rod processed by severe plastic deformation

Ternary Mg-Y-Zn alloys have attracted considerable attention from researchers due to their excellent mechanical properties and unique microstructures, particularly from the presence of long-period stacking-order (LPSO) phases. Microstructural variations and the resulting mechanical properties can be affected by various processing routes, particularly those involving severe plastic deformation of a cast billet. The approach used in this work was based on subjecting cast Mg92Y4Zn4 (composition in wt%) billet to severe plastic deformation by three different routes, namely equal channel angular pressing (ECAP), high pressure torsion (HPT) and ECAP followed by HPT, with the aim of refining the microstructure and improving mechanical properties. Samples processed by ECAP were annealed by post-processing and tested in compression and tension. The effect of the processing route and the process parameters on the microstructure and the hardness of the Mg-Y-Zn alloy is reported. An overall positive effect of annealing treatment on the mechanical properties of ECAP-processed alloy is demonstrated. © 2014 Elsevier B.V.

Accelerated stem cell attachment to ultrafine grained titanium

Commercial purity titanium with an average grain size in the low sub-micron range was produced by equal channel angular pressing (ECAP). Attachment of human bone marrow-derived mesenchymal stem cells (hMSCs) to the surface of conventional coarse grained and ECAP-modified titanium was studied. It was demonstrated that the attachment and spreading of hMSCs in the initial stages (up to 24h) of culture was enhanced by grain refinement. Surface characterization by a range of techniques showed that the main factor responsible for the observed acceleration of hMSC attachment and spreading on titanium due to grain refinement in the bulk is the attendant changes in surface topography on the nanoscale. These results indicate that, in addition to its superior mechanical properties, ECAP-modified titanium possesses improved biocompatibility, which makes it to a potent candidate for applications in medical implants.

Influence of backpressure during ECAP on the monotonic and cyclic deformation behavior of AA5754 and Cu99.5

Ultrafine-grained (UFG) metals produced by equal channel angular pressing (ECAP) exhibit outstanding mechanical properties. They show high strength under monotonic loading as well as strongly enhanced fatigue lives in the Wöhler S-N-plot compared to their coarse grained (CG) counterparts. It could be shown that the fatigue lives can be significantly enhanced further by applying backpressure during ECAP. Besides the positive effect of backpressure on the processability of hard to deform materials via ECAP, the hydrostatic stress induced by backpressure also influences the mechanical properties under monotonic and cyclic loading. Therefore the influence of backpressure on ECAPed Cu99.5 and on the ECAPed aluminum alloy AA5754 was investigated. It is shown that backpressure has no effect on the hardness and grain size in Cu99.5 but changes the grain boundary misorientation to higher fractions of low angle grain boundaries. Also the temperature dependency of the yield strength as well as the hardening behavior under monotonic compression is affected. The cyclic deformation behavior of Cu99.5 is not strongly influenced by backpressure, but the mean stress level changes drastically. The fatigue life increases with the application of backpressure at low plastic amplitudes due to a change in the crack initiation and propagation. Aim of this work is the investigation of the influence of backpressure during equal channel angular pressing (ECAP) on the mechanical properties under monotonic and cyclic loading. Therefore we performed hardness measurements, compression, and fatigue tests on ECAPed Cu99.5 and AA5754. The results are discussed in terms of microstructure and relevant deformation and damage mechanisms.

Texture evolution and grain refinement of ultrafine-grained copper during micro-extrusion

Samples of oxygen-free high conductivity (OFHC) coarse-grained (CG) and ultrafine-grained (UFG) copper were micro-extruded to an equivalent strain of 2.8 in one pass at room temperature. Samples of the OFHC copper were annealed at 650C for 2 h to produce CG copper. Some samples were subsequently processed by equal channel angular pressing of eight passes, route Bc, at room temperature to produce the UFG material. Crystallographic texture and misorientation distributions were obtained locally from EBSD mappings at different radial positions after micro-extrusion. To model the strain path during micro-extrusion, the analytic flow line model of Altan etal. [J Mater. Process. Tech. 33 (1992) p.263] was used and also validated by finite element calculations. Modelling was carried out using the viscoplastic self-consistent (VPSC) model and a recently developed grain refinement model. The results showed large texture variations along the cross-section of the extruded sample for both UFG and CG copper. These cyclic drawing textures in UFG copper were simulated in good agreement with experiments using the presented modelling framework.

The influence of temporary hydrogenation on ECAP formability and low cycle fatigue life of CP titanium

It is generally believed that thermo-hydrogen processing has a beneficial effect on tensile ductility and fatigue properties of titanium. This study was concerned with investigating whether this also applies to titanium of commercial purity (CP) with an ultrafine-grained structure obtained by equal-channel angular pressing (ECAP). It was shown that despite the possibility to manipulate the microstructure of titanium the thermo-hydrogen processing offers, temporary hydrogenation was not able to improve ductility and low cycle fatigue life of CP titanium over the levels achievable by straight ECAP.

Bimodal grain size distributions in UFG materials produced by SPD - their evolution and effect on the fatigue and monotonic strength properties

In ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) techniques such as ECAP (equal channel angular pressing), bimodal grain size distributions have been observed under different circumstances, for example shortly after ECAP, after rest or anneal and/or after mild cyclic deformation at rather low homologous temperature. It has been shown that the mechanical monotonic and fatigue properties of some UFG materials can be modified (sometimes enhanced) by introducing a bimodal grain size distribution by a mild annealing treatment which leads, in some cases, to a good combination of strength and ductility. Here, the conditions under which bimodal grain size distributions evolve by (adiabatic) heating during ECAP and during subsequent annealing or cyclic deformation will be explored, and the effects on the mechanical properties, as studied by the authors and as reported so far in the literature, will be reviewed and discussed. In particular, the role of temperature rise during ECAP will be considered in some detail.

Comparison of different extrusion methods for compaction of powders

Densification of metallic powders by means of extrusion is regarded as a very attractive processing technique that allows obtaining a high level of relative density of the compact. However, the uniformity of the relative density depends on that of strain distribution and on the processing parameters. Several variants of extrusion can be used for compaction of metal particulates, including the conventional extrusion (CE) and equal channel angular pressing (ECAP), often referred to as equal-channel angular extrusion. Each of these processes has certain advantages and drawbacks with respect to compaction. A comparative study of these two extrusion processes influencing the relative density of compacts has been conducted by numerical simulation using commercial finite element software DEFORM2D. The results have been validated by experiments with titanium and magnesium powders and chips.

A comparison of continuous SPD processes for improving the mechanical properties of aluminum alloy 6111

Microstructure evolution, mechanical properties, formability, and texture development were determined for AA6111 samples processed by asymmetric rolling (ASR) with different roll friction, velocity, or diameters, conventional rolling (CR), and equal-channel-angular pressing (ECAP). Highly elongated or sheared grain structures were developed during ASR/CR and ECAP, respectively. ASR led to improved r-values and formability compared with CR primarily as a result of the development of moderate shear-texture components analogous to those developed during ECAP of billet material. ASR based on different roll diameters gave the best combination of strength, ductility, and formability.

Effect of ultrafine-grained titanium surfaces on adhesion of bacteria

The influence of the ultrafine crystallinity of commercial purity grade 2 (as-received) titanium and titanium modified by equal channel angular pressing (modified titanium) on bacterial attachment was studied. A topographic profile analysis of the surface of the modified titanium revealed a complex morphology of the surface. Its prominent micro- and nano-scale features were 100-200-nm-scale undulations with 10-15 microm spacing. The undulating surfaces were nano-smooth, with height variations not exceeding 5-10 nm. These surface topography characteristics were distinctly different from those of the as-received samples, where broad valleys (up to 40-60 microm) were detected, whose inner surfaces exhibited asperities approximately 100 nm in height spaced at 1-2 microm. It was found that each of the three bacteria strains used in this study as adsorbates, viz. Staphylococcus aureus CIP 68.5, Pseudomonas aeruginosa ATCC 9025 and Escherichia coli K12, responded differently to the two types of titanium surfaces. Extreme grain refinement by ECAP resulted in substantially increased numbers of cells attached to the surface compared to as-received titanium. This enhanced degree of attachment was accompanied with an increased level of extracellular polymeric substances (EPS) production by the bacteria.

An evaluation of an action research nursing documentation project

AIMS AND OBJECTIVES: The aim of this study is to describe healthcare professionals' experiences and perceptions of an intervention implemented in an action research project conducted to improve nursing documentation practices in four municipalities in Norway.

BACKGROUND: Documentation of individualized patient care is a continuing concern in healthcare services and could impacts the quality and safety of healthcare. Use of electronic systems has made some aspects of documentation more comprehensive, but creation of an individualized care plan remains a pressing issue.

DESIGN: A qualitative descriptive design was used.

METHODS: An action research project was conducted between 2010 and 2012 to improve the content and quality of nursing documentation in community healthcare services in four municipalities. One year after the project was completed four focus group interviews were conducted with healthcare professionals, one for each involved municipality. Two unit managers were interviewed individually. Qualitative content analysis was used.

RESULTS: Three themes emerged: healthcare professionals perceived competing interest; they experienced that they had to manage complexity and changes; and they highlighted a clear and visible leader as important for success.

CONCLUSIONS: Quality improvement activities are essential. Healthcare professionals experience a complicated situation when electronic health record systems do not support workflow. Further research is recommended to focus on the functionality and user interface of EHR systems, and on the role of leadership when implementing changes in clinical practice. This article is protected by copyright. All rights reserved.

Microstructure and electrical conductivity of aluminium/steel bimetallic rods processed by severe plastic deformation

Equal-channel angular pressing (ECAP) was used to fabricate Al/steel bimetallic rod for potential application in overhead transmission conductors. Bimetallic rods consisted of an austenitic stainless steel 316L core and an Al alloy 6201 cladding layer. By means of ECAP processing at 175°C, increase of mechanical strength without loss of electrical conductivity was achieved for one particular rod geometry out of three geometries tested. X-ray diffraction and transmission electron microscopy were employed to analyse how the microstructure was influenced by the number of processing passes and the bimetallic rod geometry. The co-deformation mechanism of the bimetallic rod under ECAP and accelerated dynamic ageing of Al alloy 6201 were discussed based on the microstructure characterisation results.

Bending fatigue testing of commercial purity titanium for dental implants

High fatigue strength is one of the major requirements for dental implant materials. It was previously shown that the fatigue strength under conventional stress-control tension–compression testing can be doubled for commercially pure (CP) titanium processed by equal channel angular pressing. However, the fatigue endurance of an implant exposed to cyclic loading in corrosive media (bodily fluids) may potentially be compromised. In this work, non-conventional bending fatigue testing in air and in simulated body fluid (SBF) has been carried out for coarse-grained and ultrafine-grained CP titanium.

Book review: Flight

‘Flight’ is the perfect metaphor for Frawley’s new-breed globalizing Irish emigrés and immigrés. Like everything about this novel, the epigraph, a dictionary definition, riffs on what flight might mean. The novel thoughtfully, deftly, interlaces a series of flights—to and from Ireland. Ireland has typically been a place of mass export of population, until the advent of the Celtic Tiger, or perhaps a decade or two before it began to rear up, and this novel set around 2004 but moving much further back in time, takes up issues of migration and refugees that became pressing in the prosperous years.

"To Hold the World in Contempt": The British Empire, War, and the Irish and Indian Nationalist Press, 1899-1914

The era between the close of the nineteenth century and the onset of the First World War witnessed a marked increase in radical agitation among Indian and Irish nationalists. The most outspoken political leaders of the day founded a series of widely circulated newspapers in India and Ireland, placing these editors in the enviable position of both reporting and creating the news. Nationalist journalists were in the vanguard of those pressing vocally for an independent India and Ireland, and together constituted an increasingly problematic contingent for the British Empire. The advanced-nationalist press in Ireland and the nationalist press in India took the lead in facilitating the exchange of provocative ideas—raising awareness of perceived imperial injustices, offering strategic advice, and cementing international solidarity. Irish and Indian press coverage of Britain’s imperial wars constituted one of the premier weapons in the nationalists’ arsenal, permitting them to build support for their ideology and forward their agenda in a manner both rapid and definitive. Directing their readers’ attention to conflicts overseas proved instructive in how the Empire dealt with those who resisted its policies, and also showcased how it conducted its affairs with its allies. As such, critical press coverage of the Boxer Rebellion, Boer War, Russo-Japanese War, and World War I bred disaffection for the Empire, while attempts by the Empire to suppress the critiques further alienated the public. This dissertation offers the first comparative analysis of the major nationalist press organs in India and Ireland, using the prism of war to illustrate the increasingly persuasive role of the press in promoting resistance to the Empire. It focuses on how the leading Indian and Irish editors not only fostered a nationalist agenda within their own countries, but also worked in concert to construct a global anti-imperialist platform. By highlighting the anti-imperial rhetoric of the nationalist press in India and Ireland and illuminating their strategies for attaining self-government, this study deepens understanding of the seeds of nationalism, making a contribution to comparative imperial scholarship, and demonstrating the power of the media to alter imperial dynamics and effect political change.

Factors Influencing Movements and Foraging Ecology of American Alligators (Alligator mississippiensis) in a Dynamic Subtropical Coastal Ecosystem

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.