Dry sliding wear behaviour of powder metallurgy Al-Mg-Si alloy-MoSi2 composites and the relationship with the microstructure

The effect of the microstructure on the dry sliding wear of six aluminium alloy 6061 matrix composites reinforced with 15vol.% of MoSi2 particles and two monolithic 6061 alloys processed by powder metallurgy with and without ball milling has been studied. Wear testing was undertaken using pin-on-ring configuration against an M2 steel counterface at 0.94m/s and normal load of 42, 91 and 140N. The wear resistance of the aluminium alloys was significantly improved by ball milling and the addition of reinforcing MoSi2 particles due to a more stable and more homogeneous microstructure, which avoids the detachment of the mechanically mixed layer. Wear rate of materials in T6 decreases as solutionized hardness of the materials increases. This behaviour is rationalized by taking into account the precipitation state of the matrix. In addition, wear rate follows a Hall-Petch type relationship, showing that the reduction of matrix grain size plays an important role in the increase in the wear resistance of the composites. The results indicate that the present intermetallic reinforced composites can be considered potential substitutes for ceramic reinforced aluminium alloys in tribological applications. © 2011 Elsevier B.V.Peer Reviewe

Psychosocial outcomes of an inclusive adapted sport and adventurous training course for military personnel.

PURPOSE: To explore the psychosocial outcomes of an inclusive adapted sport and adventurous training course that aims to support the rehabilitation and personal development of military personnel who have sustained physical and/or psychological disability. METHOD: Narrative life story interviews were conducted with 11 men aged 20-43 taking part in one of the 5-day courses. A thematic narrative analysis was conducted, focusing on accounts that provided insights into personally meaningful psychosocial outcomes of the course. FINDINGS: We identified six themes, falling into two distinct clusters. "Bringing me back to myself" was achieved through the themes of (1) returning to activity, (2) rediscovering a sense of purpose, and (3) reconnecting to others. "New rooms to explore" was realised through (4) experiencing new activities, (5) being valued/respected/cared for and (6) being inspired by other people. CONCLUSION: Involvement in the course stimulated a balance of present- and future-oriented psychosocial outcomes through which participants both recreated aspects of themselves that had been lost through injury/trauma and moved forward with their lives as a result of new horizons of possibility. IMPLICATIONS FOR REHABILITATION: This 5-day inclusive adapted sport and adventurous training course offered meaningful psychosocial outcomes among military personnel who had experienced physical and/or psychological disability. The course helped participants recover aspects of their previous life and self through becoming physically active again, rediscovering a sense of purpose and reconnecting to others. Participants describe a broadening of life horizons as a result of the course, through new activities, being valued/respected/cared for, and being inspired by other people

Coercivity and its thermal dependence in microsized magnetic particles: Influence of grain boundaries

Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1 powder particles have been obtained by gas atomization. Magnetization curves and coercivity were studied for particles ranging in size up to 1000μ. The overall magnetic behavior of such material is consequence of compositional heterogeneity of the microstructure as a whole. Anomalous temperature variation of coercivity (H_c) (i.e., a decrease in H_c with decreasing temperature) together with a decrease of saturation magnetization has been observed for less than 25 μm size. The origin of this behavior has been ascribed to metastable FeCu and FeNbSi phases in combination with an Fe-rich one. Making magnetic powders with coercive fields of the order of mOe remains a challenge for researchers. Our experiment has allowed us, at low temperature, achieving a coercive field of 9 Oe, much lower than those observed so far in this type of materials. This behaviour has been related with a FeCu phase present on grain boundaries

Anomalous low temperature stair like coercivity decrease due to magnetostatic coupling between superconducting and ferromagnetic particles in mixed powders

Magnetization curves of mixed Nb and FeSi based micrometric particles have been analyzed. The influence of the dispersion of Nb particles on the mixture remanence and coercivity has been studied above and below the Nb superconducting critical temperature. The hysteresis loop shows, at 5K and low applied fields, a decrease of both remanence and coercivity with respect to the one of pure ferromagnetic powders as well as a stair like profile. These features are explained as a consequence of the diamagnetic hysteresis loop of Nb giving rise to local stray fields acting on the ferromagnetic particles at its nearest neighboring

We haven't got a seat on the bus for you or All the seats are mine: Narratives and career transitions in professional golf

In this article we explore how the stories an athlete tells throughout life in sport affect her career transition experiences. We base our enquiry on a social constructionist conception of narrative theory which holds that storytelling is integral to the creation and maintenance of identity and sense of self. Life stories were gathered through interviews with two professional women golfers (Christiana and Kandy) over a six‐year period. Through a narrative analysis of structure and form we explored each participant’s stories of living in and withdrawing from professional golf. We suggest Christiana told monological performance‐oriented stories which, while aligning with the culture of elite sport, resulted in an exclusive athletic identity and foreclosure of alternative selves and roles. On withdrawal, Christiana experienced narrative wreckage, identity collapse, mental health difficulties and considerable psychological trauma. In contrast, Kandy told dialogical discovery‐oriented stories which, while being in tension with the dominant performance narrative, created and sustained a multidimensional identity and self. Her stories and identity remained intact, authentic and continuous on withdrawal from tournament golf and she experienced few psychological problems

Representability of Hilbert schemes and Hilbert stacks of points

We show that the Hilbert functor of points on an arbitrary separated algebraic stack is an algebraic space. We also show the algebraicity of the Hilbert stack of points on an algebraic stack and the algebraicity of the Weil restriction of an algebraic stack along a finite flat morphism. For the latter two results, no separation assumptions are necessary.Comment: 15 pages; major revision, final versio

Stories of success: Cultural narratives and personal stories of elite and professional athletes

Using a narrative methodology to explore the stories Olympic and elite athletes tell about success, we identified three alternatives to the dominant conception of success as the achievement of performance outcomes. In these alternatives, success is storied as: (1) ‘I did the best that I could’ – a controllable and sustainable story of effort and application; (2) ‘It’s the closest thing you can get to flying’ – a story where success relates to embodied experience and discovery; (3) ‘People I made the journey with’ – which prioritises relationships and connection between people. We reflect on three key insights: (1) success is a multidimensional concept, broader than the singular conception encapsulated within the dominant performance narrative; (2) through various narrative strategies, experienced athletes resist cultural pressures towards a singular conception of success; (3) for long-term performance and well-being, it is necessary to work towards multiple forms of success over time and across contexts

Narrative, identity, and recovery from serious mental illness: A life history of a runner

In recent years, researchers have investigated the psychological effects of exercise for people with mental health problems, often by focusing on how exercise may alleviate symptoms of mental illness. In this article I take a different tack to explore the ways in which exercise contributed a sense of meaning, purpose, and identity to the life of one individual named Ben, a runner diagnosed with schizophrenia. Drawing on life history data, I conducted an analysis of narrative to explore the narrative types that underlie Ben's stories of mental illness and exercise. For Ben, serious mental illness profoundly disrupted a pre-existing athletic identity removing agency, continuity, and coherence from his life story. By returning to exercise several years later, Ben reclaimed his athletic identity and reinstated some degree of narrative agency, continuity, and coherence. While the relationships between narrative, identity, and mental health are undoubtedly complex, Ben's story suggests that exercise can contribute to recovery by being a personally meaningful activity which reinforces identity and sense of self

Strengthening mechanisms in an Al-Fe-Cr-Ti nano-quasicrystalline alloy and composites

We report a study of the structure-processing-property relationships in a high strength AlFeCrTi nano-quasicrystalline alloy and composites containing 10 and 20 vol% ductilising pure Al fibres. The superimposed contributions of several different strengthening mechanisms have been modelled analytically using data obtained from systematic characterisation of the monolithic alloy bar. An observed yield strength of 544 MPa has been substantiated from a combination of solid solution strengthening, work hardening, precipitation hardening and Hall-Petch grain size dependent effects. These materials have been shown by other authors in previous published work to be highly sensitive to the size distribution of particles in the powder from which they are made, and the subsequent thermomechanical processing conditions. The processing condition employed in this study provided micron-sized grains with a strong [111] preferential orientation along the extrusion direction and a bimodal size distribution of the icosahedral nano-quasicrystalline precipitates. Both were deemed to be a significant contributor to the high yield strength observed. The addition of pure Al fibres was found to decrease the yield strength linearly with increasing Al content, and to augment the ductility of the composites.Industrial collaborator ALPOCO Ltd. (and more specifically Steve McArthur) provided the powders. Dr. Karen Kruska and Dr. Alan Xu assisted with sample preparation of FIB lift-out specimens of the atomised powder for TEM analysis. EPSRC Project EP/E040608/1 provided financial support. M. Galano thanks the RAEng for their support by means of a Research Fellowship. F. Audebert and M. Galano thank PICT-Oxford2010/2831. F. Audebert also thanks UBACyT20020130100663 and FONARSEC FS Nano 2010/11 for financial support.Peer Reviewe