Professional Language: Understanding and being understood

Language is a vital means of communication and education plays a key role in developing both our general language capabilities but also our use of "Professional language". Learning a professional language is like being inducted into the profession through the shared use of arcane and often obscure words and terminology. What makes sense to a “Professional" could well be gobbledygook/meaningless/nonsense to anyone else. This CPD activity is designed to encourage us to think about how we speak and communicate. In a multicultural country we have to be aware of both how we communicate and also how colleagues and patients are communicating

The effects of alloying additions in polycrystalline Co-Ni Superalloys

New Co-Ni superalloys are being considered as a potential replacement for current Ni superalloys used in gas turbine applications. Utilizing the stable L12 phase Co3(Al,W) discovered in 20061 M.Knop et al. developed the new γ/γ’ polycrystalline superalloy V208C, which exhibited favourable strength and oxidation performance when compared to existing Ni and Co superalloys2. Further work has now been done to evolve the alloy chemistry of V208C in order to make a step towards the next iteration of a potential candidate alloy. Using the nominal composition of V208C, 36Co-35Ni-15Cr-10Al-3W-1Ta-0.15C-0.2B-0.04Zr (at%), further additions of 1Cr, 1Al, 1Mo, 2Mo, 0.5Nb and a swap of the C/B content were investigated using a laboratory-scale cast and wrought process to produce a series of ingots for characterization. Differential scanning calorimetry (DSC) was used to determine the γ’ solvus temperatures of each alloy, with the 1Al addition providing the most significant increase from 1000°C to 1020°C. The oxidation performance of each alloy at 800°C for 100 hours was examined via a combination of thermogravimetric analysis (TGA) and focused ion beam (FIB) cross-sectioning of the oxide layers. The 1Al addition, again, exhibited the best oxidation performance, with the 1Mo addition also performing well. High-temperature tensile testing determined the yield strength of each specimen at room temperature and at 50°C intervals from 650-900°C. The alloys all displayed the flow stress anomaly; with 2Mo possessing the highest yield stress at room temperature and 1Al at the high-temperature peak. The γ’ fraction, size and distribution were observed using electron microscopy, indicating that the addition of 1Al caused the most significant rise in γ’ fraction from 50% to 53%. Special consideration was given to the C/B content swap in order to understand how it may effect the mechanisms of grain boundary precipitate formation, as well as the subsequent impact on strength performance. References: J. Sato, T. Omori, K. Oikawa, I Ohnuma, R. Kainuma and K. Ishida. Cobalt-base high-temperature alloys. Science, p90-91, 2007 M. Knop, P. Mulvey, F. Ismail, A. Radecka, K.M. Rahman, T.C. Lindley, B.A. Shollock, M.C. Hardy, M.P. Moody, T.L. Martin, P.A.J. Bagot and D. Dye. New Polycrystalline Co-Ni Superalloy. JOM, 201

Mechanisms of Elevated Temperature Galling in Hardfacings

The galling mechanism of Tristelle 5183, an Fe-based hardfacing alloy, was investigated at elevated temperature. The test was performed using a bespoke galling rig. Adhesive transfer and galling were found to occur, as a result of shear at the adhesion boundary and the activation of an internal shear plane within one of the tribosurfaces. During deformation, carbides were observed to have fractured, as a result of the shear train they were exposed to and their lack of ductility. In the case of niobium carbides, their fracture resulted in the formation of voids, which were found to coalesce and led to cracking and adhesive transfer. A tribologically affected zone (TAZ) was found to form, which contained nanocrystalline austenite, as a result of the shear exerted within 30{\mu}m of the adhesion boundaries. The galling of Tristelle 5183 initiated from the formation of an adhesive boundary, followed by sub-surface shear in only one tribosurface, Following further sub-surface shear, an internal shear plane is activated. internal shear and shear at the adhesion boundary continues until fracture occur, resulting in adhesive transfer.Comment: 9 pages, 12 Figure

Interface characteristics in an {\alpha}+{\beta} titanium alloy

The alpha/beta interface in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) is investigated via centre of symmetry analysis, both as-grown and after 10% cold work. Semi-coherent interface steps are observed at a spacing of 4.5 +/-1.13 atoms in the as-grown condition, in good agreement with theory prediction (4.37 atoms). Lattice accommodation is observed, with elongation along [-1 2 -1 0]alpha and contraction along [1 0 -1 0]alpha . Deformed alpha exhibited larger, less coherent steps with slip bands lying in {110}beta. This indicates dislocation pile-up at the grain boundary, a precursor to globularisation, offering insight into the effect of deformation processing on the interface, which is important for titanium alloy processing route design.Comment: Revised after revie

Shifting sediment dynamics in the Coos Bay Estuary in response to 150 years of modification

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(1), (2021): e2020JC016771, https://doi.org/10.1029/2020JC016771.Estuaries worldwide have experienced modifications including channel deepening and intertidal reclamation over several centuries, resulting in altered fine sediment routing. Estuaries respond differently based on preexisting geometries, freshwater and sediment supplies, and extents and types of modification. The Coos Bay Estuary in Oregon is a relatively small estuary with complex geometry that has been extensively modified since 1865. A sediment transport model calibrated to modern conditions is used to assess the corresponding changes in sediment dynamics. Over ∼150 years, channel deepening (from ∼6.7 to 11 m), a 12% increase in area, and a 21% increase in volume have led to greater tidal amplitudes, salinity intrusion, and estuarine exchange flow. These changes have reduced current magnitudes, reduced bed stresses, and increased stratification, especially during rainy periods. Historically, fluvially derived sediment was dispersed across broad, deltaic‐style flats and through small tidal channels. Now, river water and sediments are diverted into a dredged navigation channel where an estuarine turbidity maximum (ETM) forms, with modeled concentrations >50 mg/L and measured concentrations >100 mg/L during discharge events. This “new” ETM supplies sediment to proximal embayments in the middle estuary and the shallow flats. Overall, sediment trapping during winter (and high river discharges) has increased more than two‐fold, owing to increased accommodation space, altered pathways of supply, and altered bed stresses and tidal asymmetries. In contrast to funnel‐shaped estuaries with simpler geometries and river‐channel transitions, these results highlight the importance of channel routing together with dredging in enhancing sediment retention and shifting pathways of sediment delivery.The Science Collaborative is funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center (NAI4NOS4190145).2021-06-1

Slip intermittency and dwell fatigue in titanium alloys: a discrete dislocation plasticity analysis

Slip intermittency and stress oscillations in titanium alloy Ti-7Al-O that were observed using in-situ far-field high energy X-ray diffraction microscopy (ff-HEDM) are investigated using a discrete dislocation plasticity (DDP) model. The mechanistic foundation of slip intermittency and stress oscillations are shown to be dislocation escape from obstacles during stress holds, governed by a thermal activation constitutive law. The stress drop events due to -basal slip are larger in magnitude than those along -prism, which is a consequence of their differing rate sensitivities, previously found from micropillar testing. It is suggested that interstitial oxygen suppresses stress oscillations by inhibiting the thermal activation process. Understanding of these mechanisms is of benefit to the design and safety assessment of jet engine titanium alloys subjected to dwell fatigue

Alloying effects on the oxidation behaviour of shot-peened Co-Ni base Superalloys

The effect of shot-peening on the oxidation mechanism in Co-Ni alloys with different Co-Ni ratios and varying Cr and Al contents were investigated at 850 °C for 200 h. A characterization method using isotopic oxygen tracing combined with focused ion-beam secondary ion mass spectrometry (FIB-SIMS) was performed to study the oxidation mechanism in both conditions. Multi-layered oxides in both peened and un-peened conditions consisted of chromia-rich scale on the outermost surface and a protective alumina-rich layer as the internal scale. Internal oxidation to different depths occurred within the alloys with the formation of alumina particles within a γ\u27-depleted zone. The morphology of the sub-surface oxides differed between the two surface conditions examined. Oxidation performance was quantified by measuring cross-sectional damage depths of the outer scale (chromia) and the internal oxidation depth (oxide fingers and y’-depleted depth). Oxidizing environments can promote recrystallization in the near-surface of the shot-peened conditions. The sub-surface oxide penetration for the shot-peened condition occurs to a more uniform depth and is associated with the grain boundaries of small recrystallized grains. This work forms part of an ongoing investigation to determine the effects of shot-peening in this alloy system with the oxidation performance to equivalent polished material at 850 °C