Criteria for fast and selective α precipitation at β grain boundaries in Ti-alloys Consequence for in-service microstructures

International audienceThe potential for β grain boundaries (GBs) to give rise to large Widmanstätten colonies was determined through the observation of a large amount of precipitates at β GBs in a β-metastable titanium alloy using electron backscatter imaging and diffraction. The most critical boundaries are those which transform early and where a type of Variant Selection (VS) called double Burgers VS occurs. This mechanisms take place at 'special' β boundaries misoriented so that an α precipitate can be related to both grains through the Burgers relation. It was shown that the most critical GBs have a disorientation at an angle of less than 10° from 49.5°/<110> or 60°/<110>. A simulation study allowed those boundaries to be quantifed in crystallographic textures typical of industrial products. Those texture have then been discussed as a function of their potential to form large Widmanstätten colonies

Criteria for fast and selective α precipitation at β grain boundaries in Ti-alloys Consequence for in-service microstructures

International audienceThe potential for β grain boundaries (GBs) to give rise to large Widmanstätten colonies was determined through the observation of a large amount of precipitates at β GBs in a β-metastable titanium alloy using electron backscatter imaging and diffraction. The most critical boundaries are those which transform early and where a type of Variant Selection (VS) called double Burgers VS occurs. This mechanisms take place at 'special' β boundaries misoriented so that an α precipitate can be related to both grains through the Burgers relation. It was shown that the most critical GBs have a disorientation at an angle of less than 10° from 49.5°/ or 60°/. A simulation study allowed those boundaries to be quantifed in crystallographic textures typical of industrial products. Those texture have then been discussed as a function of their potential to form large Widmanstätten colonies

Transformation kinetics and microstructures of Ti17 titanium alloy during continuous cooling

International audienceWe have investigated the microstructure evolutions in the Ti17 near Click to view the MathML source titanium alloy during heat treatments. The phase transformation has first been studied experimentally by combining X-ray diffraction analysis, electrical resistivity and microscopy observations. From a series of isothermal treatments, a IT diagram has been determined, which takes into account the different morphologies. Then, a Johnson–Mehl–Avrami–Kolmogorov (JMAK) model has been successfully used to describe the phase transformation kinetics during either isothermal or cooling treatments. Finally, the coupling of the JMAK model to the finite element software ZeBuLoN allowed us to investigate the evolution of the spatial distribution of the different morphologies during the cooling of an aircraft engine shaft disk after forging

Późny przerzut do wątroby raka rdzeniastego tarczycy z niskim stężeniem kalcytoniny skutecznie wyleczony metodą radioablacji

  A 28-year-old female consulted in 1994 for a left thyroid nodule known for two years with documented progression. Left lobe resection was performed initially followed by total thyroidectomy without lymph node dissection in September 1994. Pathological examination concluded on unilateral 10 × 40 mm medullary thyroid carcinoma (MTC). RET mutation was negative. Basal and pentagastrin-stimulated CT levels had been normal from 1994 to 2008 when her CT level was found to be elevated at 33 ng/L and increased subsequently to 111 ng/L in 2010. In accordance with guidelines, cervical ultrasound was performed repeatedly with negative results. After discussion in a multidisciplinary meeting and with patient’s consent, an F-Dopa PET scan was proposed in disagreement with guidelines. This scan showed unique uptake in liver segment VI, which was confirmed by MRI. CT levels reached to 253 ng/L when she finally accepted treatment. In February 2013 we performed radiofrequency ablation of the lesion, which allowed normalisation of CT levels. This observation highlights the possibility of late recurrence of MTC. We could propose that for MTC patients with low-calcitonin levels-recurrences F-DOPA-PET/CT is a good diagnostic tool to use in case of repeatedly negative US neck studies. (Endokrynol Pol 2016; 67 (3): 326–329)    Chora w wieku 28 lat zgłosiła się do lekarza w 1994 roku z powodu lewostronnego guzka tarczycy wykrytego 2 lata wcześniej, z potwierdzoną progresją. Wykonano resekcję lewego płata tarczycy. Totalną tyreoidektomię wykonano we wrześniu 1994 roku bez usunięcia węzłów chłonnych. W badaniu patomorfologicznych stwierdzono jednostronnego raka rdzeniastego tarczycy (MTC) o wymiarach 10 × 40 mm. Wynik badania w kierunku mutacji RET był ujemny. Stężenia kalcytoniny (CT, calcitonin), podstawowe i po stymulacji pentagastryną, były prawidłowe od 1994 roku. Do 2008 roku, kiedy stwierdzono podwyższone stężenie CT wynoszące 33 ng/l, a następnie jego dalszy wzrost do 111 ng/l w 2010 roku. Zgodnie z zaleceniami powtórnie wykonano badanie USG szyi, w którym nie stwierdzono nieprawidłowości. Po omówieniu przypadku na spotkaniu wielodyscyplinarnego zespołu i uzyskaniu zgody chorej przeprowadzono badanie F-Dopa PET (niezgodnie z zaleceniami), w którym wykazano pojedyncze ognisko wychwytu w segmencie VI wątroby, co zostało potwierdzone w badaniu MRI. Kiedy chora w końcu zaakceptowała leczenie, stężenia CT zwiększyły się do 253 ng/l. W lutym 2013 roku wykonano ablację zmiany prądem o częstotliwości radiowej, co pozwoliło uzyskać normalizację stężeń CT w 2015 r. Ta obserwacja zwraca uwagę na możliwość późnej wznowy. Autorzy sugerują, że u chorych z MTC z ponownie stwierdzonym niskim stężeniem kalcytoniny wybór F-DOPA-PET/CT jako metody diagnostycznej jest dobrym rozwiązaniem w przypadku powtórnych ujemnych wyników USG szyi. (Endokrynol Pol 2016; 67 (3): 326–329)

Study of the precipitation of dispersoids during the homogenization treatment of a 3003 aluminium alloy

The phase transformation sequences have been studied for a commercial AA3003 alloy from the as-cast state during the heating to the homogenization temperature thanks to several in situ methods i.e. electrical resistivity, transmission electron microscopy and X-ray diffraction. The as-cast structure of this alloy is characterized by an inhomogeneous solid solution with primary Al6(Mn, Fe) and a few a-Al(Mn, Fe)Si particles. The in situ analysis are in good agreement which allow to clarify the phase transformation temperatures, the morphology of the precipitated phases and their crystallography.Les séquences de transformations de phase d'un alliage commercial AA 3003 ont été étudiées au chauffage depuis l'état brut de coulée jusqu'à la température d'homogénéisation à l'aide de plusieurs techniques in situ : résistivimétrie électrique, microscopie électronique à transmission et diffraction des rayons X. A l'état initial, l'alliage est constitué d'une solution solide sursaturée, de précipités Al6(Mn,Fe) et d'une faible quantité de précipités α-Al(Mn,Fe)Si. Ces différentes analyses ont donné des résultats en très bon accord et ont permis de préciser les températures de transformations de phase, la morphologie des phases précipitées ainsi que leur cristallographie

Effect of Processing Route on Microstructure and Mechanical Properties of a Ti-3Al-2.5V/TiB Composite

A Ti-3Al-2.5V matrix composite reinforced with 8.5 vol.% TiB was produced using a powder metallurgy route. Processing included the mechanical alloying of Ti-3Al-2.5V and TiB2 powders and Hot Isostatic Pressing (HIP) of the resultant composite powders, to produce a dense billet. These billets were subsequently extruded and/or subjected to various Conversion Heat Treatments (CHT), to complete the transformation of the TiB2 particles into TiB needles. The CHT was performed either before or after extrusion. Microstructures and tensile properties of the materials at each stage of the processing routes were investigated and compared to those of a non-reinforced Ti-3Al-2.5V material, manufactured by the same powder metallurgy route. It has been demonstrated that the processing routes have a great impact on the mechanical properties, through modifications of the matrix and reinforcement characteristics. Well-chosen processing routes lead to more ductile composites, though this gain in ductility leads to slightly lower stiffness and strength values. This study clearly demonstrates the possibility to produce, at an industrial scale, a ductile version of a highly reinforced titanium matrix composite, showing important application potential

Influence of the ageing conditions and the initial microstructure on the precipitation of α phase in Ti-17 alloy

The precipitation of α phase during ageing was investigated in the near-β titanium alloy Ti-17 considering either a fully βmetastable initial microstructure or a 35% αprimary + 65% βmetastable initial microstructure. In-situ electrical resistivity and high energy X-ray diffraction measurements revealed the influence of the initial microstructure, with different α morphologies (size and distribution of αprimary), as well as the heating rate on the precipitation sequences and kinetics following the decomposition of the β-metastable phase. Various amounts of metastable phases (ωisothermal and α″isothermal) precipitate in temperature ranges that increase with the heating rate. From temperatures about 500 °C, the orthorhombic α″isothermal structure evolved towards the hexagonal close-packed α as temperature increased. SEM microstructure characterisations showed that slow heating rates promoted a fine and dense α precipitate distribution through the formation of ωisothermal and/or α″isothermal, leading to higher hardness values. A higher heating rate restricted the precipitation of α″isothermal and shifted to the one of α at a higher temperature, leading to coarser precipitates. Furthermore, precipitation kinetics of α″isothermal/α were quicker considering an initial intragranular α precipitation as compared to α colonies

New facts on consumer price rigidity in the euro area

Usando microdatos del IPC para 11 países del área del euro, que representan el 60 % de la cesta europea de consumo durante el período 2010-2019, documentamos nuevos resultados sobre rigidez de precios en el área del euro: i) cada mes, en promedio, el 12,3 % de los precios sufren cambios, en comparación con un 19,3 % en Estados Unidos; cuando excluimos cambios debidos a descuentos, sin embargo, la proporción de precios que se ajustan cada mes cae al 8,5 % en el área del euro, y es del 10 % en Estados Unidos; ii) existen pocas diferencias en rigideces de precios entre los distintos países, y estas son mayores entre sectores; iii) la mediana de la distribución de incrementos (descensos) de precio es del 9,6 % (13 %) incluyendo descuentos y del 6,7 % (8,7 %) excluyéndolos; la heterogeneidad entre países es más pronunciada en el tamaño del cambio de precios que en la frecuencia del cambio; iv) la distribución de cambios de precio tiene una alta dispersión: el 14 % de los cambios de precio en valor absoluto son menores del 2 % y el 10 % exceden el 20 %; v) la frecuencia de cambios de precio apenas cambia con la inflación y responde muy poco a perturbaciones agregadas, y vi) cambios en la inflación vienen mayormente determinados por movimientos en el tamaño del cambio de precios; si descomponemos este efecto, los cambios en la proporción de incrementos de precio tienen mayor peso que los cambios en el tamaño de estos y que en el tamaño de las disminuciones de precio. Estos resultados son coherentes con las predicciones de un modelo de costes de menú en un contexto de baja inflación en el que las perturbaciones idiosincrásicas son más relevantes que las perturbaciones agregadas para explicar los ajustes de precios.Using CPI micro data for 11 euro area countries, covering 60% of the European consumption basket over the period 2010-2019, we document new findings on consumer price rigidity in the euro area: (i) on average 12.3% of prices change each month, compared with 19.3% in the United States; however, when price changes due to sales are excluded, the proportion of prices adjusted each month is 8.5% in the euro area versus 10% in the United States; (ii) the differences in price rigidity are rather limited across euro area countries and are larger across sectors; (iii) the median price increase (decrease) is 9.6% (13%) when including sales and 6.7% (8.7%) when excluding sales; cross-country heterogeneity is more pronounced for the size of the price change than for the frequency; (iv) the distribution of price changes is highly dispersed: 14% of price changes are below 2% in absolute values, whereas 10% are above 20%; (v) the frequency of price changes barely changes with inflation and it responds very little to aggregate shocks; (vi) changes in inflation are mostly driven by movements in the overall size of the price change; when this effect is broken down, variations in the share of price increases have a greater weight than changes in the size of the price increase or in the size of the price decrease. These findings are consistent with the predictions of a menu cost model in a low-inflation environment in which idiosyncratic shocks are a more relevant driver of price adjustments than aggregate shocks

Carbon content evolution in austenite during austenitization studied by in situ synchrotron X-ray diffraction of a hypoeutectoid steel

Using in situ high energy X-ray diffraction study of austenite formation in hypoeutectoid steel with three differ- ent initial microstructures (ferrite-pearlite, tempered martensite and bainite), the lattice parameters of ferrite, cementite and austenite are examined on heating at 0.25, 10 and 100 °C/s. The lattice parameters of ferrite, cementite and austenite do not vary linearly with the temperature, especially, in the temperature range where the austenitization takes place. For the austenite, it is suggested that the deviation from the linearity is mainly associated to the carbon content variation. Using Dyson and Holmes equation, the carbon content in austenite is evaluated for any moment of the austenite formation for each initial microstructure and all heating rates. For the ferrite-pearlite microstructure heated at 0.25 °C/s, the carbon content in austenite after complete cementite dissolution corresponds to that of pearlite. Moreover, a rapid decrease in carbon content in the austenite is observed during the first stage of the austenitization (simultaneous dissolution of ferrite and cementite) followed by a slow further decrease during the transformation of the remaining ferrite. The obtained results are discussed using thermodynamic calculations