Design of compositionally complex alloys with lamellar microstructures for laser cladding

In dieser Arbeit arbeiteten mehrere akademische Einrichtungen und Automobilzulieferer im Rahmen des europäischen Projekts $\textit {"Horizon 2020"}$ zusammen. Ziel war es Legierungen zu entwickeln, die zur Lebensdauerverlängerung von Warmumformwerkzeugen eingesetzt werden können. Dafür wurden die chemisch komplexen (CCA) Referenzwerkstoffe Al$_{0.6}$CoCrFeNi und Al${_0.75}$CoCrFeNi betrachtet, die eine grobe lamellare Mikrostruktur aufweisen. Zur Optimierung von Mikrostruktur und mechanischen Eigenschaften wurden verschiedene Legierungsstrategien angewandt, z.B. die Zugabe von Ti, Al und C, sowie die Substitution von Cr mit Mo. Nach eingehenden Untersuchungen wurde die Al$_{0.6}$CoCrFeNi CCA mit Ti- und C-Zusätzen ausgewählt und erfolgreich durch Laserauftragschweißen auf einen herkömmlichen H10-Werkzeugstahl aufgebracht. Aufgrund des Wärmeeintrags und der hohen Abkühlraten während des Laserauftragschweißens, zeigte die abgeschiedene CCA ein feines lamellares Gefüge mit hervorragenden mechanischen Eigenschaften.In this work, several academic institutions and automotive industry subcontractors worked together in a European project $\textit {"Horizon 2020"}$ to design new alloys that could be employed to extend the lifetime of hot forming tools used to produce B-pillars, which are key automotive parts for passenger safety. In this context, the reference materials Al$_{0.6}$CoCrFeNi and Al${_0.75}$CoCrFeNi compositionally complex alloys (CCAs), which exhibit coarse lamellar microstructures were considered. Several alloying strategies, including Ti, Al, and C additions as well as substitutions of Cr by Mo, were employed to optimize their microstructures and mechanical properties. An Al$_{0.6}$CoCrFeNi CCA with Ti and C additions was selected after thorough investigations and successfully processed by laser cladding on a conventional H10 tool steel. Owing to the thermal history and high cooling rates during laser cladding process the as-deposited CCA showed fine lamellar microstructures with superior mechanical properties

Adaptation of the Wound Healing Questionnaire universal-reporter outcome measure for use in global surgery trials (TALON-1 study): mixed-methods study and Rasch analysis

BackgroundThe Bluebelle Wound Healing Questionnaire (WHQ) is a universal-reporter outcome measure developed in the UK for remote detection of surgical-site infection after abdominal surgery. This study aimed to explore cross-cultural equivalence, acceptability, and content validity of the WHQ for use across low- and middle-income countries, and to make recommendations for its adaptation.MethodsThis was a mixed-methods study within a trial (SWAT) embedded in an international randomized trial, conducted according to best practice guidelines, and co-produced with community and patient partners (TALON-1). Structured interviews and focus groups were used to gather data regarding cross-cultural, cross-contextual equivalence of the individual items and scale, and conduct a translatability assessment. Translation was completed into five languages in accordance with Mapi recommendations. Next, data from a prospective cohort (SWAT) were interpreted using Rasch analysis to explore scaling and measurement properties of the WHQ. Finally, qualitative and quantitative data were triangulated using a modified, exploratory, instrumental design model.ResultsIn the qualitative phase, 10 structured interviews and six focus groups took place with a total of 47 investigators across six countries. Themes related to comprehension, response mapping, retrieval, and judgement were identified with rich cross-cultural insights. In the quantitative phase, an exploratory Rasch model was fitted to data from 537 patients (369 excluding extremes). Owing to the number of extreme (floor) values, the overall level of power was low. The single WHQ scale satisfied tests of unidimensionality, indicating validity of the ordinal total WHQ score. There was significant overall model misfit of five items (5, 9, 14, 15, 16) and local dependency in 11 item pairs. The person separation index was estimated as 0.48 suggesting weak discrimination between classes, whereas Cronbach's α was high at 0.86. Triangulation of qualitative data with the Rasch analysis supported recommendations for cross-cultural adaptation of the WHQ items 1 (redness), 3 (clear fluid), 7 (deep wound opening), 10 (pain), 11 (fever), 15 (antibiotics), 16 (debridement), 18 (drainage), and 19 (reoperation). Changes to three item response categories (1, not at all; 2, a little; 3, a lot) were adopted for symptom items 1 to 10, and two categories (0, no; 1, yes) for item 11 (fever).ConclusionThis study made recommendations for cross-cultural adaptation of the WHQ for use in global surgical research and practice, using co-produced mixed-methods data from three continents. Translations are now available for implementation into remote wound assessment pathways