High-throughput in-situ characterization and modelling of precipitation kinetics in compositionally graded alloys

The development of new engineering alloy chemistries is a time consuming and iterative process. A necessary step is characterization of the nano/microstructure to provide a link between the processing and properties of each alloy chemistry considered. One approach to accelerate the identification of optimal chemistries is to use samples containing a gradient in composition, ie. combinatorial samples, and to investigate many different chemistries at the same time. However, for engineering alloys, the final properties depend not only on chemistry but also on the path of microstructure development which necessitates characterization of microstructure evolution for each chemistry. In this contribution we demonstrate an approach that allows for the in-situ, nanoscale characterization of the precipitate structures in alloys, as a function of aging time, in combinatorial samples containing a composition gradient. The approach uses small angle x-ray scattering (SAXS) at a synchrotron beamline. The Cu-Co system is used for the proof-of-concept and the combinatorial samples prepared contain a gradient in Co from 0% to 2%. These samples are aged at temperatures between 450{\textdegree}C and 550{\textdegree}C and the precipitate structures (precipitate size, volume fraction and number density) all along the composition gradient are simultaneously monitored as a function of time. This large dataset is used to test the applicability and robustness of a conventional class model for precipitation that considers concurrent nucleation, growth and coarsening and the ability of the model to describe such a large dataset.Comment: Published in Acta Materiali

Incidence of lung tumours induced by urethane in mice exposed to reduced atmospheric pressure.

INBRED mice of strain A are well known to possess a high incidence of pulmonary adenomas whether spontaneous or induced, whereas strain C57B1 mice show a very low incidence, which according to Bloom and Falconer (1964) is genetically determined. In attempting to overcome this natural resistance of C57B1 mice to tumour development several observations led us to vary the oxygen tension in which mice were maintained. Heston and Pratt (1956, 1959) employed high or low oxygen tensions in a chamber for two days and found respectively increased or diminished incidences of dibenzanthracene-induced lung tumours in strain A mice. On the other hand, Mori-Chavez (1962b) observed an increase in the number and in the size of urethane-induced tumours in strain A mice maintained at a natural high altitude for eight or more months, and Heppleston and Simnett (1964) found that elevated oxygen tension produced deleterious effects on lung tissue and pulmonary adenomas from high incidence strains maintained in organ culture. Strains of mice susceptible and resistant to tumour induction by urethane were therefore exposed for prolonged periods to low atmospheric pressur