Embedded-atom method: Derivation and application to impurities, surfaces, and other defects in metals, Physical Review B 29, pp. 6443-6453. Daw, M., Foiles, S. M. and Baskes, M. (1993). The embedded-atom-method: A review of theory and applications, Material Science Report 9, pp. 251-310. Daw, M. S., Windl, W., Carlson, N. N. and Laudon, M. (2001). Effect of stress on dopant and defect diffusion in Si: A general treatment, Physical Review B 64, p. 045205. De Giorgi, E. (1975). Sulla convergenza di alcune successioni di integrali del tipo dell'areo,

No abstract

A number of preliminary observations have guided this The tensile creep behavior of two rare-earth dopant sysstudy. For example, it is known that the bulk solubility of Y 3ϩ tems, lanthanum-and yttrium-doped alumina, are comand La 3ϩ in alumina is very small 11,12 and the size mismatch pared and contrasted in order to better understand the role between Al 3ϩ and the aforementioned dopant cations is quite of oversized, isovalent cation dopants in determining creep large. Thus, it might be expected that Y and La ions will behavior. It was found that, despite some microstructural segregate preferentially to extended defects, such as free surdifferences, these systems displayed qualitatively a similar faces and grain boundaries. This expectation was validated in a improvement in creep resistance, supporting the hypothesis previous SIMS (secondary ion mass spectroscopy) mapping that creep is strongly influenced by segregation. Differences study 13 and STEM (scanning transmission electron microscopy) in primary creep behavior and activation energy for steadywork 14,15 in which both Y and La dopant segregation was state creep were, however, observed for these systems. Given observed. Indeed, sintering studies show that Y and La retard these results, it is expected that creep behavior can be furgrain growth and greatly reduce the densification rate in these ther optimized by adjusting the dopant level and by controlsystems. 16 Further, it has been reported that Y can reduce the ling the microstructure.growth of polycrystalline alumina scales. 17 As mentioned above, the present work consists of tensile I. Introduction creep testing and microstructural characterization of both Yand La-doped alumina. Microstructural analyses center on M ECHANICAL properties of structural ceramics in a highquantifying differences in average grain size and shape between temperature environment have been the subject of numerthese two systems as well as grain evolution during the test. The ous investigations over the years. For this reason, creep goal of this effort is to relate microstructural features of the properties have been studied and modeled extensively, and oxide to the (macroscopic) steady-state creep rate, as detercreep mechanisms are well-established. [1][2][3][4] In particular, much mined by a tensile creep test. As will be seen below, such comrecent work has involved the addition of impurities and the plementary testing is helpful in formulating structure-property tailoring of microstructures with the goal of obtaining desirable relations. properties over a range of temperatures. The creep rate in doped alumina depends strongly on the type of dopant, and most single dopants have been found either to increase the creep rate

▪ Abstract  Various methods for calculating the free energies of fluids, solids, and discrete spin systems are reviewed with particular emphasis on applications relevant in materials science. First, traditional methodologies based on harmonic approximations and thermodynamic integration are examined to highlight the workings of these very useful and robust techniques. Several newer and more specialized strategies are then discussed to provide a snapshot of current practices. Our aim here is to compare and contrast several related techniques and to provide an assessment of their relative strengths.

Grain boundaries can undergo phase-like transitions, called complexion transitions, in which their structure, composition, and properties change discontinuously as temperature, bulk composition, and other parameters are varied. Grain boundary complexion transitions can lead to rapid changes in the macroscopic properties of polycrystalline metals and ceramics and are responsible for a variety of materials phenomena as diverse as activated sintering and liquid-metal embrittlement. The property changes caused by grain boundary complexion transitions can be beneficial or detrimental. Grain boundary complexion engineering exploits beneficial complexion transitions to improve the processing, properties, and performance of materials. Here, we review the thermodynamic fundamentals of grain boundary complexion transitions, highlight the strongest experimental and computationalevidence for these transitions, clarify a number of important misconceptions, discuss the advantages of grain boundary complexion engineering, and summarize existing research challenges.

No abstract

No abstract

The field of multi-principal element or (single-phase) high-entropy (HE) alloys has recently seen exponential growth as these systems represent a paradigm shift in alloy development, in some cases exhibiting unexpected structures and superior mechanical properties. However, the identification of promising HE alloys presents a daunting challenge given the associated vastness of the chemistry/composition space. We describe here a supervised learning strategy for the efficient screening of HE alloys that combines two complementary tools, namely: (1) a multiple regression analysis and its generalization, a canonical-correlation analysis (CCA) and (2) a genetic algorithm (GA) with a CCA-inspired fitness function. These tools permit the identification of promising multi-principal element alloys. We implement this procedure using a database for which mechanical property information exists and highlight new alloys having high hardnesses. Our methodology is validated by comparing predicted hardnesses with alloys fabricated by arc-melting, identifying alloys having very high measured hardnesses.