To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Developing metallic materials with a good combination of strength and ductility has been an unending pursuit of materials scientists. The emergence of high/medium-entropy alloys (HEA/MEA) provided a novel strategy to achieve this. Here, we further strengthened a strong-and-ductile MEA using a traditional solid solution strengthening theory. The selection of solute elements was assisted by mechanical property and microstructure predictive models. Extensive microstructural characterizations and mechanical tests were performed to verify the models and to understand the mechanical behavior and deformation mechanisms of the designated CoCrNi–3W alloy. Our results show good experiment-model agreement. The incorporation of 3 at.% W into the ternary CoCrNi matrix increased its intrinsic strength by ∼20%. External strengthening through microstructural refinement led to a yield strength nearly double that of the parent alloy, CoCrNi. The increase in strength is obtained with still good ductility when tested down to 77 K. Nanoscale twin boundaries are observed in the post-fracture microstructure under 77 K. The combination of strength and ductility after W additions deviate from the traditional strength-ductility-trade-off contour.
Alnico alloys have long been used as strong permanent magnets because of their ferromagnetism and high coercivity. Understanding their structural details allows for better prediction of the resulting magnetic properties. However, quantitative three-dimensional characterization of the phase separation in these alloys is still challenged by the spatial quantification of nanoscale phases. Herein, we apply a dual tomography approach, where correlative scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectroscopic (EDS) tomography and atom probe tomography (APT) are used to investigate the initial phase separation process of an alnico 8 alloy upon non-magnetic annealing. STEM-EDS tomography provides information on the morphology and volume fractions of Fe–Co-rich and Νi–Al-rich phases after spinodal decomposition in addition to quantitative information of the composition of a nanoscale volume. Subsequent analysis of a portion of the same specimen by APT offers quantitative chemical information of each phase at the sub-nanometer scale. Furthermore, APT reveals small, 2–4 nm Fe-rich α1 phases that are nucleated in the Ni-rich α2 matrix. From this information, we show that phase separation of the alnico 8 alloy consists of both spinodal decomposition and nucleation and growth processes. The complementary benefits and challenges associated with correlative STEM-EDS and APT are discussed.
We have developed a fiber-based confocal optical microscope that operates inside of a commercial scanning electron microscope (SEM) instrument (JEOL 6400; JEOL Ltd., Tokyo, Japan) enabling the excitation of a sample either by a laser or by electron beam, and hence combining the complimentary techniques of photoluminescence and cathodoluminescence. The instrument uses single-mode fibers that enter the SEM by vacuum feedthroughs. The illumination and collection fibers operate as effective pinholes providing, in combination with a microscope objective (NA = 0.3), high spatial resolution (~2 μm) and excellent collection efficiency. The high spatial resolution ensures that the light collected from the sample is in a region of optimal laser beam and electron beam overlap. The capabilities of this instrument are tested by experiments involving the excitation of europium ions in situ doped in GaN thin films.
In-situ doped Eu ions in GaN grown by Organometallic Vapor-phase Epitaxy (OMVPE) at different pressures were investigated under different excitation methods and through the use of the following experimental techniques: (1) resonant site-selective laser irradiation (2) electron beam excitation, and (3) a dual excitation using a combination of electron beam and laser irradiation. With these means, we have examined the difference in the excitation pathways that result from resonant laser and electron hole (e-h) pair excitation of Eu ions for two different distinct incorporation sites, which are responsible for most of the luminescence. We have obtained clear evidence that e-h pairs do not have the ability to excite all of the ions and that there is excitation trapping by defects involved in the Eu excitation.
Email your librarian or administrator to recommend adding this to your organisation's collection.