Grain size effect on twin thickness has been rarely investigated, especially when the grain size is less than 1000 nm. In our previous work (Mater. Sci. Eng.A527, 3942, 2010), different severe plastic deformation techniques were used to achieve a wide range of grain sizes from about 3 μm to 70 nm in a Cu–30% Zn alloy. Transmission electron microscopy (TEM) revealed a gradual decrease in the deformation twin thickness with decreasing grain size. In the present work, high-resolution TEM was used to further identify deformation twins and measure their thickness, especially for grain sizes below 70 nm. The twin thickness was found to gradually reduce with decreasing grain size, until a critical size (20 nm), below which only stacking faults were observed. Interestingly, the relationship between twin thickness and grain size in the ultrafine/nanocrystalline regime is found similar to that in the coarse-grained regime, despite the differences in their twinning mechanisms. This work provides a large set of data for setting up a model to predict the twin thickness in ultrafine-grained and nanocrystalline face-centered cubic materials.

In this paper, we report on the microstructural evolution and mechanical properties of a 5052 Al alloy processed by rotationally accelerated shot peening (RASP). A thick deformation layer of ∼2 mm was formed after the RASP process. Nano-sized grains, equiaxed subgrains, and elongated subgrains were observed along the depth of the deformation layer. Dislocation accumulation and dynamic recrystallization were found primarily responsible for the grain refinement process. An obvious microhardness gradient was observed for all of the samples with different RASP processing parameters, and the microhardness in the top surface of 50 m/s-5 min RASP-processed sample is twice that of its coarse-grained (CG) counterpart. The yield strengths of the RASP-processed 5052 Al alloy samples were 1.4–2.6 times that of CG counterparts, while retaining a decent ductility (25–84% that of CG). The superior properties imparted by the gradient structure are expected to expand the application of the 5052 Al alloy as a structural material.

System architecture is important for the design of complex mechatronic systems because it acts as an intermediator between conceptual design and detail design. An explicit and exact system modeling language is imperative for successful architecture design. However, some deficiencies remain, such as the lack of geometry elements, hybrid behavior description, and specific association semantics for existing architecture modeling languages. In this study, a Systems Modeling Language extension for mechatronic system architecture modeling called ArchME is proposed. The requirements for the mechatronic System Modeling Language are analyzed, and the metamodels are defined. Then, the modeling elements are determined. Finally, the profiles based on the systems modeling language are defined to support the modeling of function, behavior, structure, and their association. This enables system designers to model the system architecture and facilitates communication between different stakeholders. A case study is provided to demonstrate the modeling capability of ArchME.

We conducted in-situ high-temperature neutron and X-ray diffraction studies on tetragonal PbTiO3. Using a combination of Rietveld analysis and Maximum Entropy Method, the nuclear and charge density distributions were determined as a function of temperature up to 460 °C. The ionic states obtained from charge density distributions reveal that the covalency of Pb–O2 bonds gradually weakens with increasing temperature. The spontaneous polarizations calculated from the contributions of ionic state, ionic displacement, and nuclear polarization, are in good agreement with the experimental measurements. This method provides an effective approach to determine spontaneous polarizations in multiferroics with high-current leakage and low resistance.

We have developed a novel method of reactive sintering under high pressure and high temperature conditions and have successfully synthesized bulk and nanostructured BC2N, BC4N, and diamond-SiC composites. The keys to this success are the careful preparation of precursor materials through high energy ball-milling and sensible tuning of the sintering conditions (pressure, temperature, and sintering time), leading to the formation of nano-scale features in the final synthesis products. The indentation measurements indicate that BC2N and BC4N have the Vickers hardness of 62 and 68 GPa, respectively, making them the second hardest materials known, second only to diamond. The high P-T reactive sintering results in a nanostructured diamond-SiC composite of high uniformity, low porosity, minimum residual silicon, and minimal quantities of graphite. It tunes subtle interplays of P-T-t to have fine control of thermodynamics and kinetics in the formation of diamond-SiC nanocomposites with nanocrystalline SiC matrix. The surface defects of micron/nano-diamonds are consumed by amorphous/molten silicon in the formation of nanocrystalline SiC matrix. It in turn greatly reduces the forming/mobility of microcracks thus leads to significant enhancement of fracture toughness (by as much as 50%) of the nano-composites without much compromising of hardness. The present study shows how to design/proceed a well controlled nano-synthesis so as to achieve great improvement in nano-mechanics for advance technological applications.

We have used synchrotron X-ray powder diffraction (SXRPD) to investigate the structural behavior of cesium dihydrogen phosphate upon heating. Temperature-resolved data collected at ambient-pressure demonstrate that a transition from the room-temperature monoclinic phase (P21/m; a=7.90Å, b=6.39Å, c=4.87Å, and β=107.64°) to a high-temperature cubic phase (Pm3m; a=4.96Å) occurs at T=237°C. The high-temperature phase is not stable under ambient-pressure conditions, even in the absence of further heating. On the other hand, SXRPD measurements carried out under high-pressure (∼1GPa) evidence a transition from monoclinic to a stable cubic phase (Pm3m, a=4.88Å) at a temperature within the 255°C-275°C range. A 1000-fold increase in the proton conductivity (indicating the transition to the superprotonic phase) was previously observed under the same non-ambient conditions. Therefore, our results represent strong evidence that the superprotonic behavior in cesium dihydrogen phosphate is associated with a monoclinic-to-cubic polymorphic structural transition and not with chemical modifications.

B6O crystal growth from the B–B2O3 system was investigated at 1700–2200 °C and 4.5–6.5 GPa by using two different sample assemblies. Single B6O crystals over 100 μm in size have been synthesized at 5.5 GPa and 2100 °C. This makes it possible to study the properties of this interesting material. The factors affecting the B6O crystal morphology, size, color, and growth process were discussed. The solubility of B6O in B2O3 flux was estimated at 5.5 GPa and different temperatures. On the basis of the experimental results, we suggest two methods to grow large B6O crystals.