Additively-manufactured Ti-6Al-4V (Ti64) exhibits high strength but in some cases inferior elongation to those of conventionally manufactured materials. Post-processing of additively manufactured Ti64 components is investigated to modify the mechanical properties for specific applications while still utilizing the benefits of the additive manufacturing process. The mechanical properties and fatigue resistance of Ti64 samples made by electron beam melting were tested in the as-built state. Several heat treatments (up to 1000 °C) were performed to study their effect on the microstructure and mechanical properties. Phase content during heating was tested with high reliability by neutron diffraction at Los Alamos National Laboratory. Two different hot isostatic pressings (HIP) cycles were tested, one at low temperature (780 °C), the other is at the standard temperature (920 °C). The results show that lowering the HIP holding temperature retains the fine microstructure (~1% β phase) and the 0.2% proof stress of the as-built samples (1038 MPa), but gives rise to higher elongation (~14%) and better fatigue life. The material subjected to a higher HIP temperature had a coarser microstructure, more residual β phase (~2% difference), displayed slightly lower Vickers hardness (~15 HV10N), 0.2% proof stress (~60 MPa) and ultimate stresses (~40 MPa) than the material HIP’ed at 780 °C, but had superior elongation (~6%) and fatigue resistance. Heat treatment at 1000 °C entirely altered the microstructure (~7% β phase), yield elongation of 13.7% but decrease the 0.2% proof-stress to 927 MPa. The results of the HIP at 780 °C imply it would be beneficial to lower the standard ASTM HIP temperature for Ti6Al4V additively manufactured by electron beam melting.

Organic nanostructures produced by a process of "bottomup" molecular recognition and self-assembly are key elements in nanotechnology applications. This use of synthetic building blocks with tailored reactivities is highly important for the production of advanced "smart" materials. While these building blocks possess many advantages in terms of synthesis, functionality, and chemical diversity, they usually have inferior mechanical properties compared to metallic nanostructures. Herein we report how indentation-type experiments conducted with an AFM using a diamond-tip cantilever demonstrated remarkable metallic-like point stiffness of up to 885 N m À1 and a Youngs modulus of up to 275 GPa for aromatic dipeptide nanospheres. This exceptional value makes these nanostructures the stiffest organic materials reported to date (they are even stiffer than macroscopic aramids), thus making them attractive building blocks for the design and assembly of ultrarigid materials with tailored molecular properties. The remarkable stiffness of these assemblies and their transparent optical properties make them ideal elements for the reinforcement of composite materials.The use of nanostructures for materials reinforcement is one of the most intriguing applications of nanotechnology.This includes far-fetched ideas such as the "space elevator" [1] to realistic objects including reinforced plastic for medical implants or dental materials. Biological material with nanoscale dimensions may have unique mechanical properties, as was demonstrated with spider silk that has a toughness 25 times larger per weight than that of steel. [2] While there has been much effort in the development of self-assembled protein and peptide nanomaterials, [3] these bioinspired assemblies are usually significantly less rigid than metallic structures.We probed the mechanical properties of nanospheres, which are formed by the self assembly of the Boc-Phe-Phe-OH peptide (Boc = tert-butoxycarbonyl, Phe = phenylalanine), a member of the aromatic dipeptide structural family that can form various nanoscale structures. [4] A phase diagram of the Boc-Phe-Phe-OH building block defines its assembly into a homogeneous population of either spherical or tubular nanostructures. [4c, 5] We used indentation-type experiments with AFM to study the mechanical properties of the spheres as this technique has a combination of low penetration depths and high lateral precision, which make it a powerful and attractive tool to measure the mechanical properties of nanoscale biological structures. [6] AFM has indeed been used to study the specific interactions of biomolecules at the single-molecule level by utilizing antibody-antigen interactions. [7] The Boc-Phe-Phe-OH peptide was dissolved in hexafluoro-2-propanol at a concentration of 100 mg mL À1 and then diluted with ethanol to form the spheres. The spheres were deposited on a mica surface and imaged using AFM (Figure 1 a) and SEM (Figure 1 b). We analyzed the size distribution of nearly 15 000 spheres from the SEM images. The sp...

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MgTiO3 is a material commonly used in the industry as capacitors and resistors. The high-temperature structure of MgTiO3 has been reported only for materials synthesized by the solid-state method. This study deals with MgTiO3 formed at low temperatures by the sol-gel synthesis technique. Co-precipitated xerogel precursors of nanocrystalline magnesium titanates, with Mg:Ti ratio near 1:1, were subjected to thermal treatment at 1200 °C for 5 h in air. A sample with fine powders of MgTiO3 (geikielite) as a major phase with Mg2TiO4 (qandilite) as a minor phase was obtained. The powder was scanned on a hot-stage X-ray powder diffractometer at temperatures between 25 and 890 °C. The lattice parameters and the atomic positions of the two phases were determined as a function of temperature. The thermal expansion coefficients of the geikielite were derived and compared with previously published data using the solid-state synthesis technique, providing insights on trends in materials properties at elevated temperature as a function of synthesis. It was found that the deviation of the present results in comparison to previously reported data do not originate from the method of synthesis but rather from the fact that there is an asymmetric solubility gap in geikielite. The lattice parameters of this study present the property of stoichiometric MgTiO3 and are compared to previously reported non-stoichiometric MgTiO3 with excess of Ti. The values of lattice parameters of the non-stoichiometric versus temperature of geikielite found the same for both solid-state reaction and sol-gel products.

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