This research shows the development of alternative Cu-based materials for applications where enhanced thermal properties are desired. Cu/AlN composites were fabricated from mixtures of pure Cu and copper plated AlN-Cu composite powders. The ceramic phase was added in amounts of 10, 20 and 30 vol.% and the mixtures sintered by pulsed electric current sintering process (PECS). The results showed that the AlN particles are homogeneously distributed in the copper matrix and that the true contacts between hard particles are reduced because of the deposited copper on their surfaces, improving the connectivity of the matrix phase and bonding at the metal-ceramic interface. The relative density of the Cu/AlN composites was major than 97% in all cases. Thermal conductivity of the composites was high and decreased with the ceramic content from 359 to 194 W/mK, for 10 and 30% AlN, respectively. The coefficient of thermal expansion followed a lineal behavior with temperature and is also reduced with the ceramic content.

In this study, the microstructural characterization of a superplastic Zn-Al-Ag alloy (72, 24, and 4 in % wt. respectively) by using spectroscopy analysis techniques was obtained. The X-Ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) techniques were used. The main objective of this alloy development is to improve its super-plasticity property and increases its corrosion resistance in acid rain environments. The effect of small grain microstructure of the alloy obtained at the end of the fabrication process improved the super-plasticity behavior. The result of the fabrication process was observed by the characterization of crystallographic phases (morphology, size and distribution) and the chemical composition. The obtained results by XRF shown that Zn was the higher proportion element, in addition the Ag (4% wt.) addition to Zn-Al base alloy improves the grain refinement, as was observed by the SEM characterization. The Ag3Al and AgZn3 intermetallic compounds homogeneously dispersed were observed in the microstructure of the Zn-Al solid solution phase. The size grain observed after the rolling process was less than 10 µm, and it was associated to one of the main characteristics of super-plasticity properties. The XRD analysis results corroborated the present phases in the alloy, as was identified with the SEM and EDS characterization.

The present investigation focused on evaluating the effects of different amounts of precipitates on tension and hardness properties of a Ti–6Al–4V alloy, for this, two sets of samples with bimodal and equiaxed microstructures were obtained by heat treatment process. After this, the samples were aged at 545 °C for holding times of 100 and 200 h. Observation of the aged samples in the scanning electron microscope revealed fine α2 (Ti3Al) particles precipitating in the α matrix of the alloy. Uni-axial tension tests and Vickers microhardness measurements were conducted on the unaged and aged samples. Experimental results show that ultimate strength and hardness of bimodal and equiaxed microstructures are significantly affected by the heat treatment applied to produce such microstructures. Also, it was found that the precipitation of α2 particles drastically reduced the plastic response of the Ti–6Al–4V alloy.

In this work, we study the hard-magnetic properties and its influence on the microstructure of MnBi-based glass-coated microwires obtained by Taylor-Ulitovsky process, as well as their magnetic and thermal dependence in the range of 200 K-360 K. We obtained glass-coated microwires pieces trough of the Taylor-Ulitovsky process. Glass-coated microwires exhibited the formation of Low-Temperature Intermetallic Phase (LTIP)-MnBi, as confirmed by scanning electron microscopy (SEM). Energy Dispersive Spectroscopy (EDS) elemental chemical composition analysis showed LTIP regions interspersed within Bi- and Mn-rich areas. Magnetic properties were determined by vibrating sample magnetometry (VSM), for which a considerable intrinsic coercivity field (iHc) up to 6000 Oe at 360 K, together with a saturation magnetization (Ms) of 57.49 emu/cm3. Therefore, this combination of properties renders LTIP is a promising precursor with potential for applications at high temperatures.

Fatigue behaviour of titanium reinforced with TiB particles fabricated by ‘plasma transferred arc solid freeform fabrication’ (PTA-SFFF) technique was investigated. Rotation bending fatigue tests were conducted following the MPIF 56 standard using the staircase method approach. Experimental data is used to calculate the fatigue strength and construct S-N curves, where the results were compared to a powder metallurgy FC0205 as a benchmark material. The titanium samples were found to exhibit superior fatigue behaviour in comparison to the reference FC0205 material, performing well above 1/3 of its ultimate tensile strength with a 90% survival fatigue strength of 244 +/- 98.3 MPa versus 141 +/- 17.4 MPa. Fatigue failure mechanisms of samples were identified by examination of the fracture surfaces through scanning electron microscopy (SEM) as well as using transmission-electron microscopy (TEM) and focused ion beam (FIB) analysis techniques. Fatigue crack propagation was either arrested or deflected when propagation occurred within the vicinity of the TiB intermetallics. Fracture surfaces of the titanium matrix displayed evidence of striations while the TiB intermetallic experience cleavage fracture.

This paper presents the results of a study on the impact of a precipitation hardening treatment on the mechanical properties of 17-4PH stainless steel open-cell foams produced using a powder-metallurgy-based process patented by the National Research Council Canada (NRC). Pre-alloyed powder was used to manufacture stainless steel (SS) foams with either medium or high porosity by changing the nature of the organic binder used to process the porous materials. Some of these were kept in the as-sintered state, while others were submitted to the H900 precipitation hardening treatment frequently prescribed for 17-4PH stainless steels.

Metallurgical and physical characterization was carried out on the resulting materials, along with mechanical testing at the micro (indentation testing) and macro (compressive testing) scales. It was found that the Medium-Porosity Foams (MPF) and High-Porosity Foams (HPF) had very different morphologies, the HPFs having a delicate porous structure featuring thin sintered walls with many openings (a.k.a. windows) between the main cells, while the MPFs exhibited much thicker walls with few windows connecting the larger pores. As expected from these foam morphologies, the mechanical properties of MPFs were much higher than those of the more porous and delicate HPF materials. For both foam types, the average mechanical properties were improved by the H900 treatment. A comparison with compressive properties of 17-4PH foams taken from the literature resulted in reasonable agreement. However, the large scatter observed on the average compressive properties of the NRC foams and the slightly different structure/composition of the literature materials mean that any comparison between these porous alloys must be interpreted with caution.

The aim of this research was to investigate the influence of substrate roughness on the adhesion and tribological performance of thin TiN coatings obtained by physical vapor deposition. For that purpose, substrates of AISI H13 steel with surface finishes of 0.06, 0.28 and 0.90 μm in Ra were coated with TiN under the same coating conditions. The chemical composition of the steel, as well as that of the TiN coating, were obtained using EDS analysis. Adhesion tests were carried out following the procedure of BSi 1071-8 standard while hardness was evaluated by ASTM C 1327-03. On the other hand, dry sliding friction tests were conducted with a pin-on-disk tribometer, according to the ASTM G 99-05 standard. This study showed that the roughness of the coating increases as the substrate roughness increases. Regarding adhesion and hardness, all the samples showed an adhesion class 1 according to the standard and a hardness value of 14.51 GPa. Nevertheless, the highest substrate roughness produced the best adhesion. On the other hand, the lowest values for the friction coefficient and wear behavior were obtained by the sample with the lowest substrate roughness of 0.06 µm. In addition, it was found that friction and wear increase when the substrate roughness increases.

In the industry, the titanium nitride (TiN) coating is widely used in cutting tools, decorative and corrosion protection film, but unfortunately, this coating presented a poor performance under some work condition. For that, different studies have been dedicated to improving its properties with the inclusion of a third element that modifies the film structure, chemical and mechanical properties. In this work, TiN layers with/without of Al, B, and Cr inclusion were studied in order to analyze their effect in the film tribological performance. These were deposited using cathodic arc PVD technic on AISI-M2 steel. They were chemical and structural characterized using EDX and XRD, respectively. While the film thickness was determinate using a ball-cratering technique. Their tribological performance was studied using a sliding reciprocating movement in dry conditions, under three loads, at 30 min against Al2O3 ball as counterbody. The resulting wear tracks were studied using optical microscopy in order to study the wear mechanism. Raman spectroscopy was used to determinate the chemical changes produced on wear zones and the lost material was measured with a stylus profilometer. As result, the structure and morphology were modified with the inclusion of the third element. The TiN with the inclusion of Al and B presented a higher friction force and wear rate than TiN films. While the TiN with Cr inclusion film presented the best tribological performance with lower wear rate and friction coefficient. The Raman studies did not showed considerable changes on the damage coted surface areas, except for TiAlN coating that show the M2 tool steel Raman spectra on the areas where the film was removed.

The purpose of this work is to study the effect of SiO2- and Al2O3-NPs on the microstructure and mechanical properties of the weld bead (WB) created by a process of Submerged Arc Welding (SAW) between two AISI 1025 steel plates. Also it was necessary consider the chemical compositions of slags and burned fluxes, in order to determine the elements that are deposited and contribute in the final microstructure of WB. The welding materials to form each WB were a M12K electrode, a commercial fused flux (CFF) and AISI 1025 steel plates bevelled at 45°. In addition SiO2- or Al2O3-NPs an ethylic alcohol mixture were applied directly to the beveled surfaces, just before the SAW process, which was carried out according to the AWS A5.17 norm. Microstructural and phase changes at the Heat Affected Zone (HAZ) and Welding Zone (WZ) were analysed by metallographic Optical and Scanning Electron Microscopies. The mechanical properties of the WBs were determined through Tensile, Charpy impact and Vickers Hardness tests. By means of metallography of WBs, it was determined that the length of the AF needles increases in 113 and 183 % when adding SiO2- or Al2O3-NPs, respectively. Related to the mechanical properties of the WB, the tensile and yield strength decreases with both additions, SiO2- or Al2O3-NPs. The microhardness at WZ was found to decrease by adding such oxide-NPs. Moreover, the impact energy absorbed by the WBs increases approximately by 83 or 57% due to SiO2- or Al2O3-NPs addition, respectively.

The viscoelastic properties of magnetorheological elastomers (MREs) are tunable with an external magnetic field, which provides them with greater functionality than conventional reinforced polymers. Despite the abundant amount of literature studying the complex micromechanics of MREs, the effect of filler morphology (including particle size, shape and superficial texture) is an aspect that has been recurrently overlooked. This paper presents a multiscale experimental investigation of the microscopic mechanisms governing the macroscopic viscoelastic behavior of PDMS-silicone-based MREs, with an emphasis on the effect of filler morphology on both the microstructure and the overall dynamic shear response of MREs. Sixteen different MREs were produced using four different iron powders of varying average particle size, shape and texture. The morphology of iron particles and the microstructure of the fabricated materials were analyzed via X-ray computed nanotomography and scanning electron microscopy. In addition, the shear moduli of the specimens were monitored under coupled magneto-mechanical loading via dynamic mechanical analysis. This study shows that the particle size affects the strength of the magnetic interparticle interactions, which produce a confining effect on the rubber matrix, while the particle shape and texture have a great influence on the rubber-filler mechanical adhesion.

A multi-scale analysis, ranging from μm → nm → Å-scaie on the influence of thermal treatment on the thermotropic copolyester based on 60 mol% (l,4)-hydroxybenzoic acid (B), 5 mol% (2,6)-hydroxynaphthoic acid (N), 17.5 mol% terephthalic acid (T) and 17.5 mol% biphenol (BP) - COTBP- was carried out. The Å and nm-scale structure was investigated by synchrotron scattering (WAXS and SAXS). Extruded tapes ca. 30 μm thick were annealed at 300 °C under air, without tension. WAXS revealed fibre-like structure with crystalline order, whereas SAXS patterns exhibited diamond-shaped diffuse scattering and discrete meridional scattering elucidating structures along the fibre axis and periodic crystallites. Heat treatment produced roughness reduction, and WAXS patterns showed reflections sharpening indicating an improvement of molecular register and packing (molecular alignment and degree of crystallinity Χ increased). Thermal treatment increased the thermal stability, melting transition and tensile Young’s modulus, E, along extrusion axis, whereas nanoindentation showed decrease of hardness and elastic modulus. Hence, a thermally-induced seif-reinforcing effect was evidenced, with microstructure reorganization correlating with improved thermo-mechanical properties.

PA6 and PMMA polymers with different MWCNTs addition (5, 7 and 9 wt %) were synthetized through casting solution, resulting in improvement properties in contrast to pristine polymers. SEM images showed the MWCNTs embedded into polymeric matrices. D, G and G´ bands of MWCNTs were confirmed by Raman spectroscopy and functional groups observed in both nanocomposites by FTIR demonstrated a strong interaction. A significant increasing in electrical conductivity and microhardness was observed in all the nanocomposites. Major microhardness values were obtained in MWCNTs/PA6 (50 HV) however the MWCNTs/PMMA nanocomposites showed the highest electrical conductivity value (6.4×10-4 S/cm).

By using electrochemical tests, small signal variations were study by digital signal processing techniques. Electrochemical noise and electrochemical polarization curves were very useful to obtained electrochemical behavior of alloys, but the low signal levels of measurements obtained showed that some of the information was not likely to be measured and, therefore, not being able to identify. Graphene oxides (GO) samples were prepared by ball milling procedure adding Lithium. SIGVIEW software was used for Digital Signal studies. Comparing, the signals obtained by electrochemical techniques and the research by computational tools; it was possible to find out a behavior path of samples. Display devices made by graphene were observed to provide new information about the structure of samples and how nanotechnology area can be improved. The current investigation aimed at maintaining electrochemical stability, since different deformations, as twisting and bending are quite relevant in portable electronics devices.

In the present study, aiming to control the setting reaction and to increase the strength of hydroxyapatite-based biocements, gelatin, citric acid and malonic acid, and combinations of them, were used as binders. The mechanical strength of the developed biocements was evaluated after 1 to 15 days of exposure (aging) to air with 100% relative humidity at 37-40 °C. Especially for the case of gelatin, the mechanical properties of the biocements increased as a function of aging time in the humid environment. In this case, the standard compressive strength increased from ∼19 to ∼40 MPa, while the diametral compressive strength increased from ∼2 to ∼12 MPa, between day 1 and day 15 of aging. These values are similar to those reported in the past for HAp-containing biocements added with a variety of organic or inorganic binders. However, the resulting setting times were too long. Thus, it was proposed that crosslinking of gelatin by a suitable chemical agent during the application of the prepared HAp-based biocements could be a potential way to control their handling and setting characteristics, while preserving their good mechanical properties, good biocompatibility, and good solubilization characteristics in the presence of biological fluids.