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Magnesium (Mg) and its alloys are promising materials for a wide range of biomedical applications due to its biodegradability. Nevertheless, their rapid corrosion dictates the need to develop strat...

As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well as favorable microstructures and, thus, mechanical properties. The present review paper therefore aims to present a critical analysis and overview of the relationship between processing parameters, microstructure, and mechanical properties of LMD components made from the Ti–6Al–4V alloy. Moreover, we discuss the applications of LMD parts in the aerospace and biomedical industries as well as the potential of LMD techniques for fabrication of more complex parts such as cellular structures. The paper concludes with a summary of the most important findings and suggestions for future research.

Although hydroxyapatite coatings have been proven effective for obtaining uniform and continuous coatings on metallic endosseous implants, the detachment of these coatings during implantation can critically compromise the hydroxyapatite bioactive role. In order to overcome this problem, this work proposes a new integrated approach, starting with the laser machining of the Ti6Al4V implant, followed by the allocation of the hydroxyapatite and its subsequent laser sintering. In this study two different powder compaction/laser sintering methods were tested. Hydroxyapatite sinterability and adhesion to the metal was assessed for both methods, considering several conditions. Hydroxyapatite possible degradation due to the temperatures achieved during this process was also evaluated by means of Energy Dispersive Spectrometry (EDS) and X-ray diffraction (XRD). The better solution assured a significant retained volume of non-degraded hydroxyapatite. This work proves that laser technology is a promising approach for the manufacturing of implants with improved bioactivity sites that can overcome the detachment problems of coating-based solutions.

Load-bearing implants success is strongly dependent on several physical and chemical properties that are known to drive cellular response. In this work, multi-material β-TCP-Ti6Al4V cellular structures were designed to combine Ti6Al4V mechanical properties and β-Tricalcium Phosphate bioactivity, in order to promote bone ingrowth as the bioactive material is being absorbed and replaced by newly formed bone. In this sense, the produced structures were characterized regarding roughness, wettability, β-TCP quantity and quality inside the structures after fabrication and the pH measured during cell culture (as consequence of β-TCP dissolution) and those aspects were correlated with cellular viability, distribution, morphology and proliferation. These structures displayed a hydrophilic behavior and results showed that the addition of β-TCP to these cellular structures led to an alkalization of the medium, aspect that significantly influences the cellular response. Higher impregnation ratios were found more adequate for lowering the media pH and toxicity, and thus enhance cell adhesion and proliferation., FCT (Fundação para a Ciência e Tecnologia) through the grants SFRH/BD/140191/2018; SFRH/BPD/112111/2015, SFRH/BD/128657/2017, SFRH/BD/141056/2018; SFRH/BPD/97701/2013, PD/BDE/127836/2016, and the projects PTDC/EMS-TEC/5422/2014_ADAPTPROSTHESIS and NORTE-01-0145-FEDER-000018-HAMaBICo. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941

This work was supported by FCT (Fundação para a Ciência e Tecnologia) through the grants SFRH/BPD/112111/2015, SFRH/BD/128657/2017, PD/BDE/127836/2016, SFRH/BPD/97701/2013, SFRH/ BD/141056/2018, SFRH/BD/140191/2018 and the projects PTDC/EMSTEC/5422/2014 and NORTE-01-0145-FEDER-000018-HAMaBICo. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941. Multi-material Ti6Al4V cellular structures impregnated with 45S5 bioactive glass were designed and produced using Selective LaserMelting (SLM), an additive manufacturing technique, combinedwith Press and Sintering focusing on load bearing components like hip implants. These structures were designed to combine Ti6Al4V mechanical properties and promote bone ingrowth into the structure as the bioactive material (45S5) is being absorbed and replaced by newly formed bone. The influence of these structures design on some of the physical and chemical aspects that drive cellular response was assessed. Roughness, wettability, bioactive glass quantity and quality on the structures after processing and the pH measured during cell culture (as a consequence of bioactive glass dissolution) were evaluated and correlated with cellular viability, cellular distribution, morphology and proliferation on the surface and inside the structures. info:eu-repo/semantics/publishedVersion

Osseointegration is defined by a stable and functional union between bone and a surface of a material. This phenomenon is influenced by the geometric and surface characteristics of the part where the bone cells will attach. A wide variety of studies proves that ceramic materials are strong competitors against conventional metals in the scope of bone tissue engineering. Ceramic scaffolds, porous structures that allow bone ingrowth, have been studied to enhance the osseointegration phenomenon. Geometric and dimensional parameters of the scaffold have influence in its performance as mechanical and structural supporter of bone growth. However, these parameters are conditioned by the manufacturing process by which these scaffolds are obtained. Several studies focusing on the production process of ceramic scaffolds have been developed, using 3D printing, stereolithography, selective laser sintering, green machining, robocasting, and others. The main purpose of this work is to evaluate and compare the different manufacturing processes by which ceramic scaffolds can be produced. This comparison addresses scaffold parameters like pore size, pore shape, porosity percentage, roughness, and so forth. Additionally, the different materials used in different manufacturing processes are also mentioned and discussed given its influence on a successful osseointegration while simultaneously displaying adequate mechanical properties. After making a screening on the available ceramic scaffolds manufacturing processes, several examples are presented, proving the potential of each of these manufacturing process for a given scaffold geometry.

The high temperatures generated in the cutting zone during machining processes results in an increase of wear mechanisms, reducing the lifetime of cutting tools. In this sense, cutting tools industry is constantly looking for new ways to reduce this temperature. This work proposes a novel cemented carbide cutting tool design and fabrication process for enhancing these tools thermal conductivity. This design incorporates copper heat sinks in designated strategic locations, fabricated using innovative laser green compacts machining. A thermal conductivity of 127 W/m.K was obtained for WC-Co/Cu, considerably higher than that of WC-Co (36 W/m.K). This approach for obtaining WC-Co/Cu cutting tools was found effective for increasing locally the thermal conductivity, especially in the cutting zone vicinity., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the project POCI-01-0145-FEDER-030353 (SMARTCUT) and also by the project NORTE 01-0145, FEDER-000018 (HAMaBICo). Additionally, this work is supported by FCT with the reference project UID/EEA/04436/2019. The authors would like to thank Miguel Ângelo Neto and Filipa Oliveira from University of Aveiro for helping in the 3D optical profilometry analysis.

The amount of hip revision surgeries is significantly increasing due to the loss of fixation between implant and bone, that leads to implant failure. The stiffness mismatch between Ti6Al4V hip implants and bone tissue, the non-uniform implant-bone contact pressure, and the poor wear resistance of Ti6Al4V are pointed as three critical issues that contribute to these implant's failure. In this study, a multi-material design and fabrication concept was exploited aiming to change traditional manufacturing paradigms, by allocating different biomaterials in a single component targeting a multi-functional hip implant. Selective Laser Melting technology was explored to fabricate NiTi-Ti6Al4V multi-material cellular structures with a Ti6Al4V inner region and a NiTi outer region. This work was focused on the SLM fabrication and processing parameters validation on a commercial SLM equipment. The morphological analyses allowed to assess a successful solidification and bond between NiTi and Ti6Al4V materials in the transition region. The shear tests revealed a high bond strength of the transition region with an average strength of 33 MPa. The nano-indentation results showed that the Ti6Al4V region exhibits a higher hardness and elastic modulus when compared with the NiTi region. This work is a part of a broader objective that aims to create a NiTi-Ti6Al4V multi-material and cellular structured hip implant capable to provide customized stiffness, superior wear resistance and a controlled NiTi outer region volume change., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/128657/2017 and the projects PTDC/EMS-TEC/5422/2014_ADAPTPROSTHESIS and UID/EEA/04436/2019.

Made available in DSpace on 2020-12-12T01:09:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Ti6Al4V cellular structures were produced by selective laser melting (SLM) and then filled either with beta-tricalcium phosphate (β-TCP) or PEEK (poly-ether-ether-ketone) through powder metallurgy techniques, to improve osteoconductivity and wear resistance. The corrosion behavior of these structures was explored considering its importance for the long-term performance of implants. Results revealed that the incorporation of open cellular pores induced higher electrochemical kinetics when being compared with dense structures. The impregnation of β-TCP and PEEK led to the creation of voids or gaps between the metallic matrix and the impregnated material which also influenced the corrosion behavior of the cellular structures. Center for Micro Electro Mechanical Systems (CMEMS) University of Minho (UMinho) MIT Portugal Program School of Engineering University of Minho Centre for Rapid and Sustainable Product Development Polytechnic Institute of Leiria Rua General Norton de Matos IBTN/Br – Brazilian Branch of the Institute of Biomaterials Tribocorrosion and Nanomedicine UNESP Campus de Bauru Av. Eng. Luiz Edmundo Carrijo Coube, 14-01 IBTN/Br – Brazilian Branch of the Institute of Biomaterials Tribocorrosion and Nanomedicine UNESP Campus de Bauru Av. Eng. Luiz Edmundo Carrijo Coube, 14-01

Nano and micro-sized metal particles are interesting solutions for several applications, from electronics to biomedical fields. In recent years, MgO has been gaining attention due to its nontoxicity and antibacterial activity, making this an interesting material for implants coating for instance. This study aims the fabrication/preparation of nanoparticles by laser ablation in liquid from the Mg bulk. The influence of liquid media and laser energy on the morphology, size and properties of the obtained nanoparticles was assessed. A Nd:YAG nanosecond laser of 1064 nm of wavelength at different laser energies was employed to irradiate Mg target in three environments (distilled water+SDS, ethanol and propanol). Ultraviolet–visible (UV–vis) absorption spectrophotometry, scanning electron microscopy with a transmission electron detector (STEM) and transmission electron microscopy (TEM) were used for characterizing the obtained particles, viz. particles’ mean size and size distribution. The composition of the obtained nanoparticles was analyzed by SAED patterns. The results showed that the characteristics of the obtained nanoparticles were prominently influenced by varying laser energy and liquid medium. The smaller particles are obtained when using ethanol and propanol (having 16.7 nm and 15.3 nm respectively), as compared to distilled water+surfactant.

Orthopaedic implants for load-bearing applications are usually composed of titanium-based materials. Aiming to propose a strategy able to improve the bone-implant interface on these implants, commercially pure titanium and Ti6Al4V alloy were subjected to anodic oxidation, hydrothermal treatment and to anodic oxidation followed by hydrothermal treatment and the produced oxide film was investigated. In addition, different mechanical (as-received vs mechanical polished) and chemical pre-treatments (alcohol cleaning vs acidic pre-treatment) were studied. No significant differences were found between the chemical pre-treatments, whereas upon different surface treatments the TiO2 layer presented different characteristics, namely regarding its crystallinity, roughness, thickness and wettability. The hydrothermal treatment followed by immersion for 24 h in 5XPBS was effective in creating a potentially bioactive oxide film, given the presence of anatase and rutile phases, and a hydrophilic layer for both Ti materials. Ti grade 2 subjected to alcohol cleaning and hydrothermal treatment resulted in a surface roughness of 226.7 ± 3.1 nm and water contact angle of 67.2 ± 8.7°, whereas for the Ti grade 5 subjected to the same surface treatment, Ra was equal to 20.4 ± 1.7 nm and the water contact angle to 83.5 ± 4.7°. In this context, the hydrothermal treatment is proposed as a simple treatment capable of improving the characteristics of the implant surface, thereby promoting osteoconductivity.

The development of high damping materials for noise reduction and attenuation of vibration on structural applications, such as automotive and aerospace industries, has been investigated. This experimental study is concerned with the damping capacity (tan delta) and dynamic Young's modulus (|E*|) of Silicon carbide (SiC) reinforced aluminium (Al) matrix composite. AlSi-SiCp composite was produced by hot pressing technique. Damping capacity and dynamic Young's modulus of composite and unreinforced AlSi alloy were studied using a dynamic mechanical analyser (DMA), over a temperature range of room temperature-400 °C (during heating and cooling phases), at 1 and 20 Hz. AlSi-SiCp composite showed higher damping capacity and dynamic Young's modulus than the AlSi unreinforced alloy. Furthermore, damping capacity was found to increase with temperature, while modulus decreases. The possible damping mechanisms are presented and discussed.

Aluminum-silicon (AlSi) composite reinforced with 20 wt% Ni particulates was produced by hot pressing and characterized using nanoindentation. Energy dispersive spectrometry and X-ray diffraction analyses showed that Al3Ni intermetallic was formed in the interface between Ni particulates and AlSi matrix. Chemical composition, hardness, and elastic modulus were studied along the interface from inner (near Ni) to outer (near AlSi) regions. A uniform composition was found throughout the interface, having 805.6 HV hardness and elastic modulus of 185.4 GPa. Interface properties have a crucial influence on the composite performance and their assessment is of paramount importance on composite properties estimation using predictive models.

In order to enhance osteointegration, prostheses surfaces are usually coated with bioactive materials like hydroxyapatite (HA), material found in teeth and bones. Traditional HA coatings were proven adequate for obtaining high-quality coatings on metal substrates. However, due to the implantation process, these coatings can be detached from the metal surface. In this work, a new materials design that aims to avoid this coating detachment scenario is proposed, based on composites of Ti6Al4V alloy reinforced with HA powder, with materials gradation from bulk to surface of the prosthesis, where the titanium bulk provides toughness and the outer regions provide biological performance. In order to assess the mechanical and biological performance of the prosthesis outer region, Ti6Al4V-HA composites with different HA contents were produced and characterized regarding microstructure and mechanical properties. Shear tests were performed and fracture surfaces were analysed. EDS and XRD analysis were performed in order to assess HA possible decomposition due to processing temperature and pressure during the hot pressing route. This work shows that the combination of hot pressing technique and an FGM design approach is a promising solution for manufacturing prosthesis with improved bioactivity that can overcome the detachment problems of solutions based on HA coatings. Keywords: Ti6Al4V, Hydroxyapatite, Hot pressing, Functionally graded material, Composite, Biomedical applications

The aim of this paper was to study the interface reaction between an AlSi alloy reinforced with Ni coated Multi-Wall Carbon Nanotubes (MWCNTs). A powder metallurgy processing route was used to produce AlSi composites. SEM, DSC, XRD and TEM analysis showed the formation of Al3Ni due to the presence of Al from AlSi matrix and Ni from CNT coating. This contributes to stress transfer from matrix to CNT reinforcement and consequently to enhancement of mechanical properties of the composites. Also it was observed some dissolution of Ni to AlSi and that the CNTs are very stable as they maintain their integrity. The coating of CNTs seems to be a good solution for application of this reinforcement in commercial alloys.

The effect of SiC particle size on the resultant damping capacity and dynamic modulus of aluminum metal matrix composites (AMMCs) was studied. Damping capacity, as well as dynamic Young's modulus, was measured at 1, 10 and 20 Hz, at room temperature. Image analysis and chemical composition were performed in order to investigate the AlSi–SiC interfacial reaction. The damping capacity of AlSi–SiCp composites, with three different particle size, was compared to AlSi unreinforced. The damping mechanisms involved were discussed in light of the results obtained from damping capacity. The results show that damping capacity and dynamic modulus of AlSi can be improved through the addition of SiC particles. Further, through a selection of specific sizes of SiC particles, it is possible to tailor the final composite stiffness and damping capacity.

This work is concerned with understanding the influence of reinforcement mechanisms of carbon nanotubes (CNTs) on mechanical, wear, and fatigue tests on an Aluminium-Silicon (AlSi) alloy. The reinforcement mechanism is presented through the observation of fracture morphology of the different tests. Results of mechanical properties, fatigue life performance, and wear loss is presented and discussed. It is shown that the CNTs reinforcement effect is active simultaneously in all previous properties and the reinforcement physical mechanism seems to be essentially due to a reinforcement effect of the interface that seems to be similar in all mentioned mechanical solicitations.

In this study, the effect of the size of SiC particle on high temperature damping capacity and dynamic Young's modulus of hot-pressed AlSi–SiC composites has been investigated. SiC particles with sizes of 13 μm, 38.8 μm and 118 μm were added to AlSi matrix to prepare the hot-pressed AlSi–SiC composites. These composites were characterized using a dynamic mechanical analyser (DMA), over a temperature range of room temperature to 400 °C. Regarding damping capacity, all AlSi–SiCp composites exhibited higher damping capacity compared to unreinforced AlSi alloy (for all tested frequencies). AlSi–SiCp(118) composites exhibited the highest improvement in damping capacity. A damping peak was observed near 250 °C, as a result of a relaxation process. Regarding dynamic Young's modulus, it was observed that the addition of SiCp to the AlSi alloy improved the Young's modulus. It was also demonstrated that by increasing the SiCp size, a decrease in Young's modulus is attained, with the highest improvement in dynamic Young's modulus being obtained by AlSi–SiCp(13) composite. Keywords: Metal matrix composites, Powder metallurgy, Hot pressing, SiC

The aim of this paper was to develop a method of producing Functionally Graded Materials (FGMs) by powder metallurgy whose principle is similar to the solid freeform fabrication. According to required FGM design, different chemical compositions can be obtained as the mixture of the powders continuously deposited in the matrix is computer controlled. Afterward the powders are pressed followed by sintering. The main advantage of the developed method is the control over the produced gradient and furthermore does not require burning binder phase. The resulting FGMs have a great interest from the possibility of controlling the composition or structure and thus obtaining components with desired properties. The technique introduced in this research is innovative because it can be achieved a continuous variation of composition along a given axis of a sample, as well as a greater diversification of the types of produced gradients. Keywords: FGMs, SiC, Steel, Processing

Orthopedic implants are under incessant advancement to improve their interactions with surrounding bone tissue aiming to ensure successful outcomes for patients. A successful biological interaction between implant and surrounding bone depends on the combination of mechanical, physical and topological properties. Hence, Ti6Al4V cellular structures appear as very promising solutions towards the improvement of conventional orthopedic implants. This work addresses a set of fundamental tools that allow improving the design of Ti6Al4V cellular structures produced by Selective Laser Melting (SLM). Three-point bending tests were carried out to estimate the elastic modulus of the produced structures. Morphological analysis allowed to evaluate the dimensional differences that were noticed between the model CAD and the SLM structures. Finite element models (adjusted CAD) were constructed with the experimentally obtained dimensions to replicate the mechanical response of the SLM structures. Linear correlations were systematically found for the dimensions of the SLM structures as a function of the designed model CAD dimensions. This has also been observed for the measured porosities as a function of the designed CAD models. This data can be used in further FE analyses as design guidelines to help engineers fabricating near-net-shape SLM Ti6Al4V cellular structures. Besides, polished and sandblasted surface treatments performed on the Ti6Al4V cellular structures allowed to obtain suitable properties regarding roughness and wettability when compared to as-produced surfaces. The capillarity tests showed that all the analyzed Ti6Al4V structures are able to transport fluid along its structure. The cell viability tests demonstrate Ti6Al4V cellular structures SLM produced did not release toxic substances to the medium, indicating that these structures can assure a suitable environment for cells to proliferate and attach. This study proposes a design methodology for Ti6Al4V cellular structures, that owe suitable mechanical properties but also provide a proper combination of porosity, roughness, wettability, capillarity and cell viability, all of them relevant for orthopedic applications. A Ti6Al4V cellular structured hip implant prototype gathering the suitable features addressed in this study was successfully SLM-produced., This work was supported by FCT through the grants SFRH/BD/128657/2017 and SFRH/BPD/112111/2015, the projects PTDC/EMSTEC/5422/2014 (ADAPTPROSTHESIS) and POCI-01-0145-FEDER030353 (SMARTCUT) and also by project NORTE 01–0145_FEDER000018. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2019, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145- FEDER-006941.

This work presents a novel texture design for implants surface functionalization, through the creation of line-shaped textures on Ti6Al4V surfaces and subsequent sintering of hydroxyapatite (HAp) powder into the designated locations. HAp-rich locations were designed to avoid HAp detachment during insertion, thus guaranteeing an effective osseointegration. This process starts by creating textured lines using a Nd:YAG laser, filling these lines with HAp powder and sintering HAp using a CO2laser. The adhesion of HAp is known to be influenced by HAp sintering parameters, especially laser power and scanning speed and also by the textured lines manufacturing. Different laser parameters combinations were used to assess the sintering and adhesion of HAp to the textured lines. HAp adhesion was assessed by performing high energy ultrasonic cavitation tests and sliding tests mimicking an implant insertion, with Ti6Al4V/HAp specimens sliding against animal bone. The HAp content retained after these tests was measured and results showed that an excellent HAp sintering and adhesion was achieved when using a scan speed of 1 mm/s and laser power between 9 and 9.6 W. It is important to emphasize that results indicated that the HAp bioactivity was maintained when using these conditions, validating this functionalization process for the production of hip prosthesis with improved bioactivity., FEDER -Federación Española de Enfermedades Raras(POCI-01–0145-FEDER-006941), info:eu-repo/semantics/publishedVersion

Carbon nanotube (CNT) incorporation in metal matrix composites is hampered by the development of attractive van der Waals forces, which lead to the formation of CNT agglomerates. Therefore, a detai...

Titanium and its alloys have been widely used in many engineering areas due to their properties. Despite having a high implant-tissue osseointegration time, Ti6Al4V has been extensively used in prosthesis and articular implants. To promote a faster bone ingrowth and consequently reduce the implant fixation time, the addition of a bioactive phase to form a biocomposite seems to be an excellent solution. Because of their bioactivity and similarity in composition with the human bone, HAp and b-TCP are two of the most widely used calcium phosphates in biomedical applications. To guarantee a strong adhesion of the previous bioactive materials in the implants surface, samples of Ti6Al4V, Ti6Al4V1HAp (10 vol %) and Ti6Al4V+beta-TCP (10 vol %) TCP were processed by the hot pressing technique. Tribological tests against Al2O3, lubricated in PBS at 37 ºC were carried out on a ball-on-flat reciprocating sliding geometry. Loads in the range of 3 N to 30 N were applied and their effect on the friction behavior and wear resistance of the tested materials was evaluated. Values of the coefficient of friction as well as the wear rate tend to increase with the addition of a bioactive phase to the Ti alloy. Micrographs of the worn surfaces showed that abrasion and plastic deformation are the prevailing wear mechanisms in the studied tribosystems. For biocomposites, particularly in the case of Ti6Al4V+HAp, pull-out of bioactive particle clusters has a determinant role on the tribological response, increasing both the friction coefficient and the specific wear rate., Contract grant sponsor: FCT (Fundac¸ao para a Ci ~ encia e Tecnologia—Portugal); contract grant numbers: NORTE-01-0145-FEDER-000018; UID/EEA/04436/2013, info:eu-repo/semantics/publishedVersion

The development of new design approaches for biomedical applications using conventional and well accepted bio inert materials is an actual challenge. This study proposes a bilayered materials design approach obtained by hot pressing and is concerned with the influence of sintering pressure on the interface reaction between titaniumalloy (Ti6Al4V) and zirconia (ZrO2), on density and mechanical properties of the Ti6Al4V-ZrO2. For this purpose, different sintering pressureswere studied (P=5, 20 and 100MPa). Bilayered materialswere produced by hot pressing process, at T=1175 °C. Microstructural characterization showed that Ti6Al4V reacts with ZrO2 (for Pâ ¥20 MPa) and that the interface reaction is strongly dependent on pressure. Additionally, an oxygen-deficient ZrO2 â x black zirconia layer was obtained for specimens produced at P=20 and 100MPa as result of decreased O/Zr ratio due to Ti diffusion into ZrO2 side. Young's modulus and hardness properties were evaluated by nanoindentation test. The results showed that these properties are influenced by sintering pressure, increasing with an increase on sintering pressure, with the highest improvement for specimens produced at higher pressure., This work is supported by FTC through the grant SFRH/BD/112280/ 2015 and the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145- FEDER-006941, and NORTE-01-0145-FEDER-000018-HAMaBICo., info:eu-repo/semantics/publishedVersion

The properties of parts produced by Selective Laser Melting (SLM) are highly influenced by the processing parameters. The calculation of the energy density is not enough for justifying the mechanical and physical properties, and understand the microstructures of Ti6Al4V samples produced by SLM. In fact, samples produced with the same energy density, but with different processing parameters, present distinct properties. In this sense, it is necessary to assess the influence of processing parameters on SLM fabrication, as isolated parameters but also their interactions.This work presents a study on the influence of several SLM processing parameters (laser power, scan speed and scan spacing) on density, hardness and shear strength of Ti6Al4V samples. The influence of these processing parameters on the final properties of SLM parts was obtained by using statistical analysis. Additionality, with the drive of finding the significant main factors and their interactions, analysis of variance (ANOVA) was performed. The influence of the above mentioned processing parameters on shear strength, hardness and density resulted in three models that can be used as predictive design tools for Ti6Al4V parts produced by SLM technology. Moreover, a study on the microstructures of the Ti6Al4V samples was performed and correlated with the obtained models. (C) 2016 Elsevier B.V. All rights reserved., This work is supported by FCT through the project with the reference EXCL/EMS-TEC/0460/2012 and the grant SFRH/BPD/112111/2015. This work is also supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 Programa Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941., info:eu-repo/semantics/publishedVersion

Au-50%Cu (at. %) alloy presents the shape memory effect (SME), which is dependent of the solid state transformation that happens during heating, after the introduction of an internal stress in the quenched state. The solid state phase transformation temperatures were determined by means of Differential Thermal Analysis (DTA), both in heating and cooling cycles. With the obtained DTA results, a sequence of high temperature X-ray diffraction (XRD) experiments were made, in order to confirm the presence of the solid state phase transformations and to determine their stable crystal structure and lattice parameters. These XRD results were compared with those obtained from the literature. The displacements of the lattice parameters were determined, for each equilibrium phase, for measurements at room temperature and at high temperature. The characteristics of the quenched samples were also studied in order to determine the phase transformations that are responsible for the shape memory effect in this alloy.

This study is concerned with the influence of sintering stage duration on the interface load transfer capacity between NiTi fibres and AlSi matrix alloy and thus in the final composite strength. Short-fibre-NiTi/AlSi composites were produced by a pressure-assisted sintering process, under vacuum, for sintering stages of 20, 25 and 60 min. All the obtained composites, with different sintering stages, have shown the occurrence of load transfer from the matrix to fibres, indicating the development of an effective interface between fibre and matrix. Performed shear tests have shown a decaying of shear strength with increasing sintering stage, in the selected range of sintering times, with the lowest sintering time leading to higher properties. It was also concluded that with increasing sintering stage, the interface volume around the fibres increases and the load transfer capacity decreases.

This paper is concerned in assessing the possibility of the use of a Directional Solidification (DS) process in order to produce functionally graded materials. It will be assessed the influence of the relative displacement rate between heating coil and mould, in order to evaluate the produced cooling rates along the casting and consequent metallurgical and mechanical properties on the obtained component. A copper-silver alloy, which is prompt to macro-segregation occurrence, will be used. Results demonstrate that the process, which is able to originate DS castings, may also be used for FGMs production.