CIP-FAST: assessing the production of complex geometry titanium components from powders by combining Cold Isostatic Pressing (CIP) and Field Assisted Sintering Technology (FAST)

A novel, two-step, solid-state method to produce complex geometry titanium parts was investigated by combining Cold Isostatic Pressing (CIP) with Field Assisted Sintering Technology (FAST). Hydride-dehydride powders of commercially pure titanium and Ti-6Al-4V were CIP’ed into shaped compacts using silicone moulds, then further consolidated using FAST, with ZrO2 powder as a secondary pressing media. The final parts retained the complex features from the CIP moulds but were compressed in the pressing axis. Densities >99% were achieved, with optimised FAST processing parameters required for the different alloys. High hardness and fine equiaxed microstructures were observed at the edges of the parts, suggesting oxygen transfer from the ZrO2 pressing media had occurred, with more investigation needed to better understand and prevent this. Despite this, the CIP-FAST process route has been demonstrated to be a fast, low-cost and material-efficient option to produce a wide variety of complex titanium parts

Powder production, FAST processing and properties of a Nb-silicide based alloy for high temperature aerospace applications

A Nb-silicide based alloy with nominal composition Nb–18Ti–22Si–6Mo-1.5Cr–2Sn-1Hf (at. %), designed for high temperature aerospace applications, was produced via a powder metallurgy (PM) route. The raw elements were arc melted, crushed, and milled to powder, then consolidated using Field Assisted Sintering Technology (FAST). The compressive creep of the alloy was evaluated using electro-thermal mechanical testing (ETMT). The study demonstrated the production of larger 60 mm diameter samples, with potential for further scale up. The microstructure of the FAST alloy, which is comprised of bcc Nbss and tetragonal αNb5Si3 was more homogenous compared with the cast alloy, with some interstitial contamination that occurred during powder production. The FAST alloy had lower density than state of the art Ni-based superalloys and refractory metal complex concentrated alloys (RCCAs) and high entropy alloys (RHEAs), and its yield strength and specific yield strength was higher than those of the latter metallic Ultra high temperature materials (UHTMs) and comparable to those of Nb-silicide based alloys with B addition. The stress exponent n in compressive creep was in the range 1.7–2.6, similar to that of binary Nb–10Si and Nb–16Si alloys and its creep rate at 1200 °C and 100 MPa was similar to that of the MASC alloy (Nb–25Ti–16Si-8Hf-2Al–2Cr (at.%)). Like the latter, the creep of the FAST alloy did not meet the creep goal

Composition and phase structure dependence of magnetic properties for Co2FeCr0.5Alx (x=0.9, 1.2) multi principal component alloys

This article investigates the microstructure evolution, phase formation, and magnetic properties of Co2FeCr0.5Alx (x = 0.9, 1.2) complex component alloys, as a function of heat treatment temperatures (at 500, 600, 700, and 1150°C), using XRD, optical microscopy, electron microscopy and vibrating sample magnetometry (VSM). The alloy with 20.4 at% Al (x= 0.9), identified here as C1, consisted of microscale BCC1 phase and BCC nanoscale particles containing mainly Fe and Cr, and B2 matrix with mainly Al and Co. Partial transformation of the BCC1 phase to an FCC phase was observed at 700°C and full transformation at 1150°C, through twinning. For the sample with 25.5 at% Al (x= 1.2), identified as sample C2, there were only nanoscale BCC particles in the B2 matrix with the same element segregation between the phases as C1. This increase in Al (from x= 0.9 to 1.2) content stabilised the B2 matrix phase, reduced the grain size, and increased both saturation magnetisation (Ms) and coercivity (Hc). Moreover, increasing the heat treatment temperature resulted in an increase in grain size of the B2 matrix, volume fraction and average size of the micro BCC 1 and nanoscale BCC phases for both C1 and C2, which also modified the soft magnetic properties, with Ms and Hc increasing up to 600°C followed by a decrease until 1150°C. Using the structural information as inputs for density functional theory calculations of Hc and Ms, it has been found that the Hc is influenced by the grain size of the matrix, and the volume fraction and size of the BCC1 phase at temperature higher than 600°C for C1 and 700°C for C2, but is controlled by nanoscale BCC particles below these temperatures. The Ms is controlled by the elemental diffusion and segregation. Thus, the best combination of Hc and Ms was seen with antiferromagnetic Cr segregated and partitioning in the microscale BCC1 phase, and a B2 matrix with less Cr rich precipitation, formed at 500°C, where the misfit strain between B2 matrix and nanoscale BCC was low

Genome-wide association study identifies variants in the MHC class I, IL10, and IL23R-IL12RB2 regions associated with Behcet's disease

Behcet's disease is a genetically complex disease of unknown etiology characterized by recurrent inflammatory attacks affecting the orogenital mucosa, eyes and skin. We performed a genome-wide association study with 311,459 SNPs in 1,215 individuals with Behcet's disease (cases) and 1,278 healthy controls from Turkey. We confirmed the known association of Behcet's disease with HLA-B*51 and identified a second, independent association within the MHC Class I region. We also identified an association at IL10 (rs1518111, P = 1.88 x 10(-8)). Using a meta-analysis with an additional five cohorts from Turkey, the Middle East, Europe and Asia, comprising a total of 2,430 cases and 2,660 controls, we identified associations at IL10 (rs1518111, P = 3.54 x 10(-18), odds ratio = 1.45, 95% CI 1.34-1.58) and the IL23R-IL12RB2 locus (rs924080, P = 6.69 x 10(-9), OR = 1.28, 95% CI 1.18-1.39). The disease-associated IL10 variant (the rs1518111 A allele) was associated with diminished mRNA expression and low protein production

A Comparative Study on Boride Layer Morphology of Fe-4Co, Fe-4V and Fe-4W Binary Alloys

In this study, the pack boronizing behavior of Fe-4M alloys (at.% M=W, V, Co) along with pure iron was investigated. The boronizing process was carried out at 1100°C for 3 h. The morphology, microstructure, boride layer thickness and surface properties of the formed boride layers were characterized by XRD, SEM-EDS and profilometry. The average boride layer thicknesses were 85 μm, 130 μm, 275 μm and 280 μm for Fe-4W, Fe-4V, Fe-4Co binary alloys and pure Fe, respectively. The surface roughness was not changed with the addition of alloying element into the substrate. FeB and Fe₂B phases exist on all boronized samples, but their ratio changes owing to alloying elements in the substrate. The saw-tooth morphology has transformed to a smoother boride layer with the addition of alloying elements of W and V, though Co addition was ineffective on saw tooth morphology. In addition, a transition zone under the boride layer was observed for the boronized Fe-W and Fe-V alloys. The formation of precipitates of boride of alloying elements was evident in the boride layer and in the transition zone for borided Fe-4V and Fe-4W alloys. Co has made a solid solution with iron in boride by replacing iron in the boride lattice

The Effect of Surface Polishing on the Flexural Strength of Anorthite-based Porcelainised Stoneware

The effect of surface polishing on the flexural strength of anorthite based porcelainised stoneware was studied. The flexural strength results obtained from both polished and unpolished samples were analysed by using Weibull statistical method. The state of surfaces and microstructures of polished and unpolished samples were also characterised by profilometry and scanning electron microscopy. Typical flexural strength value obtained from anorthite based stoneware body fired at 1210°C was about 100 MPa. The average flexural strength (σ_{m}) and Weibull modulus (m) values for as fired, ground, and ground and polished specimens increased sequentially with polishing degree. The surface roughness measurements and microstructure observations showed that the severity of the surface flaws declined as the polishing process proceeded. The obtainment of better strength behaviour with polishing was attributed to high crystalline to glassy phase ratio of the anorthite based porcelainised stoneware together with the formation of network structure of these anorthite crystals

Oxide Based Ceramic Coating on Al-4Cu Alloy by Microarc Oxidation

In this study the Al-Cu aluminum alloy with 4 wt% Cu was prepared under controlled atmosphere and coated by microarc oxidation technique for the durations of 40, 80, and 120 min. The phase composition, surface roughness and hardness of the coating were characterized by X-ray diffraction, scanning electron microscopy, profilometry. The outer region contains larger sized porosities while fine porosities were formed in the inner dense region of the coating. The longer coating duration resulted in dense inner region with finely distributed $\alpha-Al_2O_3$ precipitates. The presence of Cu in the outer region is not significant while the presence of Si in inner region was lower than in the outer region. Mullite and $\gamma-Al_2O_3$ phases were formed for 40 min and $\alpha-Al_2O_3$ phase was additionally formed for 80 min and 120 min coating time. The coating thickness increased from 38 μm (40 min) to 115 μm (120 min) while the surface roughness $(R_{a})$ increased from 5 μm (40 min) to 9 μm (120 min)

Effects of the Addition of Calcium Acetate into Silicate-Based Electrolytes on the Properties of MAO Coatings Produced on Zirconium (Acta Physica Polonica A 129, 504 (2016), ERRATUM)

The article was originally published on October 2014. In this paper "calcium acetate monohydrate" was used in electrolyte solution, however by mistake authors had written the name of the chemical as "calcium acetate tetrahydrate". The authors apologize for their error

Effects of the Addition of Calcium Acetate into Silicate-Based Electrolytes on the Properties of MAO Coatings Produced on Zirconium

Zirconium (Zr) is a potential implant material due to its excellent biocompatibility and low elastic modulus for biomedical applications. Its poor bioactivity, however, limits its use as biomaterials. In this study, microarc oxidation which is a plasma-electrochemical based process was applied to produce oxide coatings on pure zirconium. The coating processes were conducted in different electrolytes containing sodium silicate and varying amounts of calcium acetate tetrahydrate (CA) for 30 min to investigate the effect of the introduction of CA into the electrolyte solution on the morphology and chemical composition of the fabricated coatings. It was found that the coatings consisted of monoclinic-ZrO₂ and tetragonal-ZrO₂ phases. The amount of the tetragonal-ZrO₂ phase increased with the increasing CA concentration in the electrolyte. The coating thickness and surface roughness showed a tendency to increase with the increasing CA concentration in the electrolyte. It was observed that the vicinity of plasma channels were Zr-rich, while their surroundings were rich in Si and Ca elements. The outer region of the coating was denser compared to inner region consisting of Zr-rich porous structure

On the structural, microstructural and magnetic properties evolution of Ni0.5FeCoAlCrx alloys

The multicomponent alloy CoFeNiAlCr has shown great promise as a soft magnetic material due to its small coercive field and high saturation magnetisation at room temperature. By changing the ratio of the components, the Curie temperature can be tuned, along with improvements in both the coercive field and saturation magnetisation. The alloy system is interesting as the ratio of Al to Cr determines whether a single solid phase or a dual phase alloy is formed. This work has investigated the effects of Cr addition on the structural and magnetic properties of CoFeNi0.5AlCrx. It discusses the evolution of the NPs-matrix segregations and its constituents’ phases