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The die casting defects and tensile properties of high pressure die cast (HPDC) Mg‐Zn‐Al‐RE alloys with various combinations of Zn and Al were studied. The results show that die casting defects in Mg‐Zn‐Al‐RE alloys are affected by the percentage of Zn and Al contents. The hot tearing susceptibility (HTS) of Mg‐Zn‐Al‐RE alloys tends to increase with increasing Zn content up to 6 wt%, while a further increase of Al and/or Zn content reduces the HTS. In tensile tests, the yield strength (YS) is generally improved by increasing Zn or Al content, whereas the tensile strength (TS) and ductility appear to depend largely on the presence of casting defects. Compared with Mg‐Zn‐Al alloys, the mechanical properties of the Mg‐Zn‐Al‐RE alloy are significantly improved. The Mg‐4Zn‐4Al‐4RE alloy is found to have few casting defects and the optimal tensile properties.

In this paper, the machinability of a near beta Ti25Nb3Mo3Zr2Sn titanium alloy with different heat treatment histories has been investigated in terms of cutting force, chip temperature and chip formation. A solution treatment was performed followed by ageing at different temperatures for the near beta alloy. It has been shown that the same alloy behaves differently during machining at various cutting speeds after different heat treatments. The observations have been explained in terms of friction effects and the hardness of the materials. It has been concluded that the ductility of a workpiece plays a significant role in determining its machinability. High friction at the tool–chip interface in a ductile workpiece resulted in a higher degree of chip segmentation and a larger undeformed surface length in each chip.

The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigated. The effects of laser processing and milling parameters on cutting forces and tool wear have been examined. It is found that local heating and softening of the workpiece by the laser beam in front of the cutting tool significantly reduced the cutting forces, especially the force in the feed direction during up-cut milling. Laser power, tool–beam distance, depth of cut and cutting speed are the parameters influencing the change of feed force during laser-assisted milling. Analysis of the workpiece temperature rise due to laser beam heating shows that the feed force is strongly dependent on the workpiece temperature in front of the cutting zone; significant reduction of feed force occurred when the temperature in front of thecutting zone was in the range 200–450°C. Edge chipping is found to be the tool failure mode for both conventional milling and laser-assisted milling. A significant improvement in tool life during laser-assisted milling was obtained when the workpiece temperature in front of the cutting zone was at an optimum value. Compressed air was used to remove the chip from the cutting tool, which made the milling process more effective. The optimum workpiece temperature in front of the cutting zone with compressed air delivered through the spindle is about 350°C, higher than that with compressed air delivered through a stationary nozzle (about 230°C). The maximum tool life in the former case is much longer than that in the latter case.

Machining titanium is challenging due to its low thermal conductivity which results in very high temperatures at the tool/workpiece interface and in addition there is a tendency for titanium to react with most cutting materials, resulting in surface and subsurface deformation in the workpiece. This paper investigates the relationship between vibration and surface deformation that occurs while machining commercially pure titanium and Ti6Al4V alloy materials under both wet and dry machining conditions. The results have demonstrated that vibration monitoring (normalised peak frequency amplitude) can be used as a predictive tool for optimising the surface quality of the machined workpiece. Twinning plays a prominent role in the subsurface of the machined Grade 2 material.

The effect of HIPping on the mechanical properties and microstructure of a cast Ti-6Cr-5Mo-5V-4Al alloy have been investigated. In the cast condition, the alloy predominantly consists of coarse β grains. In comparison to the HIPped samples, it exhibits poor mechanical properties, in particular low ductility, due to large amounts of remnant porosity. HIPping at 740°C substantially reduces the amount and size of porosity, while HIPping at 820°C and 900°C virtually eliminates all porosity, significantly improving the mechanical properties.

In this study the effects of different aging heat treatments on the properties and microstructure of a high strength, high toughness metastable β Ti, BTi-6554 (Ti-6Cr-5Mo-5V-4Al), have been compared. An initial β phase solution treatment was followed by aging at moderate temperatures in the α/β dual phase zone by either step aging directly from the solution treatment temperature or by quenching to room temperature prior to the aging heat treatment. The differing heat treatment methods have significant effects on the microstructure and mechanical properties.

MCrAlY can serve as stand-alone overlay coatings or bond coats in thermal barrier coating systems, and its properties play a vital role in determining the performance of these coating systems. In order to further understand the behavior of MCrAlY coatings, several NiCoCrAlY model alloys with different levels of Re (0.3 wt%, 6 wt%, and 9 wt%) were investigated. Microstructural observation showed the addition of Re promoted the precipitation of Cr-rich phases, such as α-Cr and σ. The presence of α-Cr lowered the coefficient of thermal expansion (CTE) of the coating alloys, which could reduce the CTE mismatch at the scale-metal interface. The solid solution strengthening effect of Re is responsible for an increase in Rockwell hardness of the coating alloys. But the isothermal oxidation resistance at 1100°C was deteriorated due to the precipitation of brittle α-Cr phase, a phase of inferior oxidation resistance compared with β-NiAI and γ-Ni. [ABSTRACT FROM AUTHOR]

Molten, commercially pure aluminum has been treated ultrasonically with differing input power. The results show that the ultrasonic power can significantly refine the microstructure of the aluminium and increase the hardness of the samples. A mathematical model developed in this paper can predict the effect of the ultrasonic power on the grain size of the pure aluminium well.

Three binary Fe-based alloys Fe-S, Fe-Si, and Fe-Mn has been designed and melted in order to investigate the effect of static magnetic field on the migration behavior and distribution of the three elements during the solidification process in this study, and microstructure and chemical composition on the samples have been inspected by optical microscopy and Original Position Analysis technologies. It has been found that the magnetic field can effectively change the distribution of S, Si and Mn, and the migration behaviors of the three elements are different.

Pulsed electric field has been effectively used to control and modify the solidification process in castings. In this study, a pulsed electric field at 8 volts and 19 kHz has been applied to Fe-P, Fe-S, and Fe-Si binary alloys, and microstructure and elements distribution of the three alloy samples have been inspected. The results indicated that P migrated from cathode to anode while S and Si migrated from both electrodes to the center under the pulsed electric field during the solidification process.

A pulsed electric current (19 kHz, 0-8 volts) has been applied to a molten Fe-0.5C-1.5Mn alloy to investigate its effect on the microstructure and the distribution of carbon and manganese. It has been shown that the pulsed electric field can improve the microstructure from a coarse banded structure to a compact acicular structure by increasing the pulsed voltage from 4 volts to 8 volts. The pulsed electric treatment also has an effect on the C and Mn distribution with a tendency for C and Mn to migrate to the cathode.

The microstructures of laser welds of the near-β titanium alloy TLM were studied for substrates in the as hot rolled, solution treated and solution treated and aged conditions. Irrespective of substrate condition the fusion zone consists of a cellular β structure. Trends in bulk hardness of the various conditions seem to be carried through into the weld consistently across the profile. The hardness in the fusion zone remained similar to that of the bulk. However, a drop in hardness occurs in the HAZ. Lath that formed around the hardness indent of the fusion zone and HAZ suggest that the weld undergoes a martensitic transformation to α" during deformation.

Grain refinement of titanium alloys during solidification is believed to have many benefits for processing and properties. Recent work has emphasized the importance of solute elements in grain refining cast titanium and it was demonstrated that the growth restriction factor is useful for predicting the grain refining effectiveness of solute elements in titanium. Despite oxygen being the major impurity element present in titanium alloys and having been previously identified as a theoretical growth restricting solute, its effect as a β-grain refiner is still unexplored. This paper investigates the effect of oxygen on the grain size in cast titanium alloys.

The trace element Zr was added to an Al-Mg alloy to investigate its effects on microstructure and warm formability of aluminium sheets. Microstructural examination showed that the Zr addition resulted in an elongated grain structure due to inhibitedrecovery and recrystallization by Al3Zr particles during thermomechanical treatments. In order to evaluate the warm formability, warm tensile tests were carried out at temperatures ranging from 275 to 350°C, and at strain rates ranging from 0.015 to 1.5 s-1. The results showed that the addition of Zr increased the flow stress but decreased the ductility at most test conditions. At a low strain rate of 0.015 s-1, the addition of Zr resulted in low ductility at 350°C but high ductility at 275°C.The effect of Zr additions on warm formability is discussed on the basis of the microstructural changes.

The hot deformation behaviour of the alpha / beta Ti-6Al-4V alloy was investigated at various temperatures and strain rates by means of compression and torsion tests. As expected, the peak flow stress increased with increasing strain rate and decreased as the initial sample temperature was increased. The different flow behaviours observed are discussed in terms of the volume fraction of each phase. The dual phase Ti-6Al-4V alloy was assumed to be a composite material containing a soft phase and a hard phase. By taking into consideration the phase-to-phase interaction and volume fraction change with temperature, constitutive models are proposed to simulate the deformation behaviours. By application of the rule of mixtures the modelled yield stresses showed good agreement with the experiment results.

The elastic response of a metastable β titanium alloy, Ti-25Nb-3Zr-3Mo-2Sn, is characterised. The effects of processing and heat treatment on phase composition and mechanical behaviour are reported. The alloy exhibits pseudoelastic behaviour which is related to the reversible formation of the stress induced α" phase. The solution treated condition displays the greatest pseudoelasticity and the hot rolled condition the least. Tensile deformation reduces the modulus of the alloy. This is due to increases in the relative proportions of the low modulus α" phase.

A metastable β titanium alloy, BTi-6554 (Ti-6Cr-5Mo-5V-4Al) has been developed for structural applications in aircraft because of its high strength, high toughness, and good fatigue properties. This paper reports on the effect of heat treatment on microstructure and microhardness of the alloy. It has been shown that in the as hot rolled condition, the alloy consists of a single β phase. Heat treatment between 450-750˚C results in the precipitation of α laths, while exposure to temperatures between 700-800˚C results in the gradual transformation of the α phase back to β phase with larger grain sizes resulting from higher heat treatment temperatures.

Development of microstructure in chips during machining of Grade 2 titanium at different cutting speeds has been investigated. The morphology of the chip changes from continuous chip to irregular and regular segmented chip with increasing cutting speed. The deformation in continuous and segmented chips is characterized as continuous and localized shear respectively. The deformation mechanism in the irregular segmented chip is the dislocation slip in the continuous region and twinning around the localized shear. Deformation twinning was observed inside the segment between the shear bands in the regular segmented chip. These deformation twins are responsible for the hardening inside the segment.

Production, sustainment and repair technologies for light alloy components in the defence applications account for a significant proportion of Defence Materials Technology Centre (DMTC) activities. Key challenges in this regard include the affordable manufacture and repair & sustainment of Titanium components for new and legacy platforms. The DMTC research program portfolio incorporates collaborative technology development activities between industry and the research sector within a framework of a partnership model that includes input from the Defence customer on likely procurement opportunities for industry, and longer term strategic requirements of Defence. The technological focus is particularly on the benchmarking of strategies, technologies and manufacturing techniques associated with the manufacture of aerospace components via high speed machining. Developing affordable, cost-effective and best of breed machining processes and practices among a broad range of Australian manufacturing organisations is a key goal of the DMTC. This paper describes an initiative of the DMTC focused on developing and optimising engineering capability in metals manufacturing for aerospace applications. Data generated from a range of participating sources conducting machining trials of identical titanium and stainless steel components is compared and contrasted in the context of best practice development.

This paper presents a feasible machining test to measure, compare and predict the machinability of different titanium alloys. A drilling test was developed and investigated on the two most common grades of titanium, commercial purity and Ti6Al4V. The experiments and analysis revealed that tool wear followed a characteristic pattern for all machining conditions investigated. When machining Ti6Al4V, tool life was shorter and cutting forces higher compared with commercial purity Ti. Paradoxically, despite the more difficult machining, Ti6Al4V samples had better surface integrity than commercial purity samples. A procedure was developed that could be incorporated into a real-time process monitoring device to warn of imminent tool failure.

The microstructure and mechanical properties of a cast near β type titanium alloy, Ti-25Nb-3Zr-3Mo-2Sn, have been investigated in this paper. In the as cast condition, the alloy possesses coarse, equiaxed β grains and Transmission Electron Microscopy(TEM) observations showed the ω phase is also present in this condition. The alloy in the as cast condition has low strength and is highly ductile. Direct ageing at 450°C for 4 hours leads to the formation of a large number of fine scale α phase precipitates. The alloy in the aged condition is less ductile but exhibits significantly enhanced strength.

Grain refinement of cast titanium alloys is believed to have many benefits. However, literature on how to control and manipulate β-grain size during the solidification of cast components is scarce. This paper discusses the current state of research in grain refining practices in cast titanium alloys.

The effects of alloy chemistry and heat treatment on the microstructure and mechanical properties of Ti-Nb-Zr-Mo-Sn near  type titanium alloys have been investigated. Near β titanium alloys consisting of non-toxic alloying elements Mo, Nb, Zr, Sn possess a low Young’s modulus, and moderate strength and plasticity. As the hot rolled TLM alloy (Ti-25Nb-3Zr-3Mo-2Sn) possesses high strength and low Young’s modulus a detailed investigation is performed for this alloy. Solution treatment of the hot rolled TLM alloy reduces strength and increases ductility without affecting the Young’s modulus. Ageing of the solution treated TLM alloy reduces elongation and increases the Young’s modulus with little change in strength. Both solution treated and aged conditions show features of two stage yielding associated with a strain induced martensitic transformation.

This paper outlines the current state of research into laser welding of titanium and its alloys for medical applications. The differences that exist between the medical and other industries are described and a direction for advancing research in this field is proposed.

Removal of heat from the cutting zone is critical when machining titanium. The application of high pressure coolant during turning of titanium results in longer tool life and better surface finish. In this paper, the effect of the application of cutting fluid at high pressure during the milling of titanium alloys is presented.

The effect of machining speed during dry machining of commercial purity titanium was investigated on the surface roughness, residual stress and depth of deformation along with changes in the microstructure of the deformed subsurface layer. Both optical analysis and TEM examination of the microstructure have shown (see the figure) that twining is a dominant mechanism of subsurface deformation during dry machining.

This paper describes the application of a new in‐cavity thermal measurement method to determine the interfacial heat transfer coefficient during high pressure die casting of aluminium A380 alloy and the magnesium alloy AZ91D. These measurements enabled the accurate determination of heat flux densities and interfacial heat transfer coefficients and the rapid evolution of these values with time during high pressure die casting of these alloys.

In this work acoustic monitoring was performed while machining Ti6Al4V with a variety of process parameters. The surface integrity of the components was characterized using microstructural examination and hardness and surface roughness measurements. It is shown that a simple measure of the acoustic spectrum (see figure) can be used to relate operationally induced vibration to the surface integrity of the machined part.

The transformation of Bocar Automotive Products from an aluminium products fabricator to an innovative manufacturer supplying automakers with accessory product systems has required the adaptation of forming processes and product capabilities to address the relatively small volumes in the Australian market, strategic change in the company’s target markets and cultural change in its internal operations. The strategy for developing new capability in the casting and forming of aluminium alloy products has taken place over 5 years beginning with the bending of extruded shapes, progressing into the forming of sheet aluminium alloys and the casting of bumper bar components, and finally into the integration of these processes into bumper systems for a number of 4 Wheel Drive models. This paper describes the product design, metal forming and production changes that Bocar has introduced and integrated with its marketing strategy to become a recognized innovator in the accessories market in Australia.

Ti6Al4V alloys are considered difficult materials to machine, especially at high cutting speeds due to their low thermal conductivity and specific heat which causes high localized cutting temperatures at the tool-workpiece interface. For these reasons machining titanium alloys usually results in excessive tool wear and its low modulus promotes chatter. This regenerative vibration or chatter is a significant problem. In the investigation reported here, vibration monitoring has been used to optimise machining processes by correlating machining process parameters with vibration severity. Machining experiments were carried out under wet and dry machining conditions while vibrations were measured and analysed. The results have demonstrated that the application of a vibration monitoring system can be an important tool to increase machining speed.

Hydrogen sulfide (H2S) is a neuromodulator in the brain and a relaxant for smooth muscle. H2S protects primary cortical neurons from oxidative stress by increasing the intracellular concentrations of glutathione, the major antioxidant in cells. However, changes in glutathione alone are not sufficient to account for full protection in all types of nerve cells. H2S is here shown to protect an immortalized mouse hippocampal cell line from oxidative glutamate toxicity by activating ATP-dependent K+ (KATP) and Cl− channels, in addition to increasing the levels of glutathione. The present study therefore identifies a novel pathway for H2S protection from oxidative stress.

It has been suggested that a receptor for advanced glycation end products (RAGE) is the nerve cell receptor for amyloid β protein (Aβ). To determine if this is indeed the case, two neural cell lines as well as rat cortical neurons were examined for the presence of the mRNA for RAGE by PCR and northern blot analysis. Although lung was strongly positive, in no case was RAGE mRNA detected in the cultured neural cells. Glycated albumin is a major ligand for RAGE and the cell surface RAGE protein is trypsin sensitive. In agreement with the mRNA data, trypsin treatment did not alter Aβ toxicity, nor did glycated albumin modify the Aβ response. It follows that RAGE is not the neural receptor for Aβ.

beta-Amyloid protein (A beta) is a member of a small group of proteins that accumulate as amyloid deposits in various tissues. It has recently been demonstrated that the toxicity of A beta toward some neural cells is caused by oxidative damage. Since all of the amyloid diseases are characterized by protein deposited in the antiparallel beta-sheet conformation, it was asked whether there is a common toxic mechanism. It is shown here that the protein components of other human amyloidoses, including amylin, calcitonin, and atrial natriuretic peptide, are all toxic to clonal and primary cells. The toxicity is mediated via a free radical pathway indistinguishable from that of A beta. Experiments with synthetic peptides suggest that it is the amphiphilic nature of the peptides generated by their beta structure rather than their beta structure per se that causes toxicity. These results tend to rule out the alternative that amyloid toxicity is exclusively mediated via specific cell surface receptors.

3D sand mould printing using binder jet technology can enable many technical improvements in casting practice, including part consolidation, design of parts to optimise the consumption of materials and hazardous chemicals, and on-demand and flexible size part manufacturing near the customer. Incorporating artificial intelligence in optimising the design of moulds, printing process parameters, and solidification processes may help automate a production facility and reduce labour time. Elimination of hazardous chemicals from industrial use may be a challenge. Therefore, an alternative technology to fuse the sand particles during printing or an environmentally friendlier alternative option for the binders and other consumables should be utilised with the 3D sand printing process. Properties of parts produced using 3D printed sand moulds have the potential to be better than the properties of parts produced using traditional casting due to this technology's benefits. This technology is an enabling technology for traditional casting processes rather than a competing technology. It is causing a paradigm shift in casting design because of the mould geometries achievable by using additive manufacturing to produce the sand mould. This paper reviews the first twenty years of research and challenges in developing 3D sand printing processes as an innovation for sustainable manufacturing.

Segregation defects, known as β-flecks, have long detracted from the widespread use of metastable β-Titanium alloys produced via solidification routes. These defects form when segregated β-stabilising solute such as chromium create localised phase instabilities which is detrimental to the alloy’s aging response and mechanical properties. This work explores whether Additive Manufacturing is a viable process for preventing the formation of these defects in the Beta-C alloy (Ti-3Al-8V-6Cr-4Mo-4Zr). Although it is observed that β-flecks initially form during deposition of the top layer, each new subsequent layer and thermal cycle promotes solid-state diffusion of alloy elements that effectively heals the segregation defect. Additive Manufacturing is thus a promising pathway for producing high quality metastable β-titanium alloys free of this defect.

Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining (LAM) of titanium alloys. These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life. This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process. The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.

Ti-6Al-4V is the single most important Ti alloy, accounting for use in almost 60% of all the applications of Ti materials. Additive manufacturing (AM) offers design freedom with regard to Ti-6Al-4V for creation of high-quality, customized products. However, the large-scale development of this technology is constrained by the high raw material costs. In this study, a method based on ball milling powder modification was proposed to convert low cost, non-spherical hydrogenated-dehydrogenated Ti (HDH-Ti) powder into spherical, printable Ti powder. Following mechanical mixing, the ball-milled HDH-Ti powder was further blended with elemental powders of aluminum and vanadium to develop low-cost HDH Ti-6Al-4V. Simultaneously, the issue pertaining to high oxygen associated with HDH Ti-6Al-4V was addressed via introduction of yttrium. A cost-affordable, high-performance AM Ti-6Al-4V alloy was finally developed via laser-based powder bed fusion of metals (PBF-LB/M) after printing parameter optimization and heat treatment. The AM-prepared Ti-6Al-4V demonstrated a relative density of 99.3%, an ultimate tensile strength of ~1083 MPa, and an elongation of 9%, comparable to those obtained using costly pre-alloyed powders. Further, numerical simulation and detailed microstructural characterization were performed to reveal the underlying mechanism. Powder modification, compositional modulation, and laser in-situ alloying were the three essential techniques used as part of this approach for optimizing the mechanical properties of the Ti-6Al-4V alloy. Overall, this method demonstrates excellent potential in terms of mitigating the high cost. Moreover, it may further promote research on AM of a variety of Ti alloys besides Ti-6Al-4V.

A magnesium alloy containing essential, non-toxic, biodegradable elements such as Ca and Zn has been fabricated using a novel twin-roll casting process (TRC). Microstructure, mechanical properties, in vivo corrosion and biocompatibility have been assessed and compared to the properties of the rare earth (RE) element containing WE43 alloy. TRC Mg-0.5 wt% Zn- 0.5 wt% Ca exhibited fine grains with an average grain size ranging from 70 to 150 μm. Mechanical properties of a TRC Mg-0.5Zn-0.5Ca alloy showed an ultimate tensile strength of 220 MPa and ductility of 9.3%. The TRC Mg-0.5Zn-0.5Ca alloy showed a degradation rate of 0.51 ± 0.07 mm/y similar to that of the WE43 alloy (0.47 ± 0.09 mm/y) in the rat model after 1 week of implantation. By week 4 the biodegradation rates of both alloys studied were lowered and stabilized with fewer gas pockets around the implant. The histological analysis shows that both WE43 and TRC Mg-0.5Zn-0.5Ca alloy triggered comparable tissue healing responses at respective times of implantation. The presence of more organized scarring tissue around the TRC Mg-0.5Zn-0.5Ca alloys suggests that the biodegradation of the RE-free alloy may be more conducive to the tissue proliferation and remodelling process.

This work investigates the influence of Ag (1 wt%) on the mechanical properties, in vitro and in vivo corrosion, and biocompatibility of Fe‐35Mn. The microstructure of Fe‐35Mn‐1Ag possesses a uniform dispersion of discrete silver particles. Slight improvements in compressive properties are attributed to enhanced density and low porosity volume. Fe‐35Mn‐1Ag exhibits good in vitro and in vivo corrosion rate of Fe‐35Mn due to an increase in microgalvanic corrosion. Gas pockets, which originate from an inflammatory response to the implants, are observed in the rats after 4 weeks implantation but are undetectable after 12 weeks. No chronic toxicity is observed with the Fe‐35Mn‐1Ag, suggesting acceptable in vivo biocompatibility. The high corrosion rate of the alloy triggers an increased level of nonadverse tissue inflammatory responses 4 weeks after implantation, which subsequently subsides at 12 weeks. The Fe‐35Mn‐1Ag displays properties that are suitable for orthopedic applications. This paper reports on the in vivo biodegradability and biocompatibility of Fe‐35Mn‐1Ag. The study confirms both the excellent biocorrosion and biocompatibility of the sintered alloy, suggesting its good suitability in orthopedic applications. This is also likely the first report on in vivo gas evolution associated with a biodegradable Fe alloy implant.

Novel microstructural features were found in the Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS). Examination of the microstructure showed that the fabricated sample exhibits a layered morphology with arced deposit boundaries. Novel distributions and morphologies of various phases including β, α, α'' and ω were detected in the LENS-manufactured part which substantially differ to conventionally processed alloy counterparts. The β grains and subgrains spread over multiple deposits and layers, aligned to the build direction, forming a complex network microstructure comprising large highly textured columnar grains aligned to β phase <001> orientations. The α precipitates have needle-like shapes and are widely distributed across a majority of the deposited layers, whereas the nanoscale ω particles were present in regions absent of α precipitation. Localised, massively transformed α'' phase with a very long and curved rod-like shape and substantial surface defects was identified. The formation of these novel microstructural features is investigated and discussed in the context of the characteristics of the LENS fabrication process. The microstructures are attributed to the complex thermal history in the unique deposit-by-deposit and layer-by-layer method employed during LENS additive manufacturing in conjunction with the complex precipitation behaviours exhibited by TiNb-based alloys. The characteristics and formation mechanisms of the LENS-manufactured Ti−Nb−Zr−Mo−Sn alloy microstructures revealed here provide a basis to optimize LENS and post-LENS heat treatment processes to optimize microstructures for improved performance.

A process to dealloy a Ti-3Zr-2Sn-3Mo-25Nb (TLM) titanium alloy to create a porous surface structure has been reported in this paper aiming to enhance the bioactivity of the alloy. A simple nanoporous topography on the surface was produced through dealloying the as-solution treated TLM alloy. In contrast, dealloying the as-cold rolled alloy created a hierarchical micro/nanoporous topography. SEM and XPS were performed to characterize the topography and element chemistry of both porous structures. The roughness, hydrophilicity, protein adsorption, cell adhesion, proliferation, and osteogenic differentiation were tested. The elements of Zr, Mo, Sn, and Nb were depleted at the nanoporous TLM surface with a diameter of 15.6 ± 2.3 nm. Dissolving the microscale α phase from the alloy surface contributed to the formation of the microscale grooves on the surface. The simple nanoporous topographical surface exhibited hydrophilicity and higher protein adsorption ability, which facilitated the early adhesion of osteoblasts compared with the hierarchical micro/nanoporous surface. On the other hand, the hierarchical micro/nanoporous surface improved cell proliferation and differentiation and still retained the contact guidance function, which implied good bonding for osseointegration. This research revealed the effect of phase composition on the surface morphology of dealloying titanium alloy and the synergistic effect of micron and nanometer topography on the function of osteoblasts. This paper therefore provides insights into the surface topological design of titanium-based biomaterials with improved biocompatibility.

Extracorporeal membrane oxygenation (ECMO) is used in critical care to manage patients with severe respiratory and cardiac failure. ECMO brings blood from a critically ill patient into contact with a non-endothelialized circuit which can cause clotting and bleeding simultaneously in this population. Continuous systemic anticoagulation is needed during ECMO. The membrane oxygenator, which is a critical component of the extracorporeal circuit, is prone to significant thrombus formation due to its large surface area and areas of low, turbulent, and stagnant flow. Various surface coatings, including but not limited to heparin, albumin, poly(ethylene glycol), phosphorylcholine, and poly(2-methoxyethyl acrylate), have been developed to reduce thrombus formation during ECMO. The present work provides an up-to-date overview of anti-thrombogenic surface coatings for ECMO, including both commercial coatings and those under development. The focus is placed on the coatings being developed for oxygenators. Overall, zwitterionic polymer coatings, nitric oxide (NO)-releasing coatings, and lubricant-infused coatings have attracted more attention than other coatings and showed some improvement in in vitroand in vivoanti-thrombogenic effects. However, most studies lacked standard hemocompatibility assessment and comparison studies with current clinically used coatings, either heparin coatings or nonheparin coatings. Moreover, this review identifies that further investigation on the thrombo-resistance, stability and durability of coatings under rated flow conditions and the effects of coatings on the function of oxygenators (pressure drop and gas transfer) are needed. Therefore, extensive further development is required before these new coatings can be used in the clinic.

The additive manufacturing of metallic lattices based on triply periodic minimal surfaces (TPMS) has recently received plenty of interest in the field of hard tissue engineering. Although these structures are deemed to present advantages over conventional designs in regard to their biological and compressive mechanical properties, their fatigue life has received little attention. In the following work, Ti–6Al–4V lattices based on gyroid, diamond and Schwartz primitive unit-cells were tested in quasi-static tension and tension-tension cyclic fatigue. Their resulting elastic and fatigue properties are reported and compared in the context of biomedical applications. Compared to the two others, the Schwartz lattices were found to have the lowest strength for a similar relative density. The Young’s moduli of the three samples however, were of similar magnitude. Basquin’s functions are presented to fit the fatigue S–N curves and these can assist with the fatigue design of lattices with identical unit-cells. Fractography analysis from scanning electron microscopy images revealed that the fatigue crack initiation always occurs at the surface, pointing out the importance of surface treatment in SLM-produced titanium lattices.