Nickel-coated carbon nanotubes (Ni-CNTs) were achieved by electroless plating. Laser cladded IN718 and IN718 with 10, 30, and 50 wt% additions of Ni-CNTs were fabricated. The structural evolution of CNTs in the laser-deposited layers was studied; the microstructure, tensile, and wear properties of the laser-cladded alloys were characterized. The results show that CNTs in the laser-deposited layers are mostly transformed to carbon nanoproducts (CNPs) in the forms of graphene nanosheets, graphene fragments, carbon nanoribbons, and diamond-like nanoparticles by unzipping, interbonding, collapsing, and curvature of CNTs. The interdendritic Laves phase formation is dramatically depressed due to the addition of Ni-CNTs, but the excess addition of the Ni-CNTs can undesirably increase the formation of NbC. The addition of Ni-CNTs effectively improves the tensile and wear properties. The most superior tensile and wear properties are achieved in the layers with 30 and 50 wt% additions of Ni-CNTs, respectively. The generation of intermetallic phase and CNPs are revealed to be two dominant effects both on the tensile and wear properties of the laser-cladded alloys.

Two rapidly solidified (RS) Mg ribbons with the compositions of Mg97Zn2Gd1 and Mg90Zn5Gd5 (at.%) were first prepared by the planar flow casting method. These RS ribbons were subsequently consolidated by spark plasma sintering (SPS). The use of SPS on the RS ribbons was demonstrated to be an effective processing route to control W-phase precipitation process while keeping fine grains. The size of W-phase particles was less than 200 nm in Mg97Zn2Gd1 alloy and smaller than 500 nm in Mg90Zn5Gd5 alloy. The content of W phase was approximately 34 vol% and 41 vol% in the two SPS bulks, respectively. The compressive properties showed that the yield compressive stress (YCS) and ultimate compressive stress of the Mg97Zn2Gd1 alloy reached 200 MPa and 390 MPa, respectively, and an elongation of 0.24. The corresponding values for the Mg90Zn5Gd5 alloy were 313 MPa, 504 MPa, and 0.14, respectively. Based on the results of the quantitative analysis, W-phase nanoparticles with size less than 100 nm exhibited obviously strengthening effect in the Mg alloys. It highlighted that the W-phase nanoparticles contributed a large proportion of the YCS in the Mg97Zn2Gd1 alloy and a relatively small proportion for that of the Mg90Zn5Gd5 alloy.

Ternary Al–15 wt% Cu–7 wt% Si and Al–22 wt% Cu–7 wt% Si alloy specimens were generated by transient directional solidification (DS) and rapid solidification (RS) techniques. The microstructures are constituted by an α-Al dendritic matrix surrounded by two eutectic, that is, a binary eutectic (Si + α-Al) and a bimodal eutectic, consisting of cellular-type binary eutectic colonies (α-Al + Al2Cu) in a ternary eutectic matrix consisting of α-Al + Al2Cu + Si. The bimodal eutectic exists at cooling rates from 0.5 to 250 K/s. The secondary dendritic spacing, λ2, of the DS samples varied from 5 to 20 μm and from 10 to 18 μm for both examined alloys. The λ2 from 2.7 to 4.0 μm characterized the RS samples. Mechanical properties have been determined for various samples related to different dendritic spacing values. Based on the evaluation of the rapidly solidified microstructures, it was possible to assess the cooling rates.

The effect of cooling rate on the phase composition of gas atomized Raney type catalysts was studied using the Ni-75 at.% Al composition. The resulting particles were sieved into 3 standard size fractions and analysed using XRD with Rietveld refinement: as expected the three phases, Al₃Ni₂, Al₃Ni, and Al-Al₃Ni eutectic were identified. Differing phase compositions in the 3 size ranges were identified offering a possible explanation for varying catalytic activity with cooling rate, the higher cooling rates experienced by the smaller droplets allow less time for the peritectic conversion of Al₃Ni₂ to Al₃Ni to proceed. This in turn results in a more Al-rich residual liquid, increasing the volume fraction of eutectic. This was further confirmed when analysing the microstructure using SEM backscatter imaging. Al₃Ni₂ was found to be encased in a shell of Al₃Ni characteristic of peritectic reactions. The remainder of the alloy was found to consist of Al-Al₃Ni eutectic. The SEM backscatter imaging also indicated that the larger particles displayed and a more globular structure than smaller particles. Similar Raney type Ni-75 at.% Al doped with 1.5 at.% Cr were synthesised using the same method and sieved into the same 3 standard size fractions. It was found that the Cr doped alloys exhibited a more dendritic character than the undoped samples in the corresponding size fraction, although the material still displayed an increasingly dendritic character with increasing cooling rate. The phase composition found by Rietveld refinement also followed a similar trend to the undoped samples with decreasing amounts of Al₃Ni formed at the higher cooling rates. However, significant amounts of an additional phase, Al₁₃Cr₂, were also observed. Rietveld refinement found that a larger amount of Al₁₃Cr₂ was present than could be accounted for by the addition of 1.5 at.% Cr . This can be explained by the substitution of Ni onto the Cr lattice, as confirmed by Rietveld refinement. Al₁₃Cr₂ was found to be located mostly at the boundary of the Al₃Ni and Al-Al₃Ni eutectic phases during elemental mapping and quantitative image analysis of backscattered electron micrographs. This indicates that precipitation of Al₁₃Cr₂ is towards the end of the solidification process. The relatively large amounts of the Al-rich Al₁₃Cr₂ may explain the enhanced catalytic activity observed following leaching of Cr-doped Raney catalysts.

Liquid phase analysis dominates the field of blood diagnostics and requires drawing blood volumes of several ml for each test. To achieve acceptable accuracy, each single liquid blood test requires ∼7 mL per blood sample, and repeated blood tests are often needed. Frequent testing ca result in Hospital Acquired Anemia for infants, chronically ill, and critically ill patients. Blood testing methods that can be utilized with small amounts of blood are a critical need to save lives. Theranos claimed to have developed novel methods requiring only a few nL of blood. However, Theranos’ techniques led to errors that exceeded beyond the medically acceptable threshold of 10%. This work investigates solid state blood analysis using low volumes of several µL. The most common blood tests used as first line for diagnostics and monitoring patients’ status, always include blood electrolytes, iron, and in some cases, heavy metals.

The present work investigates the formation of rapidly solidified Homogeneous Thin Solid Films (HTSFs) formed from blood drops, in order to make them suitable for solid state analysis in vacuo and in air. The solidification of ∼5 micro-liter (µL)-sized blood droplets into HTSFs is studied with two goals: achieve reproducible HTSFs optimized for producing accurate analysis, and successfully measure the potential accuracy of measurements made on HTSFs for blood electrolytes Na, K, Mg, Ca, and Cl and heavy metals such as Fe.

The blood volumes selected for this work are in the µL range, one thousandth volumes drawn for current liquid phase analysis. Balanced Saline Solution (BSS) is used as an initial liquid for testing solidification uniformity and a potential calibration material. Next, canine and human blood are studied on two types of HemaDropTM coatings for solidification: super-hydrophilic and hyper-hydrophilic. HTSF formation from BSS and blood drops are compared on both coated and uncoated surfaces.

Three solid state analytical methods are investigated in parallel to probe composition at different depths and test each for reproducibility and accuracy: Ion Beam Analysis (IBA), X-ray Fluorescence (XRF), and X-ray Photoelectron Spectroscopy (XPS). The results show that using solid films of blood yields composition, which can be reproducibly measured by IBA, XPS and XRF to varying degrees. XPS’s depth of analysis, limited to ∼5 nm, probes a small fraction of the HTSF, but provides insights into the range of thickness for homogeneous compositions in HTSFs. Statistical and error analysis help establish whether measurements taken in sets of three typically used in lab fall below the medically accepted error threshold (<10%) for each technique and element detected. Measurements are repeated and taken at various locations and on different HTSFs to establish reproducibility. XRF is of particular interest, because it is fast, accurate, portable and can be conducted in air, making it ideal for areas with limited resources.

Because of rapid solidification involved in the laser or e-beam based additive manufacturing (AM) process, solution treatable metallic parts made by these methods usually possess a unique nonequilibrium microstructure which changes significantly during subsequent thermal treatment. Such evolution alters the size, morphology, length scale, and distribution of microstructural features and has a substantial impact on thermal properties and possibly on electrical properties as well. This study focuses on effects of microstructural evolution on thermal properties of an additively manufactured AlSi10Mg part. The changes of thermal properties such as thermal expansion, heat capacity, thermal diffusivity, and thermal conductivity as a function of thermal treatment are reported. The results show that the formation of supersaturated primary α aluminum and unique cellular structure imparted by fast solidification in the AM process are the major cause for the low thermal diffusivity and low thermal conductivity observed in this solution treatable, as-built part. A correlation between microstructural evolution and changes in thermal properties is established. Advantages and tailoring of the thermal properties of additively built parts are discussed. Implications of these results are important for other additively manufactured components based on popular solution treatable alloys.

Ti–Al alloys are established as promising candidates for aerospace applications due to their lightweight, good elevated temperature strength, and decent corrosion resistance. In this study, a Ti–51Al (at.%) alloy is fabricated by spray deposition. The effects of temperature and strain rate on the deformation behavior of the spray-deposited Ti–Al alloy are investigated. The microstructural evolution of the Ti–Al alloy with different deformation temperatures is discussed in detail. A strain-dependent constitutive equation was proposed to predict the flow stresses at the elevated temperatures for the spray-deposited Ti–Al alloy. The microstructure of the as-deposited Ti–51Al alloy exhibits a α2/γ lamellar-structure with average size 25 ± 2 μm, due to the high cooling rate observed during solidification. The lamellar structure is embedded on a γ matrix. The amount of the α2/γ lamellar-structure reduces gradually with increasing the hot deformation temperature. After hot isostatic pressing at 1523 K, the microstructure is mainly comprised of the γ matrix.

The powder-bed laser additive manufacturing (AM) process is widely used in the fabrication of three-dimensional metallic parts with intricate structures, where kinetically controlled diffusion and microstructure ripening can be hindered by fast melting and rapid solidification. Therefore, the microstructure and physical properties of parts made by this process will be significantly different from their counterparts produced by conventional methods. This work investigates the microstructure evolution for an AM fabricated AlSi10Mg part from its nonequilibrium state toward equilibrium state. Special attention is placed on silicon dissolution, precipitate formation, collapsing of a divorced eutectic cellular structure, and microstructure ripening in the thermal annealing process. These events alter the size, morphology, length scale, and distribution of the beta silicon phase in the primary aluminum, and changes associated with elastic properties and microhardness are reported. The relationship between residual stress and silicon dissolution due to changes in lattice spacing is also investigated and discussed.

The shear-band propagation in bulk metallic glasses (BMGs) during deformation plays a key role in determining their macroscopic ductility. In this work, the shear band propagation during plastic deformation was investigated in the Cu46Zr46Al8 BMG and its in situ or ex situ prepared BMG composites. Compared with the brittle BMG, both types of ductile BMG composites show a more stable shear banding behavior as revealed by a larger power-law scaling exponent obtained from statistical analysis of serrations recorded in compressive curves. A higher cut-off elastic energy density (δc) linked with the multiplication of shear bands is observed for the in situ prepared BMG composites. However, the ex situ fabricated BMG composites show an almost equivalent or slightly larger δc since the dominant shear band but not multiple shear bands mainly governs their deformation. Such observations imply that the shear banding stability of BMGs during deformation is enhanced not only by inducing multiple shear bands but also by obstructing the movement of the dominant shear band at its driven path.

Metal additive manufacturing (AM) processes, such as selective laser melting (SLM), enable powdered metals to be formed into arbitrary three-dimensional shapes. For aluminum alloys, which are desirable in many high-value applications for their low density and good mechanical performance, SLM is regarded as challenging due to the difficulties in laser melting aluminum powders. However, a number of recent studies have demonstrated successful aluminum processing, and have gone on to explore its potential for use in advanced AM componentry. In addition to enabling the fabrication of highly complex structures, SLM produces parts with characteristically fine microstructures that yield distinct mechanical properties. Research is rapidly progressing in this field, with promising results opening up a range of possible applications across scientific and industrial sectors. This article reports on recent developments in this area of research and highlights key topics that require further attention.

Short pulse laser irradiation has the ability to bring a material into a state of strong electronic, thermal, phase, and mechanical nonequilibrium and trigger a sequence of structural transformations leading to the generation of complex multiscale surface morphologies, unusual metastable phases, and microstructures that cannot be produced by any other means. In this article, we provide an overview of recent advancements and existing challenges in the understanding of the fundamental mechanisms of short pulse laser interaction with materials, including the material response to strong electronic excitation, ultrafast redistribution and partitioning of the deposited laser energy, the peculiarities of phase transformations occurring under conditions of strong superheating/undercooling, as well as laser-induced generation of crystal defects and modification of surface microstructure.

Ultrafast laser synthesis and processing of materials is a burgeoning field that is still in its infancy. This article and the theme articles in this issue review recent developments in the fundamental physics of ultrafast laser–solid interactions as well as the state of our understanding of ultrafast laser-driven surface morphology, modification of transparent media, 3D photo-polymerization and additive fabrication, spallation of graphene, and biological interactions. Also reviewed is the current state of emerging commercial high average power lasers, central to the widespread adoption of ultrafast laser synthesis and processing of materials. It is remarkable that ultrafast lasers with 20 to 600 femtosecond pulse duration can have such a dramatic impact on materials. As we learn more about the fundamental mechanisms that drive the ultrafast laser-material response, even more applications are anticipated to emerge. This revolutionary approach to materials synthesis and processing has already spawned several commercial technologies and promises to create many more in the near future.

Rapid solidification of Al30Si70 alloy was studied via electromagnetic levitation technique. The solidification kinetics and the morphology of the solidification front of the Si phase were analyzed in situ by using a high-speed video camera and subsequent microstructural analysis of as-solidified samples. It shows that solidification of the sample always starts from one point. After that, nucleation continues to proceed at the interface front during growth. The morphology of primary Si transforms from faceted wafer to nonfaceted equiaxed grain and the grain size decreases with increase of undercooling. At small undercooling, the growth velocity of primary Si decreases with time and the floated Si wafers have a trend to agglomerate, while at large undercooling, the nucleation rate decreases with time, which are explained by the fact that silicon content, undercooling and density at the solid–liquid interface change with time in solidification. Finally, the nucleation rate and growth velocity were discussed in combination of classical theory.

An innovative model based on spinodal-like decomposition of supercooled multi-component liquids was developed for prediction of the glass forming ability (GFA) of ternary alloys. The up-hill diffusion in the initially homogeneous freezing ternary liquid was considered as a necessary condition for solidification of crystalline phases. New generalized criteria of spinodal decomposition of ternary alloys for time/space correlated fluctuations were formulated. These criteria take into account both thermodynamic and kinetic properties of the system. The introduced criteria were found to provide adequate GFA evaluation of different compositions in the Mg-based ternary alloys.

The influence of cooling rates on the solidification and microstructure of rapidly solidified quasicrystal alloys with a nominal compositions of Mg57Zn37Y6 (at.%) prepared by melt spinning method was investigated. The microstructure, phase constitution, phase transition, and phase structure of the alloys were examined by means of scanning electron microscopy, x-ray diffraction, energy dispersive spectrometer, differential scanning calorimetry, and transmission electron microscopy. The results show that rapid solidification refines and homogenizes the microstructure of Mg57Zn37Y6 alloys, compared to the conventionally-cast master alloy. With the increasing cooling rate of rapid solidification, the thickness of the ribbon decreases greatly and a larger amount of I-phase can be formed. α-Mg, MgZn, and icosahedral phases are found in the as-cast alloy, but the MgZn phase is absent from rapidly solidified alloys. The I-phase in both as-cast and rapidly solidified alloys can precipitate directly from the melt during the solidification process. A higher cooling rate can lead to a large degree of supercooling, resulting in a decreased phase transition temperature and a large number of icosahedral short-range orders (ISROs). ISROs can act as templates in liquid and promote the nucleation of I-phase.

In this work, the effects of different preparation methods on the microstructures and properties of the Ti45.7Zr33Ni3Cu5.8Be12.5 alloy were systematically studied by both experimental and numerical ways. It is found that the heating methods and the cooling rate during the process of preparation have great influences not only on the morphology and crystalline structure of the solid solutions but also on the thermal stability of the amorphous phase. Furthermore, the different crystalline structures and micromorphologies of the ductile phase will also influence the mechanical properties. And the uniaxial compression tests at room temperature verify that the Ti45.7Zr33Ni3Cu5.8Be12.5 samples obtained by different preparation methods possess different degrees of plasticity. The better comprehensive properties were found for samples with a larger size under the copper mold cooling conditions. The variation of the morphology of the solid solution phase under different preparation conditions is believed to be the vital factor that leads to the diversity in properties.

We present a strain-free, self-assembled GaAs nanodots on GaAs(001) surfaces. Nanodots are studied by atomic force microscopy and field emission scanning electron microscopy. Nanodots self-assemble on the GaAs surface when two laser pulses overlap on the surface interferentially. Their stoichiometry is characterized by energy dispersive X-ray spectroscopy in the electron microscope. For the stoichiometry study, electrons with voltages less than 5 kilovolts were used to produce the characteristic X-rays from dots in order to enhance the surface sensitivity. The stoichiometric analysis indicates that the nanodots’ relative composition ratio of Ga over As reaches to that of GaAs substrate when the dot size becomes smaller than 100 nm. The chemical analysis suggests a novel route of strain-free semiconductor nanodots.

We study how the period of transient thermal gradient impacts on morphologies of nanostructures on the Si(001) surface. Strain-free, self-assembled nanodots as well as periodic nanowires are fabricated directly on Si(001) surfaces by applying high power laser pulses on the surface interferentially. The morphologies of the nanostructures are studied by atomic force microscopy. Generally, the laser irradiated surfaces show nanowires but nanodots are also observed. The nanowire width increases with interference period. The narrowest nanowires observed have the width smaller than 50 nm, which is four times smaller than the interference period while the nanodots have a base width of 43 nm and height of 8 nm.

We presented the investigation on the cooling rate dependent undercooling of the microsized and nanosized Bi droplets in the Zn matrix via differential fast scanning calorimetry at scanning rates ranging from 300 to 6000 K/s. The experimental results demonstrated that the embedded nanosized Bi droplets gave more reproducible undercooling measurements than that of microsized Bi droplets at the grain boundaries. In addition, different cooling rate dependences of undercooling of microsized and nanosized Bi droplets were found. When the cooling rate is increased from 300 to 6000 K/s, the undercooling of the embedded nanosized Bi droplets increased gradually from 125 to 130 K. However, for microsized Bi droplets at the grain boundaries, there was an obvious increase of undercooling when the cooling rate was higher than 2000 K/s. In other words, the undercooling evolution displayed a sigmoidal relationship with the increase in cooling rate, indicating the change of the heterogeneous nucleation mechanism from a surface-induced mode to a volume-induced one.

Heusler Ni–Mn–(Ga, In, Sn, Sb) materials can provide large magnetic-field-induced strain, giant magnetocaloric and magnetoresistance effects based on their first-order solid-state martensitic transformation. In the present work, effects of Co doping on martensitic transformation behavior in melt-spun Ni–Mn–Sn ribbons were studied by x-ray diffraction, scanning/transmission electron microscopy, and thermal analysis. Experimental results showed that both martensitic transition and austenite Curie temperatures increased linearly with Co addition to Ni49Mn39Sn12; and meanwhile, crystal structures of the martensite evolved from four-layered orthorhombic (4O) to five-layered orthorhombic (10M), and then seven-layered monoclinic (14M). The compositional dependence of the martensitic transition temperatures was well correlated with changes of valence electron concentration (e/a) and unit-cell volume of high-temperature austenite. It was proposed that both increase of valence electron concentration and shrinkage of austenite unit-cell volume with Co addition are favorable to the occurrence of martensitic transformation. In addition, the Curie temperature of austenite increases with Co addition, which was ascribed to the enhancement of ferromagnetic exchange interaction.