The invention of bulk metallic glasses has stimulated extensive interest, due to their possible technological applications in a variety of industrial fields and their scientific importance in ...understanding related condensed matter physics. Among all types of BMGs, Fe-based BMGs are a unique yet important family due to their high mechanical strength, good thermal stability, strong corrosion resistance, excellent soft magnetic properties, and relatively low production costs. Since the first synthesis of the Fe-Al-Ga-P-C-B BMG reported in 1995, a vast body of literature regarding Fe-based BMGs has been published. However, until now, a full and systematic description of the development status and future prospects of Fe-based BMGs has been missing. Therefore, this article presents the research development and achievements of Fe-based BMGs in the past few decades, including their preparation, glass-forming ability, crystallization characteristics, mechanical properties, corrosion behaviors, soft and hard magnetic properties, and industrial applications. In addition, future developments of Fe-based BMGs are also proposed.
To identify the influence of microstructural variation on the X-ray diffraction intensities, X-ray diffraction patterns of hexagonal graphite (h-graphite) and turbostratic carbon (t-carbon) were ...simulated by using the general Debye equation. The numeric density of interatomic distance (NDID) is sensitive to the size and microstructure of a crystallite, so that it is used to characterize the structures of h-graphite and t-carbon. The dependence of the diffraction angles and full width at half maximums (FWHMs) of diffraction lines on the crystallite size and distortion factors is examined by computer simulation. The distortion factors for t-carbon, including rotation, translation, curvature, local positive fluctuation of interlayer spacing of graphene layers and fluctuation of atomic positions, have different influence on the NDIDs, hence on the X-ray diffraction patterns. The simulation results indicate that the diffraction angles and FWHMs of diffraction lines cannot be simply used to characterize the lattice parameters and crystallite sizes of t-carbon.
The equiatomic CrMnFeCoNi high-entropy alloy (HEA) exhibits outstanding toughness and excellent strength-ductility combination at cryogenic temperatures. However, its strength is relatively low at ...room temperature. In order to strengthen this HEA, microalloying additions of 0.8 at.% Nb and C were made and its properties and microstructure evaluated. It was found that the microalloying resulted in the formation of carbide precipitates and a reduction of the grain size to ∼2.6 μm. As a result, the room-temperature tensile yield strength (732 MPa) of the microalloyed HEA is roughly double that of the base HEA (with a concomitant increase in the ultimate strength) while its ductility is maintained at a relatively high level (elongation to fracture of ∼32%). The strengthening is due to precipitation hardening from the nanoscale carbide particles and grain refinement.
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•Nanoscale NbC particles in CrMnFeCoNi were obtained by microalloying with Nb and C.•Yield stress of NbC-added CrMnFeCoNi HEA is roughly double that of the base HEA.•The ductility of NbC-added CrMnFeCoNi HEA is maintained at a high level (∼32%).•Strengthening is due to precipitation hardening and grain refinement.
Face-centered-cubic (fcc) type high entropy alloys (HEAs) exhibit outstanding ductility even at the liquid nitrogen temperature, but they are relatively weak in strength which is far from the ...requirements for practical structural applications. One of the general concepts employed previously in alloy design is the suppression of ‘brittle’ intermetallic compound formation which usually leads to a serious embrittlement. Surprisingly, we reveal in this study that the precipitation of hard σ and μ intermetallic compounds tremendously strengthened the CoCrFeNiMo0.3 HEA but without causing a serious embrittlement. It exhibits a tensile strength as high as 1.2 GPa and a good ductility of ∼19%. A careful study of the deformation behavior reveals that the fcc matrix exhibits an extremely high work hardening exponent of 0.75, which suppresses the propagation of microcracks originated at these brittle particles. Our work presents a very successful demonstration of using complex hard intermetallic particles to manipulate the properties of fcc-type HEA systems. Furthermore, lattice distortion has been carefully measured in powder-metallurgy materials by line broadening from X-ray diffraction (XRD). It is interesting to discover that lattice planes are highly distorted in HEAs and this distortion also contributes to solid solution hardening.
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Instrumented nanoindentation was conducted on a FeCoCrMnNi high-entropy alloy with a single face-centered cubic structure to characterize the nature of incipient plasticity. Experiments were carried ...out over loading rates of 25–2500μNs−1 and at temperatures ranging from 22 to 150°C. The maximum shear stress required to initiate plasticity was found to be within 1/15 to 1/10 of the shear modulus and relatively insensitive to grain orientation. However, it was strongly dependent upon the temperature, indicating a thermally activated process. Using a statistical model developed previously, both the activation volume and activation energy were evaluated and further compared with existing dislocation nucleation models. A mechanism consisting of a heterogeneous dislocation nucleation process with vacancy-like defects (∼3 atoms) as the rate-limiting nuclei appeared to be dominant.
Summary
What is known and objectives
Different population pharmacokinetics (PPK) models of tacrolimus have been established in various populations. However, the tacrolimus PPK model in paediatric ...systemic lupus erythematosus (PSLE) is still undefined. This study aimed to establish the tacrolimus PPK model in Chinese PSLE.
Methods
A total of nineteen Chinese patients with PSLE from real‐world study were characterized with nonlinear mixed‐effects modelling (NONMEM). The impact of demographic features, biological characteristics, and concomitant medications was evaluated. Model validation was assessed by bootstrap and prediction‐corrected visual predictive check (VPC).
Results
A one‐compartment model with first‐order absorption and elimination was determined to be the most suitable model in PSLE. The typical values of apparent oral clearance (CL/F) and the apparent volume of distribution (V/F) in the final model were 2.05 L/h and 309 L, respectively. Methylprednisolone and simvastatin were included as significant.
What is new and conclusion
The first validated tacrolimus PPK model in patients with PSLE is presented.
The first tacrolimus population pharmacokinetics model in patients with paediatric systemic lupus erythematosus
A new indicator of glass-forming ability (GFA) for bulk metallic glasses (BMGs) is proposed based on crystallization processes during cooling and reheating of the supercooled liquid. The ...interrelationship between this new parameter and the critical cooling rate or critical section thickness is elaborated and discussed in comparison with two other representatives, i.e. reduced glass transition temperature
T
rg (=
T
g/
T
l, where
T
g and
T
l are the glass transition temperature and liquidus temperature, respectively) and supercooled liquid range Δ
T
xg (=
T
x−
T
g, where
T
x is the onset crystallization temperature and
T
g the glass transition temperature). Our results have shown that Δ
T
xg alone cannot infer relative GFA for BMGs while the new parameter
γ, defined as
T
x/(
T
g+
T
l), has a much better interrelationship with GFA than
T
rg. An approximation of the critical cooling rate and critical section thickness for glass formation in bulk metallic glasses is also formulated and evaluated.
Recent studies indicated that high-entropy alloys (HEAs) possess unusual structural and thermal features, which could greatly affect dislocation motion and contribute to the mechanical performance, ...however, a HEA matrix alone is insufficiently strong for engineering applications and other strengthening mechanisms are urgently needed to be incorporated. In this work, we demonstrate the possibility to precipitate nanosized coherent reinforcing phase, i.e., L12-Ni3(Ti,Al), in a fcc-FeCoNiCr HEA matrix using minor additions of Ti and Al. Through thermomechanical processing and microstructure controlling, extraordinary balanced tensile properties at room temperature were achieved, which is due to a well combination of various hardening mechanisms, particularly precipitation hardening. The applicability and validity of the conventional strengthening theories are also discussed. The current work is a successful demonstration of using integrated strengthening approaches to manipulate the properties of fcc-HEA systems, and the resulting findings are important not only for understanding the strengthening mechanisms of metallic materials in general, but also for the future development of high-performance HEAs for industrial applications.
Through controlled thermomechanical processes and microstructure, extraordinary balanced tensile properties at room temperature were achieved via formation of a high density of nanosized coherent reinforcing phase, i.e., L12–Ni3(Ti,Al), in a fcc-FeCoNiCr high-entropy alloy matrix. Display omitted
A series of six-component (FeCoNiCrMn)100−xAlx (x=0–20at.%) high-entropy alloys (HEAs) was synthesized to investigate the alloying effect of Al on the structure and tensile properties. The ...microstructures of these alloys were examined using transmission electron microscopy, and crystalline phase evolution was characterized and compared with existing models. It was found that the crystalline structure changed from the initial single face-centered cubic (fcc) structure to a duplex fcc plus body-centered cubic (bcc) structure and then a single bcc structure as the Al concentration was increased. Resulting from the structural changes there were also corresponding variations in tensile properties. In the single fcc region, alloys behaved like a solid solution with relatively low strength but extended ductility. In the mixed structure region, alloys behaved like a composite with a sharp increase in strength but reduced ductility. In the single bcc region, alloys became extremely brittle. In this study, close correlation between the microstructure and mechanical properties was also discussed and presented.
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