Matrix Refinement Research Articles

AlZn-Matrix Cast Composites Reinforced with Ti Aluminides

Doping high-zinc aluminium alloys with Ti builds in-situ composites reinforced with ternary aluminides Ti (Al,Zn)3 with a significantly grain-refined matrix. In a series of studies, Ti was introduced with Al-6 wt% Ti (AlTi6) and Zn-4 wt% Ti (ZnTi4) master alloys in amount to contribute about 3 wt% Ti in the examined alloys. The alloy microstructure has been studied using light microscopy, SEM / EDS and XRD measurements. The observed significant refinement of the alloys matrix should lead to improvement in ductility, while the in-situ reinforcement should improve tensile strength and wear properties.

Studies on Dry Sliding Wear Mechanisms of Al7075/Si3N4 Composites

Abstract In this investigation, Al7075 aluminum alloy reinforced with Si3N4 particles (3, 6, 9, and 12 wt%) was used as reinforcements to manufacture composites through a stir-casting approach. The microstructural characteristics have shown significant grain refinement owing to the presence of Si3N4 particle distribution during the solidification. SEM micrographs confirm the uniform distribution of Si3N4 particles with considerably fewer particle agglomerations throughout the matrix alloy. The reinforcement particle cluster formation is relatively increased for increasing the Si3N4 content. The SEM and EDS analyses showed good integrity at the matrix–refinement interface with no interfacial compound formation. The mechanical properties, such as hardness (up to 118 BHN), tensile strength (up to 281 MPa), and yield strength (up to 178 MPa), were enhanced by 30.69% and 20.27%, respectively. The wear-rate and coefficient of friction of the composites were evaluated with increasing percentages of Si3N4 content. The average wear-rate of the composites is 0.019, 0.0085, 0.0075, and 0.0065 mm3/m, respectively, for the increased Si3N4 ceramic particulate content from 3 to 12 wt%, while the average COF of the composites is 0.45, 0.37, 0.32 and 0.28 respectively. With the addition of Si3N4 particulate content, the wear resistance performance of the composites at 30 N has shown up to 46% enhancement and increased from 0.0052 to 0.0103 mm3/m with the increasing sliding velocity from 1.5 to 3.5 m/s for varying Si3N4 particulate content from 3 to 12 wt%, while reducing the COF up to 65%, and from 0.43 to 0.27. Different wear mechanisms are characterized by identifying the typical features of wear on the SEM micrographs of the worn surfaces. The dominant wear mechanisms of the composites are typically observed as abrasion, oxidation, delamination and melt wear. The mechanism and behavior of composites under dry sliding conditions are analyzed through the construction of wear maps. The windows of wear mechanisms and progression in terms of load and sliding velocity for the composites with various wt% of Si3N4 content were identified, analyzed, and presented.

Low-cost flash graphene from carbon black to reinforce cementitious composites for carbon footprint reduction

With the merits of high quality, cost-effectiveness, and high yield efficiency, flash Joule heating (FJH) emerges as an efficient means for mass production of flash graphene (FG). It creates prerequisites for the large-scale application of graphene in reinforcing cementitious composites, thus opening innovative possibilities for curbing carbon emissions and fostering the sustainable evolution of cementitious composites. In this study, two types of FGs, including high-purity FG (FG-G) and conductive FG (FG-D), are successfully synthesized via FJH process using carbon black as the carbon source. FG-G features a low ID/IG of 0.52, and exhibits higher graphitization and structural orderliness with fewer defects compared to the FG-D. The addition of 0.25 wt% FG-D increases the compressive strength, flexural strength, and flexural ultimate strain of cementitious composites by 16.48 MPa/16.8%, 1.43 MPa/37.2%, and nearly 2600 με/550%, respectively. The microstructure characterization results reveal that FG reduces the matrix defects, enhances both the matrix microstructure and calcium silicate hydrate gel nanostructure, which is advantageous for matrix refinement, inhibition of microcrack aggregation and propagation, and load transfer efficiency. Its disorderly stacked turbine structure also contributes to robust interface bonding and friction with cement matrix, thus facilitating the strengthening and toughening of cementitious composites. This study introduces a potential avenue to develop widely applicable and versatile silicon-based cementitious composites with high performance and low CO2 emission by using small carbon-based graphene as reinforcement.

Effect of curing regimes on mechanical properties and microstructure of engineered cementitious composites with full desert sand

To establish a curing regime that facilitates the rapid enhancement and stable progression of early-age strength and tensile ductility in engineered cementitious composites with full desert sand (DSECC), aligning with production efficiency, this study examines the effects of different curing regimes (standard curing, natural curing, 20℃ water curing, and 90℃ water bath curing) on DSECC 's the mechanical properties and microstructure. The findings indicate that 90℃ water bath curing is beneficial to enhance the mechanical properties of DSECC, and its early 7 days strength and tensile deformation capacity (up to 7.05 %) can reach or exceed the standard curing 28 days level. In the uniaxial tensile test, samples cured in 20℃ water exhibit increased crack widths and reduced crack numbers, resulting in a sharp decline in the ultimate tensile strain from 4.96 % at 14 days to 1.57 % at 28 days. Natural curing leads to regression in strength at 28 days. The microstructure analysis revealed that 90℃ water bath curing fostered the development of high-density C-S-H gel and the dissolution of desert sand, while preserving the integrity of the fibers, enhancing the fiber-matrix interface transition zone (ITZ). The pore characteristic parameters under 90℃ water bath curing are superior, which has a notable refinement of the DSECC matrix's pore size. 20℃ Water curing can make up for the defects caused by desert sand and improve the compactness of matrix-aggregate ITZ. Natural curing yields the lowest degree of matrix hydration, with porosity reaching as high as 41.90 %, and pores smaller than 50 nm accounting for only 8.97 %.

Hybrid effect of graphite and carbon fibers on thermal properties of copper/graphite/carbon fibers composites

To maintain the high thermal conductivity (TC) and reduce the coefficient of thermal expansion (CTE) of conventional copper (Cu)/graphite composites, novel Cu/graphite/carbon fibers (CFs) hybrid composites were designed by replacing part of graphite with Cu-coated CFs and prepared by spark plasma sintering (SPS) process. The incorporation of CFs resulted in increased interface density, reduced twin boundaries, and significant grain refinement of the Cu matrix. TEM observations revealed that the Cu-coating on surfaces of CFs enhanced the interfacial bonding between CFs and Cu matrix. The Cu-coated CFs can act as connecting channels between graphite particles, which partially compensate the negative effect on TC. Furthermore, strong interfacial bonding and large Cu/CFs contact areas contribute to the reduction in CTE. As a result, the Cu/30%graphite/10%CFs composite showed TC and CTE of 453.5 Wm−1 K−1 and 10.9 × 10−6 K−1, respectively. Compared to the Cu/40%graphite composite, the CTE of Cu/30%graphite/10%CFs composite was reduced by ∼20 % with only 4.4 % sacrifice in TC. Consequently, the Cu/graphite/CFs hybrid composites showed an excellent balance between TC and CTE, which are superior to the conventional Cu/graphite and Cu/CFs composites. The findings of this work provide new insights for designing and preparing new thermal management materials.

Selective laser melting of the ternary NiTi+3Cu shape memory alloys with excellent properties via microstructural tailoring

The ternary NiTi+3Cu parts were produced using selective laser melting (SLM) with the addition of 3 wt% Cu nanoparticles. The incorporation of Cu nanoparticles resulted in the precipitation of nano-sized Ti2Cu second phase, the refinement of B2 matrix, the elimination of texture, and a transition from columnar to equiaxed grains. The SLM-fabricated NiTi+3Cu parts exhibited excellent antibacterial properties, achieving an antibacterial rate of 70.83 % due to the persistent release of Cu ions. The NiTi+3Cu deposits demonstrated stable tensile performance in both the transverse and longitudinal directions, and they performed better than their NiTi counterparts, primarily due to the effects of B2 grain refinement and the presence of nano-sized Ti2Cu precipitates. As the B2 phases transformed from columnar to equiaxed grains, the anisotropic rate of ultimate tensile strength and elongation to fracture was reduced from 16.3 % to 1.64 % and 16.1–3.07 %, respectively. Furthermore, the wear resistance was also enhanced by the incorporation of Cu nanoparticles, and the wear mechanism shifted from abrasive to delamination wear. These findings indicate that the crack-free ternary NiTi+3Cu shape memory alloys can be fabricated using SLM, synchronously achieving excellent antibacterial, mechanical, and wear properties through microstructural tailoring.

Enhanced high temperature performance of two-scale network-structured (TiB+Ti5Si3)/TA15 composites by simultaneous adjustment of matrix and nano-scaled Ti5Si3

To improve the high temperature performance of the titanium matrix composite, solution and aging treatments were carried out on the (TiB + Ti5Si3)/TA15 composite with a two-scale network structure. The microstructure evolution during the heat treatment and high temperature performance at 650 °C were investigated. It is found that a fine matrix with basket-weave structure and nano-scaled Ti5Si3 can be obtained through a proper combination of solution and aging treatment. Optimal high temperature performance is achieved with yield strength and ultimate tensile strength improved by 15 % and 24 % respectively without sacrificing ductility. Matrix refinement is attributed to network-distributed TiB and fine martensite after solution treatment. During subsequent aging, fine secondary α phase and β phase are formed and then grow. The growth mechanisms of the secondary α phase and β phase are phase boundary migration and grain coalescence. The main strengthening mechanisms are boundary strengthening of the matrix and the precipitation strengthening of Ti5Si3, which are mainly related to the thickness of the secondary α phase and the fraction of Ti5Si3, respectively.

Coarse-to-Fine Homography Estimation for Infrared and Visible Images

Homography estimation for infrared and visible images is a critical and fundamental task in multimodal image processing. Recently, the coarse-to-fine strategy has been gradually applied to the homography estimation task and has proved to be effective. However, current coarse-to-fine homography estimation methods typically require the introduction of additional neural networks to acquire multi-scale feature maps and the design of complex homography matrix fusion strategies. In this paper, we propose a new unsupervised homography estimation method for infrared and visible images. First, we design a novel coarse-to-fine strategy. This strategy utilizes different stages in the regression network to obtain multi-scale feature maps, enabling the progressive refinement of the homography matrix. Second, we design a local correlation transformer (LCTrans), which aims to capture the intrinsic connections between local features more precisely, thus highlighting the features crucial for homography estimation. Finally, we design an average feature correlation loss (AFCL) to enhance the robustness of the model. Through extensive experiments, we validated the effectiveness of all the proposed components. Experimental results demonstrate that our method outperforms existing methods on synthetic benchmark datasets in both qualitative and quantitative comparisons.

Microanalytical Mass Spectrometry with Super-Resolution Microscopy Reveals a Proteome Transition During Development of the Brain's Circadian Pacemaker.

During brain development, neuronal proteomes are regulated in part by changes in spontaneous and sensory-driven activity in immature neural circuits. A longstanding model for studying activity-dependent circuit refinement is the developing mouse visual system where the formation of axonal projections from the eyes to the brain is influenced by spontaneous retinal activity prior to the onset of vision and by visual experience after eye-opening. The precise proteomic changes in retinorecipient targets that occur during this developmental transition are unknown. Here, we developed a microanalytical proteomics pipeline using capillary electrophoresis (CE) electrospray ionization (ESI) mass spectrometry (MS) in the discovery setting to quantify developmental changes in the chief circadian pacemaker, the suprachiasmatic nucleus (SCN), before and after the onset of photoreceptor-dependent visual function. Nesting CE-ESI with trapped ion mobility spectrometry time-of-flight (TOF) mass spectrometry (TimsTOF PRO) doubled the number of identified and quantified proteins compared to the TOF-only control on the same analytical platform. From 10 ng of peptide input, corresponding to <∼0.5% of the total local tissue proteome, technical triplicate analyses identified 1894 proteins and quantified 1066 proteins, including many with important canonical functions in axon guidance, synapse function, glial cell maturation, and extracellular matrix refinement. Label-free quantification revealed differential regulation for 166 proteins over development, with enrichment of axon guidance-associated proteins prior to eye-opening and synapse-associated protein enrichment after eye-opening. Super-resolution imaging of select proteins using STochastic Optical Reconstruction Microscopy (STORM) corroborated the MS results and showed that increased presynaptic protein abundance pre/post eye-opening in the SCN reflects a developmental increase in synapse number, but not presynaptic size or extrasynaptic protein expression. This work marks the first development and systematic application of TimsTOF PRO for CE-ESI-based microproteomics and the first integration of microanalytical CE-ESI TimsTOF PRO with volumetric super-resolution STORM imaging to expand the repertoire of technologies supporting analytical neuroscience.

The Effect of Mono and Hybrid Additives of Ceramic Nanoparticles on the Tribological Behavior and Mechanical Characteristics of an Al-Based Composite Matrix Produced by Friction Stir Processing.

Friction stir processing (FSP) is an effective method for incorporating ceramic nanoparticles into metal matrix composites. This study investigated the effects of single and multiple additions of BN, VC, and SiC nanoparticles on the microstructure refinement and tribological behavior of an AA2024 alloy-based nanocomposite matrix fabricated by FSP. The results showed that adding ceramic nanoparticles, either singly or in combination, led to significant refinement of grain structure and improved wear resistance of the AA2024 alloy-based nanocomposite matrix. Additionally, the study found that combining BN, SiC, and VC nanoparticles produced the most effective effects on refining and reducing grain size. The microhardness behavior of the composite surface resulting from the hybrid particles showed a significant improvement, reaching 94% more than the base alloy. Overall, these results indicate that the multiple additions of ceramic nanoparticles by FSP are a promising approach to improve aluminum alloys' tribological behavior and mechanical properties.

Fabrication of osteogenesis induced WE43 Mg-Hydroxyapatite composites with low biodegradability and increased biocompatibility for orthopedic implant applications

Good biocompatibility, low biodegradation rate and excellent mechanical properties are essential for desirable performance of metallic biomaterials during osseointegration process. In the present study, bioabsorbable WE43 Mg alloy was used for fabrication of bio-composites with addition of nanosized hydroxyapatite (HA) particles by means of multi pass friction stir processing (FSP) for orthopedic implant applications. Microstructure, in vitro biodegradation and biocompatibility, wettability, and microhardness of resultant bio-composites were characterized. Results showed that applying severe plastic deformation through FSP caused significant grain refinement of Mg matrix and homogenous dispersion of fragmented secondary phase particles. Moreover, applying higher number of FSP passes increased uniformity of distribution of HA nanoparticles throughout Mg matrix. Compared to coarse grain samples, grain refined samples showed lower Mg2+ concentration and H2 evolution in simulated body fluid (SBF). Moreover, addition of HA into Mg matrix, reduced Mg2+ release and H2 evolution. The bio-composites illustrated uniformly and flatly corroded surface compared to samples without HA nanoparticles. During immersion of the bio-composites in SBF solution, a cauliflower structure of Ca–P compounds deposited on the surface of bio-composites which confirmed acceptable biomineralization. Contact angle measurement demonstrated that wettability of fabricated bio-composites increased by increasing number of FSP passes. Mouse osteoblast MC3T3 cell culture indicated that the fabricated bio-composites with uniform distribution of HA nanoparticles showed excellent in vitro biocompatibility, cell viability, and cell proliferation. Eventually, it was found that applying further FSP and presence of HA nanoparticles resulted in increased microhardness which is an indication of higher load-bearing capability of the fabricated bone implants.

Microstructure and mechanical properties of WC-TiC0.4 composites doped with ZrO2 or 3Y-ZrO2

The ZrO2 or 3Y-ZrO2 incorporated WC-TiC0.4 composites were consolidated employing spark plasma sintering (SPS) technology at different temperatures. The impacts of ZrO2 and 3Y-ZrO2 as toughening agents on the densification, phase composition, microstructure and mechanical properties of the WC-based composites were assessed. The results revealed that the WC-5 wt% TiC0.4–9 wt% ZrO2 (W5Ti9Zr) composite required a lower sintering temperature of 1700 °C for nearly full densification than WC-5 wt% TiC0.4–9 wt% 3Y-ZrO2 (W5Ti9Zr-3Y) composite. The diffraction peaks of monoclinic ZrO2 (m-ZrO2) existed only in the W5Ti9Zr composite. The evenly dispersed ZrO2 and 3Y-ZrO2 achieved the relatively homogeneous and fine microstructure in W5Ti9Zr and W5Ti9Zr-3Y composites. Moreover, the semi-coherent interfaces of (W1-x, Tix)Cn layer with WC, (W1-x, Tix)Cn layer with m-ZrO2, and (W1-x, Tix)Cn with m-ZrO2 brought about a rise in the fracture toughness of W5Ti9Zr composite. The W5Ti9Zr composite yielded the better comprehensive mechanical properties with a combination of hardness (20.8 GPa) and fracture toughness (9.9 MPa·m1/2) as compared to those of W5Ti9Zr-3Y composite. Furthermore, the main toughening mechanisms of W5Ti9Zr and W5Ti9Zr-3Y composites included grain refinement of WC matrix, a mixed transgranular and intergranular fracture, stress-induced transformation of t-ZrO2 to m-ZrO2, and crack deflection.

Microstructure and mechanical properties of laser beam welding joint of in-situ (ZrB2+Al2O3)/AA7N01 nanocomposites

In this paper, in-situ nanoparticles ZrB2 and Al2O3 are introduced to raise the mechanical properties of AA7N01 Laser beam welding (LBW) joint by in-situ melt reaction method. The effects of ZrB2 and Al2O3 nanoparticles on the microstructure and tensile properties of in-situ (ZrB2+Al2O3)/AA7N01 nanocomposites and LBW joints were studied. The experimental results indicate that ZrB2 nanoparticles provide more nucleation sites for grain nucleation and tend to aggregate at the grain boundary (GB). The average grain size of composites is greatly refined from about 110 μm to 20 μm. As the content of particles increased from 1 vol% to 3 vol%, the ultimate tensile strength (UTS) of nanocomposites is enhanced from 439.3 MPa to 538.2 MPa, the UTS of the LBW joint is increased from 246.7 MPa to 353.6 MPa. The effects of ZrB2 and Al2O3 nanoparticles on grain refinement and growth of matrix are analyzed. Furthermore, the strengthen mechanism induced by the precipitates and nanoparticles on the mechanical properties of composites and joints are also discussed.

Artificial Intelligence

The article forms a matrix of the main propositions and markers of artificial intelligence in non-professional (philistine) discourses. The study is implemented on the Internet using special tools. The subject of the analysis is the search queries in the main ‘Google’ and ‘Yandex’ services, thematic communities, social networks and users’ comments. The definition of the matrix of non-professional stereotypical labeling of artificial intelligence as an actual developing technology allows us to see a picture of a new metaphysics. “Technological” metaphysics is inextricably linked with mythological thinking and significantly affects the absorption of scientific and technological developments. It also influences the constructive critical attitude towards the physical condition. The article substantiates that this modern technical mythology, which includes many speculative assumptions, has a double meaning: on the one hand, it “domesticates” technology, and on the other hand, it creates an insurmountable barrier for the convergence of spiritual and religious scope and the scientific worldview. The definition and subsequent refinement of the mythological matrix is necessary for the effective implementation of innovative programs, adjustment of those to the education system, constructive dialogue between the state, scientists, and users.

Decomposable pairs and construction of multiwavelets

We study the construction of refinable function vectors and multiwavelets from the perspective of decomposable pairs. There exists a pair of matrices known as the decomposable pair, associated with a refinement mask of the form H(ξ)=12∑k=0lHke−iξk, which gives the spectral information about H(ξ). We show that the existence of a solution to a matrix refinement equation is related to the dimension of 1-eigenspace of the square matrix in the decomposable pair. We also show that the existence of a refinement mask with sum rules of order 1 is related to the dimension of (−1)-eigenspace of the square matrix in the decomposable pair. A systematic procedure is developed to create refinement masks satisfying the sum rules of order 1 using decomposable pairs, such that the corresponding matrix refinement equation has a solution. Several examples are provided to illustrate the theoretical results obtained.

Enhancement in hardness and corrosion resistance of directed energy deposited 17–4 PH martensitic stainless steel via heat treatment

Directed energy deposition (DED) process involves complex cyclic reheating and rapid cooling, which probably lead to differences in microstructure and corrosion resistance from the wrought alloys. In the present study, the pitting corrosion resistance of 17–4 PH martensitic stainless steel component fabricated by wire-arc DED technique under as-fabricated and post-processing heat treated (1050 °C for 1 h + H900 aging) conditions were investigated. The pitting corrosion resistance was significantly improved after post-processing heat treatment as reflected by a noble shift in pitting potential from 230 to 490 mVSCE. This is mainly attributed to the formation of the reversed austenite (3%), precipitation of the nano-sized face-centered cubic (fcc) Cu particles as well as the refinement of martensitic matrix. However, a lower repassivation ability was observed as the precipitation of CrNbN, resulting in a N depletion region nearby. Simultaneously, a micro-galvanic couple was created between the CrNbN and nearby region, which promoted initiation of the pits surrounding the particles. This work illustrates that post-processing heat treatment is an effective way to improve the corrosion resistance of the wire-arc DEDed 17–4 PH stainless steel and the precipitation of CrNbN should be carefully controlled due to its detrimental effect on the repassivation ability.

Microstructure and mechanical properties of multi-scale α-Fe reinforced Cu–Fe composite produced by vacuum suction casting

Cu–10Fe composites were produced by the vacuum suction casting and traditional vacuum mold casting, respectively. The evolution of microstructure and properties of the composites during cold rolling and aging processes was analyzed. Compared with the traditional mold-casted Cu–Fe composites, the suction-casted Cu–Fe composite had better mechanical properties, with microhardness, tensile strength and elongation of 146 HV, 526 MPa and 23.7%, respectively. The softening temperature of the suction-casted Cu–Fe composite was 520 °C, which was 220 °C higher than that of traditional mold-casted Cu–Fe composite. The good performance of the suction-casted Cu–Fe composite was mainly attributed to the refinement of the Cu matrix and the formation of the multi-scale α-Fe particles caused by the effect of solute trapping during vacuum suction casting. The yield strength of the composites was mainly attributed to the contribution of Orowan strengthening, refinement strengthening and dislocations strengthening, which count for 31.1%, 25.8% and 24.1%, respectively.

High-Accuracy DOA Estimation Based on an Improved Sample Correlation Matrix

In a direction-finding process, high-resolution subspace-based algorithms are the most popular ones. It is well-known that their performance of direction of arrival estimation mainly depends on the accuracy of the signal subspace. However, the traditional methods of capturing the signal subspace do not mine the information hidden in the array output in depth, which may restrict their application to some extent. In this study, we elaborate on a novel scheme to extract the signal subspace through refinement of the correlation matrix of the array output. In the developed scheme, a collection of spatial temporal correlation matrices is firstly established. Then, we define a weighting vector for the correlation matrices, and take the weighted average of the correlation matrices as the covariance matrix of the array output. It is clear that this covariance matrix is more general than the traditional covariance matrix, and the signal subspace can be optimized through adjustment of the weighting vector. In this study, we present an optimal weighting vector by adopting the particle swarm optimization. Simulation results demonstrate that the proposed approach has better performance in root mean square error compared to the existing schemes.

Standard pairs and construction of multiwavelets using refinement masks satisfying sum rules of order one

A multiwavelet is typically constructed starting from a vector-valued function satisfying a matrix refinement equation. The approximation order of such a refinable function vector is related to the sum rules of order [Formula: see text] satisfied by the corresponding refinement mask. A refinable function vector can be obtained using cascade algorithm by constructing a refinement mask which satisfies the sum rules of order [Formula: see text] A standard pair associated with a refinement mask gives information about its spectral properties. In this paper, we present a procedure for constructing refinement masks satisfying the sum rules of order [Formula: see text], starting from standard pairs. How this helps in the construction of asymmetric multiwavelets using standard pairs is illustrated through examples. A sufficient condition on a standard pair and a necessary and sufficient condition on a left standard pair are established so that the corresponding refinement mask satisfies the sum rules of order [Formula: see text].

Achieving improved strength and ductility through multi-pass cold deformation and annealing of a Cu-Zn-Bi alloy

In this work, a simple-yet-powerful processing method was applied successfully to a Bi-containing brass alloy (Cu–30wt.%Zn–3wt.%Bi), which utilized multi-pass proper annealing following medium-strain cold-rolling deformation. Both strength and ductility of the alloy have been improved simultaneously. This is mainly due to the redistribution of the bulky Bi phase along the rolling plane as well as the grain refinement of the brass matrix. Bi phase pancaking reduces the possibility of cracking at the early stages during straining whilst grain size refines continuously cycle-by-cycle, and the matrix is strengthened. The processing method could be applied to other alloys with similar microstructure.